Performance information

• Analysis of two-step photocurrent generation in GaAs:N-based intermediate band solar cells with utilization of device simulation
  Md Faruk Hossain; Shuhei Yagi; Hiroyuki Yaguchi
  AIP Advances, Volume：15, Number：2, Feb. 2025, [Reviewed]
  We developed a novel approach to analyze the two-step photocurrent generation process in intermediate band solar cells (IBSCs) by means of numerical device simulation combined with rate equation analysis. An IBSC having a GaAs:N intermediate band (IB) absorber with the same layered structure as experimentally investigated in our previous work is modeled, and its characteristic behavior of external quantum efficiency (EQE) is successfully simulated with the utilization of Silvaco-Atlas software. The simulated results gave new insights into the material parameters of the device, such as trap states and interface recombination velocity, and revealed that an electron-blocking layer adjacent to the IB absorber plays a significant role in confining the electrons in the IB state, which is the main prerequisite for efficient two-step photocurrent generation. Change in EQE (ΔEQE) induced by additional light illumination of which energy is below the valence band–IB gap is analyzed as an evaluation metric of two-step photocurrent generation based on a rate equation analysis. The integrated electron concentration in the GaAs:N absorber layer is calculated from the simulation results and is used as an input parameter for the rate equation analysis. As a result, the bias voltage-dependent ΔEQE of experimentally investigated IBSC is well reproduced, indicating that the proposed method can be a useful approach for a better understanding of IBSC operation physics and designing more efficient devices.
  AIP Publishing, Scientific journal
  DOI：https://doi.org/10.1063/5.0247676
  DOI ID：10.1063/5.0247676, eISSN：2158-3226
• Spontaneous Heterointerface Modulation by a Methylammonium Tetrafluoroborate Additive for a Narrow-Bandgap FAPbI₃ Photoabsorber in Perovskite Solar Cells
  Daisuke Kubota; Ryuzi Katoh; Hiroyuki Kanda; Hiroyuki Yaguchi; Takurou N. Murakami; Naoyuki Nishimura
  ACS Applied Materials & Interfaces, Volume：16, Number：40, First page：53918, Last page：53929, Sep. 2024, [Reviewed]
  American Chemical Society (ACS), Scientific journal
  DOI：https://doi.org/10.1021/acsami.4c11784
  DOI ID：10.1021/acsami.4c11784, ISSN：1944-8244, eISSN：1944-8252
• Estimation of Junction Temperature in Single 228 nm‐Band AlGaN Far‐Ultraviolet‐C Light‐Emitting Diode on c‐Sapphire Having 1.8 mW Power and 0.32% External Quantum Efficiency
  Muhammad Ajmal Khan; Mitsuhiro Muta; Kohei Fujimoto; Javier Gonzalez Rojas; Pablo Fredes; Ernesto Gramsch; Yasushi Iwaisako; Hiroyuki Yaguchi; Hideki Hirayama
  physica status solidi (a), Volume：221, Number：21, May 2024, [Reviewed]
  The increasing resistance of methicillin‐resistant Staphylococcusaureus to antibiotics is a major challenge faced by mankind in thehistory of medical science and according to United Nations, 700‐000 patients worldwide die every year from an infection with multidrug‐resistant organisms (MROs). Aluminum gallium nitride‐based 228 nm Far‐ultraviolet‐C (Far‐UVC) lightsources can be safely used as a germicidal application in both manned as wellas in unmanned environments against these MROs. Previously, the 228 nm Far‐UVC light‐emitting diode (LED) with emission power of 1 mW was reported by ourgroup, however, the value of external quantum efficiency (EQE) was not reportedusing conventional thick Ni (20 nm)/Au (100 nm) p‐electrode. Herein, animproved Far‐UVC LED on c‐Sapphire is attempted using a special technique in SR4000 type of metal‐organic chemical vapor deposition reactor to control the Al composition in n‐AlGaN buffer and across the 2 inch‐wafer. As a result, the light emission power of 1.8 mW and EQE of 0.32% in 228 nm Far‐UVC LED aresuccessfully achieved using very thin p‐electrode (Ni/Au). However, arelatively high junction temperature of ≈100°C around thejunction of Far‐UVC LED is observed. Finally, some simple heat‐sink modules forheat dissipation of Far‐UVC LED panel with light power of 30 mW are implemented.
  Wiley, Scientific journal
  DOI：https://doi.org/10.1002/pssa.202400064
  DOI ID：10.1002/pssa.202400064, ISSN：1862-6300, eISSN：1862-6319
• Nitrogen Concentration Dependence of Two‐Step Photocurrent Generation by Below‐Gap Excitation in GaPN Alloys
  Abdul Qayoom; Shuhei Yagi; Hiroyuki Yaguchi
  physica status solidi (b), Volume：261, Number：4, Feb. 2024, [Reviewed]
  Two‐step photocurrent generation and its dependence on nitrogen concentration in GaPN alloys using two‐wavelength excited photocurrent (TWEPC) measurements are investigated. External quantum efficiency (EQE) measurements show an increase in the two‐step absorption of below‐gap excitation light through tail states at longer wavelengths and that the quasi‐direct gap redshifts as the nitrogen concentration increases. The improvement in the EQE at longer wavelengths is explained by the increased density of the tail states in GaPN with higher nitrogen concentrations. In contrast, the EQE decreases at shorter wavelengths with increasing nitrogen content. TWEPC results show that differential photocurrent density , which shows the synergy effect of multiple‐wavelength light, reduces with the addition of nitrogen. It is found from rate–equation analysis that the decrease in the EQE at shorter wavelengths and in is mainly due to the increased nonradiative recombination in GaPN with higher nitrogen concentration. The use of lattice‐matched alloys and a p‐type GaP capping layer as well as the optimization of the growth conditions can improve the EQE at shorter wavelengths and .
  Wiley, Scientific journal
  DOI：https://doi.org/10.1002/pssb.202300369
  DOI ID：10.1002/pssb.202300369, ISSN：0370-1972, eISSN：1521-3951
• Photocurrent enhancement by below bandgap excitation in GaPN
  Abdul Qayoom; Sanjida Ferdous; Shuhei Yagi; Hiroyuki Yaguchi
  Japanese Journal of Applied Physics, Volume：62, Number：SK, First page：SK1038, Last page：SK1038, May 2023, [Reviewed]
  Abstract
  
  This study presents two-wavelength excited photocurrent (TWEPC) measurements in GaP_1−xN_x grown by metalorganic vapor phase epitaxy. TWEPC measurements reveal that photocurrent generation is significantly enhanced when above gap excitation and below gap excitation (BGE) sources are applied simultaneously. With increasing BGE photon energy, a large increase in photocurrent is observed. The external quantum efficiency measurements show that the effect of BGE light is higher with a higher density of tail states present. The extended numerical study by rate equations reproduced the results in a good manner. Furthermore, the simulation results showed that the addition of the BGE light affects the electron occupancy as well as the electron lifetime, which is found to be 0.1 ns in this study.
  IOP Publishing, Scientific journal
  DOI：https://doi.org/10.35848/1347-4065/acd00c
  DOI ID：10.35848/1347-4065/acd00c, ISSN：0021-4922, eISSN：1347-4065
• Significant improvement of injection efficiency in deep-UV LD structures by light Mg doping in p-core layer　　　　　　　　　　　　　　　
  Yuri Itokazu; Noritoshi Maeda; Hiroyuki Yaguchi; Hideki Hirayama
  Japanese Journal of Applied Physics, Apr. 2023, [Reviewed]
  Scientific journal
  DOI：https://doi.org/10.35848/1347-4065/acbda4
  DOI ID：10.35848/1347-4065/acbda4, ORCID：129359119
• Effects of carrier-blocking barrier height on two-step photocurrent generation in dilute nitride intermediate band solar cells
  Shuhei Yagi; Shun Numata; Yasushi Shoji; Yoshitaka Okada; Hiroyuki Yaguchi
  Japanese Journal of Applied Physics, Volume：62, Number：SK, First page：SK1008, Last page：SK1008, Mar. 2023, [Reviewed]
  Abstract
  
  GaAs:N dilute nitride intermediate band solar cells (IBSCs) with different barrier heights for blocking electron transport from the intermediate band (IB) were prepared and the role of such an electron blocking layer (EBL) was investigated. It is found that the EBL effectively confines electrons in the IB states, and the two-step photocurrent generation process is strongly affected by its barrier height. A rate equation analysis well reproduced experimental observations of the applied voltage dependence of the two-step photocurrent generation process. It revealed that the electron extraction both from the conduction band and the IB through the EBL is governed by the thermionic emission process. To meet the requirements of an ideal IBSC, optimized device structures including the barrier height of the EBL have to be designed properly taking into account the material parameters and carrier dynamics under the actual operating condition.
  IOP Publishing, Scientific journal
  DOI：https://doi.org/10.35848/1347-4065/acbf5e
  DOI ID：10.35848/1347-4065/acbf5e, ISSN：0021-4922, eISSN：1347-4065
• Detection of Nonradiative Recombination Centers in GaPN by Combining Two‐Wavelength Excited Photoluminescence and Time‐Resolved Photoluminescence　　　　　　　　　　　　　　　
  Sanjida Ferdous; Hiroki Iwai; Norihiko Kamata; Hiroyuki Yaguchi; Shuhei Yagi
  physica status solidi (b), Volume：258, Number：11, First page：2100119, Last page：2100119, Nov. 2021, [Reviewed]
  Presence and influence of nonradiative recombination (NRR) centers in an intermediate band (IB)-type material, GaP1–xNx ((Formula presented.)), are studied by two-wavelength excited photoluminescence (TWEPL) method and time-resolved photoluminescence (TRPL) measurement at 77 K. With the use of below-gap excitation (BGE) light in addition to an above-gap excitation (AGE), the PL peak intensity is found to increase which indicates the presence of NRR centers and a secondary excitation from the IB to conduction band (CB). Depending on the effect of different BGE energies, an energy diagram on the distribution of NRR centers and NRR process is interpreted. The saturation of PL increase is attributed to the trap-filling effect in NRR centers, which allows us to modify the rate equation. The NRR parameters are evaluated by a qualitative simulation of the modified rate equations of one-level model together with the lifetime determined by TRPL. In continuation of evaluating NRR parameters by rate equation analysis, the addition of TRPL measurement improves accuracy and approaches the determination of NRR parameters. A successful characterization of NRR centers leads to a proper optimization of IB-type solar cells (IBSCs).
  Wiley, English, Scientific journal
  DOI：https://doi.org/10.1002/pssb.202100119
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85114326814&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85114326814&origin=inward
  DOI ID：10.1002/pssb.202100119, ISSN：0370-1972, eISSN：1521-3951, SCOPUS ID：85114326814, Web of Science ID：WOS:000692804600001, 共同研究・競争的資金等ID：24508454
• Insights into Microscopic Crystal Growth Dynamics of CH3NH3PbI3 under a Laser Deposition Process Revealed by In Situ X-ray Diffraction　　　　　　　　　　　　　　　
  Tetsuhiko Miyadera; Yuto Auchi; Kohei Yamamoto; Noboru Ohashi; Tomoyuki Koganezawa; Hiroyuki Yaguchi; Yuji Yoshida; Masayuki Chikamatsu
  ACS APPLIED MATERIALS & INTERFACES, Volume：13, Number：19, First page：22559, Last page：22566, May 2021, [Reviewed]
  The process dynamics for the vacuum deposition of methylammonium lead iodide (MAPbI(3)) perovskite was analyzed by in situ X-ray diffraction using synchrotron radiation. MAPbI(3) was fabricated by alternatingly supplying PbI2 and methylammonium iodide via a laser deposition system installed at the synchrotron beamline BL46XU at SPring-8, and in situ crystallization analysis was conducted. Microscopic insights into the crystallization were obtained, including observation of Laue oscillation during the PbI2 growth and octahedral unit (PbI6) rotation during the transformation into perovskite. On the basis of this analysis, conditions that favor the construction of atomically flat MAPbI3 perovskite films were deduced.
  AMER CHEMICAL SOC, English, Scientific journal
  DOI：https://doi.org/10.1021/acsami.1c04488
  DOI ID：10.1021/acsami.1c04488, ISSN：1944-8244, eISSN：1944-8252, Web of Science ID：WOS:000655027500046
• Solid State Devices and Materials FOREWARD　　　　　　　　　　　　　　　
  Mitsuru Takenaka; Osamu Nakatsuka; Hiroyuki Yaguchi
  JAPANESE JOURNAL OF APPLIED PHYSICS, Volume：60, Number：SB, May 2021
  IOP PUBLISHING LTD, English
  DOI：https://doi.org/10.35848/1347-4065/abef61
  DOI ID：10.35848/1347-4065/abef61, ISSN：0021-4922, eISSN：1347-4065, Web of Science ID：WOS:000635901600001
• Photoluminescence intensity change of GaP1-xNx alloys by laser irradiation　　　　　　　　　　　　　　　
  Md. Zamil Sultan; Akinori Shiroma; Shuhei Yagi; Kengo Takamiya; Hiroyuki Yaguchi
  AIP ADVANCES, Volume：10, Number：9, Sep. 2020, [Reviewed]
  We report the influence of laser irradiation on photoluminescence (PL) intensity to study the evolution of nonradiative recombination centers in GaP1-xNx alloys. PL mapping measurements confirmed that defects to act as nonradiative recombination centers are permanently generated by laser irradiation, which results in irreversible degradation of the PL intensity. Real-time PL measurements revealed that stronger laser irradiation leads to a larger and faster decrease in the PL intensity with irradiation time. The decay of the PL intensity by laser irradiation is larger and faster for a lower nitrogen concentration, indicating that samples with a lower nitrogen concentration are abound with hidden defects to act as nonradiative recombination centers by laser irradiation. It was demonstrated that PL measurement using high-power density photoexcitation is useful to evaluate the generation or multiplication of irradiation-induced nonradiative defects, which causes the deterioration of optoelectronic devices during operation. (c) 2020 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
  AMER INST PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1063/5.0020793
  DOI ID：10.1063/5.0020793, eISSN：2158-3226, ORCID：79669843, Web of Science ID：WOS:000567593300001, 共同研究・競争的資金等ID：24508454
• Epitaxial growth of CH3NH3PbI3 on rubrene single crystal　　　　　　　　　　　　　　　
  Tetsuhiko Miyadera; Yuto Auchi; Tomoyuki Koganezawa; Hiroyuki Yaguchi; Masayuki Chikamatsu
  APL MATERIALS, Volume：8, Number：4, First page：041104, Last page：041104, Apr. 2020, [Reviewed]
  CH3NH3PbI3 perovskite films were grown epitaxially on rubrene single crystals using the laser deposition method for the supply of the source materials (PbI2 and CH3NH3I). An atomically smooth surface with step-and-terrace structures was observed. Several types of crystal orientation were observed, which were dependent on the growth temperature and deposition conditions. For room temperature growth, the crystal orientation was correlated with the orientation of PbI2, which was also found to be grown epitaxially on the rubrene single crystal. In contrast, for growth at elevated temperatures, the crystal orientation with the smallest mismatch between rubrene and perovskite is produced. The construction of atomically ordered ideal perovskite crystals was verified. Moreover, a novel phenomenon was revealed where the octahedral PbI6 unit of PbI2 rotates vertically while retaining its lateral orientation. This growth mechanism results in a layer-by-layer growth and the construction of epitaxial perovskite films with atomic-order flat surfaces.
  AMER INST PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1063/1.5142307
  DOI ID：10.1063/1.5142307, ISSN：2166-532X, ORCID：71441934, Web of Science ID：WOS:000523751500003
• Solid State Devices and Materials FOREWORD　　　　　　　　　　　　　　　
  Hiroyuki Yaguchi; Mitsuru Takenaka; Takuji Hosoi
  JAPANESE JOURNAL OF APPLIED PHYSICS, Volume：59, Apr. 2020
  IOP PUBLISHING LTD, English
  DOI：https://doi.org/10.35848/1347-4065/ab75df
  DOI ID：10.35848/1347-4065/ab75df, ISSN：0021-4922, eISSN：1347-4065, Web of Science ID：WOS:000519630000001
• Enhanced Strain Relaxation in AlGaN Layers Grown on Sputter-Based AlN Templates　　　　　　　　　　　　　　　
  Yosuke Mogami; Atsushi Osawa; Kazuto Ozaki; Yukitake Tanioka; Atsushi Maeoka; Yuri Itokazu; Shunsuke Kuwaba; Masafumi Jo; Noritoshi Maeda; Hiroyuki Yaguchi; Hideki Hirayama
  PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, Volume：257, Number：4, Apr. 2020, [Reviewed]
  Strain plays a crucial role in the performance of ultraviolet (UV) optoelectronic devices. The strain states of AlGaN layers grown on different AlN templates are investigated. Two types of AlN templates are prepared: one is grown solely by metal-organic chemical vapor deposition (MOCVD), and the other is fabricated with the combination of direct current (DC) sputtering, high-temperature annealing, and MOCVD growth. The qualities of 4 mu m-thick MOCVD AlN and 1.2 mu m-thick sputter-based AlN are almost equivalent in terms of dislocation density and surface morphology. However, the strain relaxation ratio of the AlGaN layer is higher for the 1.2 mu m sputter-based AlN than the 4 mu m MOCVD AlN, indicating that the strain state depends on the total thickness of the epilayers on the sapphire substrate. In addition, it is found that the curvature of the sample at room temperature is governed mainly by the thickness of the AlGaN layer. As a result, sputter-based AlN templates allow for the enhanced strain relaxation of the AlGaN layer with a small sample bowing.
  WILEY-V C H VERLAG GMBH, English, Scientific journal
  DOI：https://doi.org/10.1002/pssb.201900590
  DOI ID：10.1002/pssb.201900590, ISSN：0370-1972, eISSN：1521-3951, Web of Science ID：WOS:000508664000001
• Detection of Nonradiative Recombination Centers in GaPN (N:0.105%) by Below-Gap Excitation Light　　　　　　　　　　　　　　　
  Sanjida Ferdous; Norihiko Kamata; Shuhei Yagi; Hiroyuki Yaguchi
  PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, Volume：257, Number：2, Feb. 2020, [Reviewed]
  Investigation on cascade photo-excitation via intermediate band (IB) is promising for improving the efficiency of IB-type solar cells (IBSCs). Increasing nitrogen (N) concentration in GaP changes an ensemble of discrete N-N pair levels to form the IB as well as introducing defect levels acting as nonradiative recombination (NRR) centers. In continuation of detecting NRR centers in GaP1-xNx (x>0.5%), a study is made for the lower N concentration region of 0.105% to understand an original formation of defect levels and their properties. Elimination of temperature quenching by immersing the sample into liquid nitrogen reveals a distribution of NRR centers inside the forbidden energy gap and the shift of Fermi energy depending on above-gap excitation (AGE) density. Profound understanding of IB and defects of GaP1-xNx leads to a proper optimization of IBSCs.
  WILEY-V C H VERLAG GMBH, English, Scientific journal
  DOI：https://doi.org/10.1002/pssb.201900377
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85074068004&origin=inward
  DOI ID：10.1002/pssb.201900377, ISSN：0370-1972, eISSN：1521-3951, ORCID：64953816, SCOPUS ID：85074068004, Web of Science ID：WOS:000489972400001, 共同研究・競争的資金等ID：24508454
• Spectral Change of E- Band Emission in a GaAs:N delta-Doped Superlattice Due to Below-Gap Excitation and Its Discrimination from Thermal Activation　　　　　　　　　　　　　　　
  Md Dulal Haque; Norihiko Kamata; A. Z. M. Touhidul Islam; Shuhei Yagi; Hiroyuki Yaguchi
  JOURNAL OF ELECTRONIC MATERIALS, Volume：49, Number：2, First page：1550, Last page：1556, Feb. 2020, [Reviewed]
  In this study, we examined the E- band luminescence of a GaAs:N delta-doped superlattice (SL) grown by metal organic vapor phase epitaxy with 0.15% nitrogen (N) using two-wavelength excited photoluminescence. It was observed that the photoluminescence (PL) intensity of the low-energy peak (P-2) at 1.38 eV of the E- band was quenched larger compared to the high-energy peak (P-1) at 1.41 eV. This was due to the superposition of below-gap excitation (BGE) light of energy 0.95 eV over the above-gap excitation light of energy 1.45 eV on the SL structure at a fixed temperature of 12 K. On the other hand, at higher temperatures, the PL intensity of the high-energy peak P-1 was quenched higher compared to the low-energy peak P-2 without any addition of the BGE light. We interpreted the experimental results by considering the carrier recombination (CR) model and concluded that the observed PL spectral and intensity change of the E- band emission due to BGE does not result from the thermal activation, but from the optical excitation among the E- band, conduction band, and CR levels in GaAs:N delta-doped structure. We concluded that to achieve high-efficiency intermediate band-type solar cells, it is essential to understand the CR mechanism through CR levels by determining their origin and eliminating them from the material.
  SPRINGER, English, Scientific journal
  DOI：https://doi.org/10.1007/s11664-019-07856-6
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85075954109&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85075954109&origin=inward
  DOI ID：10.1007/s11664-019-07856-6, ISSN：0361-5235, eISSN：1543-186X, ORCID：79739993, SCOPUS ID：85075954109, Web of Science ID：WOS:000500279100002
• Study of nonradiative recombination centers in GaAs:N δ-doped superlattices structures revealed by below-gap excitation light　　　　　　　　　　　　　　　
  Md. Dulal Haque; Norihiko Kamata; A. Z.M. Touhidul Islam; Md. Julkarnain; Shuhei Yagi; Hiroyuki Yaguchi; Yoshitaka Okada
  5th International Conference on Computer, Communication, Chemical, Materials and Electronic Engineering, IC4ME2 2019, Jul. 2019
  Nonradiative recombination (NRR) centers in GaAs:N delta-doped superlattices (SLs) grown by molecular beam epitaxy (MBE) has been investigated by two-wavelength excited photoluminescence (TWEPL) method for conduction band scheme. The PL intensity of E{-} band of the samples with lower nitrogen (N) concentration (0.317% N) initially increases after addition of below-gap excitation (BGE) light over above-gap excitation (AGE) light and then quenches at higher BGE density and energy, while that of GaAs (e-A°) emission of GaAs layers decreases monotonically. For sample with higher N concentration (1.18% N) both the E {-} band and GaAs (e-A°) emission decreases monotonically with enhancing BGE density and degree of decreasing of PL intensity is higher compared to the low N concentration sample. The quenching of PL intensity indicates the existence of NRR centers in GaAs layers and GaAs:N delta-doped SL region. The recombination models have been proposed for explaining the results from the experiments.
  Institute of Electrical and Electronics Engineers Inc., English, International conference proceedings
  DOI：https://doi.org/10.1109/IC4ME247184.2019.9036541
  DOI ID：10.1109/IC4ME247184.2019.9036541, SCOPUS ID：85082984670
• Evolution of morphology and crystalline quality of DC-sputtered AlN films with high-temperature annealing　　　　　　　　　　　　　　　
  Yosuke Mogami; Shogo Motegi; Atsushi Osawa; Kazuto Osaki; Yukitake Tanioka; Atsushi Maeoka; Masafumi Jo; Noritoshi Maeda; Hiroyuki Yaguchi; Hideki Hirayama
  JAPANESE JOURNAL OF APPLIED PHYSICS, Volume：58, Number：SC, Jun. 2019, [Reviewed]
  High-temperature annealing (HTA) is a promising technique to improve the crystalline quality of AlN films. Combining HTA with RF sputtering, Miyake et al. have reported the fabrication of high-quality AlN templates on sapphire [J. Cryst. Growth 456, 155 (2016)], which paves the way to realizing low-cost AlGaN UV optical devices. In terms of AlN growth, DC sputtering is interesting because of its low cost and high throughput. We studied the effect of HTA on the morphology and crystalline quality of DC-sputtered AlN films. As with RF sputtering, HTA substantially improved the crystalline quality of DC-sputtered AlN films. In contrast, hillocks were formed on the surface after HTA, which plausibly stems from the rough surface with spiked structures of the DC-sputtered film. Additional growth of AlN on annealed samples improved the surface morphology and crystalline quality except for the sample containing large hillocks. (C) 2019 The Japan Society of Applied Physics
  IOP PUBLISHING LTD, English, Scientific journal
  DOI：https://doi.org/10.7567/1347-4065/ab1066
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85070748484&origin=inward
  DOI ID：10.7567/1347-4065/ab1066, ISSN：0021-4922, eISSN：1347-4065, ORCID：64953799, SCOPUS ID：85070748484, Web of Science ID：WOS:000474911400036
• Growth temperature dependence of cubic GaN step structures and cubic InN dot arrays grown on MgO (001) vicinal substrates　　　　　　　　　　　　　　　
  Kazumasa Okura; Kengo Takamiya; Shuhei Yagi; Hiroyuki Yaguchi
  JAPANESE JOURNAL OF APPLIED PHYSICS, Volume：58, Number：SC, Jun. 2019, [Reviewed]
  In this paper, we report on the detailed structural features of step-bunched surface formed on cubic (c-) GaN and self-assembled c-InN dot arrays grown on the c-GaN surface, particularly focusing on the growth temperature dependence. Samples were fabricated on MgO (001) vicinal substrates with off-cut angles of 2.0 degrees and 3.5 degrees toward [110] by RF-MBE. Multisteps and terraces with a certain periodicity in the vicinal direction were observed on c-GaN layers. The average terrace width narrowed with lowering the growth temperature and increasing the substrate off-cut angle. The formation of c-InN dots proceeded in the Stranski-Krastanov growth mode with critical thickness of 0.54-0.66 nm. The c-InN dot exhibited a variety of structural features depending on the growth conditions. Positional dot alignment along the multistep edges of the underlayer was observed under some conditions. The degree of alignment was found to be affected by the terrace width on the c-GaN underlayer. (C) 2019 The Japan Society of Applied Physics
  IOP PUBLISHING LTD, English, Scientific journal
  DOI：https://doi.org/10.7567/1347-4065/ab106a
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85070734869&origin=inward
  DOI ID：10.7567/1347-4065/ab106a, ISSN：0021-4922, eISSN：1347-4065, ORCID：64953806, SCOPUS ID：85070734869, Web of Science ID：WOS:000474911400059
• Solid State Devices and Materials　　　　　　　　　　　　　　　
  Takuji Hosoi; Hiroyuki Yaguchi; Hiroyuki Kageshima; Masayuki Chikamatsu; Hirokazu Fujiwara; Mamoru Furuta; Kazuyuki Hirama; Kou Johguchi; Toshiaki Kato; Kenichi Kawaguchi; Akihiko Kikuchi; Kentaro Kinoshita; Hideki Kitada; Masaharu Kobayashi; Rihito Kuroda; Shinichiro Kuroki; Tomoko Matsudai; Takeo Minari; Hiroshi Morioka; Kosuke Nagashio; Kazuyoshi Nakada; Osamu Nakatsuka; Akira Oiwa; Hiroyuki Okada; Takafumi Okuda; Teruo Ono; Toshitsugu Sakamoto; Kenji Shiojima; Mizuki Shirao; Mayumi Takeyama; Tetsu Tanaka; Hirokazu Tatsuoka; Takehiko Tawara; Takeshi Tayagaki; Takashi Tokuda; Kunio Tsuda; Makoto Ueki; Kazuhiko Yamamoto; Wenchang Yeh
  JAPANESE JOURNAL OF APPLIED PHYSICS, Volume：58, Apr. 2019
  IOP PUBLISHING LTD, English
  DOI：https://doi.org/10.7567/1347-4065/ab04f2
  DOI ID：10.7567/1347-4065/ab04f2, ISSN：0021-4922, eISSN：1347-4065, Web of Science ID：WOS:000464309900001
• Photoluminescence characterization of nonradiative recombination centers in MOVPE grown GaAs:N delta-doped superlattice structure　　　　　　　　　　　　　　　
  Md Dulal Haque; Norihiko Kamata; A. Z. M. Touhidul Islam; Zentaro Honda; Shuhei Yagi; Hiroyuki Yaguchi
  OPTICAL MATERIALS, Volume：89, First page：521, Last page：527, Mar. 2019, [Reviewed]
  Nonradiative recombination (NRR) centers in GaAs:N delta-doped superlattice (SL) structure grown by metal organic vapor phase epitaxy (MOVPE) are studied by two-wavelength-excited photoluminescence (PL) method. The PL intensity quenching due to the superposition of below-gap excitation (BGE) light at energies of 0.75, 0.80, 0.92, and 0.95 eV and an above-gap excitation (AGE) light either for the GaAs conduction band (1.69 eV) or E_ band excitation (1.45 eV), respectively indicates the existence of NRR centers inside the GaAs:N delta-doped SL and GaAs layers. The AGE density and BGE density dependence of the PL intensity have been studied for both excitation schemes. Recombination model based on two levels has been proposed to interpret the experimental results and energy distribution of NRR centers inside the GaAs:N delta-doped SLs and GaAs layers. The defect-related parameters are estimated systematically by solving the rate equations and fitting the results with the experimental data that give a phenomenological insight into the sample.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/j.optmat.2019.01.047
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85061552945&origin=inward
  DOI ID：10.1016/j.optmat.2019.01.047, ISSN：0925-3467, eISSN：1873-1252, ORCID：64953761, SCOPUS ID：85061552945, Web of Science ID：WOS:000465509800074
• Epitaxial growth of organolead-halide perovskite on rubrene single crystals　　　　　　　　　　　　　　　
  Y. Auchi; T. Miyadera; T. Koganezawa; H. Yaguchi; M. Chikamatsu; Y. Yoshida
  Extended Abstracts of the 2018 International Conference on Solid State Devices and Materials, Sep. 2018, [Reviewed]
  The Japan Society of Applied Physics, English, International conference proceedings
  DOI：https://doi.org/10.7567/ssdm.2018.f-4-04
  DOI ID：10.7567/ssdm.2018.f-4-04
• Effects of solvent vapor annealing on organic photovoltaics with a new type of solution-processable oligothiophene-based electronic donor material　　　　　　　　　　　　　　　
  Yuki Akiyama; Hiroaki Tachibana; Reiko Azumi; Tetsuhiko Miyadera; Masayuki Chikamatsu; Tomoyuki Koganezawa; Shuhei Yagi; Hiroyuki Yaguchi
  JAPANESE JOURNAL OF APPLIED PHYSICS, Volume：57, Number：8, Aug. 2018, [Reviewed]
  We synthesized a pair of A-D-A-D-A (A = acceptor, D = donor unit) oligomers containing a benzothiadiazole (BT) unit, namely, DRCN5BT-HH and DRCN5BT-TT, which differs in the positions of alkyl side chains. Solution-processed bulk heterojunction solar cells consisting of PC61BM and DRCN5BT-HH gave a high V-oc of 1.10 V and markedly improved power conversion efficiencies up to 3.26% after solvent vapor annealing (SVA). The effects of SVA on the morphology and microstructure of the active layer were investigated by atomic force microscopy (AFM) and grazing-incidence wide angle X-ray scattering (GIWAXS). For DRCN5BT-HH, crystallization, orientation, and molecular ordering were improved, and a fibrillar structure was formed with acicular aggregates of the donor. For DRCN5BT-TT, no marked structural changes were induced by SVA. We found that these morphological and microstructural changes induced by SVA correlate with the differences in the photovoltaic properties of both of the isomers. (C) 2018 The Japan Society of Applied Physics
  IOP PUBLISHING LTD, English, Scientific journal
  DOI：https://doi.org/10.7567/JJAP.57.08RE09
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85050968954&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85050968954&origin=inward
  DOI ID：10.7567/JJAP.57.08RE09, ISSN：0021-4922, eISSN：1347-4065, ORCID：56291723, SCOPUS ID：85050968954, Web of Science ID：WOS:000443891800067
• Biexciton Emission From Single Quantum-Confined Structures in N-Polar (000-1) InGaN/GaN Multiple Quantum Wells　　　　　　　　　　　　　　　
  Kengo Takamiya; Shuhei Yagi; Hiroyuki Yaguchi; Hidefumi Akiyama; Kanako Shojiki; Tomoyuki Tanikawa; Ryuji Katayama
  PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, Volume：255, Number：5, May 2018, [Reviewed]
  We report on the observation of biexciton luminescence from single quantum-confined structures in N-polar InGaN/GaN multiple quantum wells (MQWs) grown on c-plane sapphire by metalorganic vapor phase epitaxy. Sharp emission lines are observed at different positions of the sample by micro-photoluminescence (-PL) mapping. The density of sharp emission lines is approximate to 0.3m(-2), which is comparable with the inversion domain (ID) density found from transmission electron microscope observation, suggesting that the sharp emission lines originate from single quantum-confined structures formed by the combination of quantum well and IDs in N-polar InGaN/GaN MQWs. It is found from the excitation power dependence of the PL intensity of two adjacent sharp lines that the intensity of biexciton luminescence at the lower energy side shows a quadratic dependence on the excitation power while that of exciton luminescence at the higher energy side increased linearly with increasing excitation power. The biexciton binding energy is found to be 0.8meV.
  WILEY-V C H VERLAG GMBH, English, Scientific journal
  DOI：https://doi.org/10.1002/pssb.201700454
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85038872540&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85038872540&origin=inward
  DOI ID：10.1002/pssb.201700454, ISSN：0370-1972, eISSN：1521-3951, ORCID：50444252, SCOPUS ID：85038872540, Web of Science ID：WOS:000432028400019
• Nonradiative recombination centers in GaAs:N delta-doped superlattice revealed by two-wavelength-excited photoluminescence　　　　　　　　　　　　　　　
  Md. Dulal Haque; Norihiko Kamata; Takeshi Fukuda; Zentaro Honda; Shuhei Yagi; Hiroyuki Yaguchi; Yoshitaka Okada
  JOURNAL OF APPLIED PHYSICS, Volume：123, Number：16, Apr. 2018, [Reviewed]
  We use two-wavelength-excited photoluminescence (PL) to investigate nonradiative recombination (NRR) centers in GaAs:N delta-doped superlattice (SL) structures grown by molecular beam epitaxy. The change in photoluminescence (PL) intensity due to the superposition of below-gap excitation at energies of 0.75, 0.80, 0.92, and 0.95 eV and above-gap excitation at energies of 1.69 or 1.45 eV into the GaAs conduction band and the E_ band implies the presence of NRR centers inside the GaAs:N delta-doped SL and/or GaAs layers. The change in PL intensity as a function of the photon number density of below-gap excitation is examined for both bands, which enables us to determine the distribution of NRR centers inside the GaAs:N delta-doped SL and GaAs layers. We propose recombination models to explain the experimental results. Defect-related parameters that give a qualitative insight into the samples are investigated systematically by fitting the rate equations to the experimental data. Published by AIP Publishing.
  AMER INST PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1063/1.5011311
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85045973191&origin=inward
  DOI ID：10.1063/1.5011311, ISSN：0021-8979, eISSN：1089-7550, ORCID：48141847, SCOPUS ID：85045973191, Web of Science ID：WOS:000431147200029
• Growth of InGaAs: N delta-doped superlattices for multi-junction solar cells　　　　　　　　　　　　　　　
  Shumpei Umeda; Shuhei Yagi; Naoya Miyashita; Yoshitaka Okada; Hiroyuki Yaguchi
  2018 IEEE 7TH WORLD CONFERENCE ON PHOTOVOLTAIC ENERGY CONVERSION (WCPEC) (A JOINT CONFERENCE OF 45TH IEEE PVSC, 28TH PVSEC & 34TH EU PVSEC), First page：1861, Last page：1864, 2018, [Reviewed]
  InGaAs:N delta-doped superlattices (SLs) with a band gap of 1 eV were fabricated by molecular beam epitaxy as a candidate for the subcell material of 4-junction lattice-matched tandem solar cells. The N delta-doping was carried out by suppling N source during the growth interruption and the SL structures were obtained by alternate formation of a N delta-doped layer and an In0.06Ga0.94As spacer layer. It was revealed that excess N supply induces interstitial N incorporation and surface roughness. By adjusting the growth conditions and SL structural parameters, coherent growth of SLs with the band gap of 1 eV was successfully achieved.
  IEEE, English, International conference proceedings
  DOI：https://doi.org/10.1109/PVSC.2018.8547315
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85059879947&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85059879947&origin=inward
  DOI ID：10.1109/PVSC.2018.8547315, ISSN：2159-2330, eISSN：2159-2349, SCOPUS ID：85059879947, Web of Science ID：WOS:000469200401194
• Photoluminescence Characterization of Carrier Recombination Centers in 4H-SiC Substrates by Utilizing below Gap Excitation
  Keitaro Kondo; Norihiko Kamata; Hiroyuki Yaguchi; Shuhei Yagi; Takeshi Fukuda; Zentaro Honda
  Materials Science Forum, Volume：897, First page：315, Last page：318, May 2017, [Reviewed]
  Though the crystal growth technology of SiC is improving steadily, it is still crucial to reduce crystalline defects which act as carrier recombination (CR) centers and deteriorate device performance. We detected CR centers in a p-type 4H-SiC substrate by observing the intensity change of photoluminescence due to the addition of a below-gap excitation (BGE) light of 0.93[eV]. We noticed the temperature and the BGE density dependence of band edge (BE) emission in addition to donor acceptor pair (DAP) emission and discriminated the temperature effect from that of BGE. The BGE density dependence of the PL intensity quenching is different among the BE emission, B₀- and C₀-lines of the DAP, respectively. It gives us an important clue for understanding CR mechanisms inside the bandgap of SiC.
  Trans Tech Publications, Scientific journal
  DOI：https://doi.org/10.4028/www.scientific.net/msf.897.315
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85020048562&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85020048562&origin=inward
  DOI ID：10.4028/www.scientific.net/msf.897.315, ISSN：1662-9752, eISSN：1662-9752, ORCID：48141472, SCOPUS ID：85020048562
• Self-organized growth of cubic InN dot arrays on cubic GaN using MgO (001) vicinal substrates　　　　　　　　　　　　　　　
  Kenichi Ishii; Shuhei Yagi; Hiroyuki Yaguchi
  PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS, Volume：254, Number：2, Feb. 2017, [Reviewed]
  Cubic zincblende InN (c-InN) nanoscale dot arrays are grown on cubic GaN (c-GaN) by RF-molecular beam epitaxy using MgO (001) vicinal substrates oriented 3.5 degrees toward [110]. The obtained dot arrays have longer ordering length compared with those grown using conventional on-axis (just) substrates. The c-GaN underlayer grown on the vicinal substrate exhibits a single-domain crystalline structure, while that grown on the just substrate is a mixture of two orthogonal crystalline domains. The change in the c-GaN domain structure leads to the enlarged domain size and lower density of domain boundaries on the c-GaN (001) surface in [1-10]. The longer ordering length of the c-InN dot on the vicinal substrates is reflected by the decrease in the c-GaN domain boundary that disrupts the lateral ordering of the dot arrays. Atomic force microscope image of c-InN dots grown on a single-domain c-GaN. The sample was fabricated using a MgO (001) vicinal substrate.
  WILEY-V C H VERLAG GMBH, English, Scientific journal
  DOI：https://doi.org/10.1002/pssb.201600542
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85000938311&origin=inward
  DOI ID：10.1002/pssb.201600542, ISSN：0370-1972, eISSN：1521-3951, ORCID：48141861, SCOPUS ID：85000938311, Web of Science ID：WOS:000394614300028
• Spectral change of intermediate band luminescence in GaP:N due to below-gap excitation: Discrimination from thermal activation　　　　　　　　　　　　　　　
  Kamata, N.; Suetsugu, M.; Haque, D.; Yagi, S.; Yaguchi, H.; Karlsson, F.; Holtz, P.O.
  Physica Status Solidi (B) Basic Research, Volume：254, Number：2, 2017, [Reviewed]
  © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim As an intermediate band (IB) originating from discrete nitrogen (N) levels is formed in GaP:N with increasing N concentration, GaP1−xNx alloy is considered to be a promising candidate for IB-type solar cells. We studied the IB luminescence of a GaP1−xNx with 0.56% N and detected carrier recombination (CR) levels by superposing a below-gap excitation (BGE) light of 1.17 eV. We resolved a high-energy component of 2.15 eV in the IB luminescence, Ihigh, from total luminescence intensity Iall. With increasing the BGE density at fixed temperature of 5 K, the amount of decrease in Ihigh was distinctly smaller than that of simple temperature rise without the BGE at the same Iall value. We conclude that the observed intensity change of the IB luminescence due to the BGE comes not from thermal activation, but from optical excitation among the IB, conduction band, and CR levels in GaP1−xNx. It is of primal importance to understand CR levels toward determining their origins and eliminating them for realization of efficient IB-type solar cells.
  WILEY-V C H VERLAG GMBH, English, Scientific journal
  DOI：https://doi.org/10.1002/pssb.201600566
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85003749566&origin=inward
  DOI ID：10.1002/pssb.201600566, ISSN：0370-1972, eISSN：1521-3951, ORCID：48141829, SCOPUS ID：85003749566, Web of Science ID：WOS:000394614300035
• Growth of InN/GaN dots on 4H-SiC(0001) 4° off vicinal substrates by molecular beam epitaxy　　　　　　　　　　　　　　　
  Shuhei Yagi; Hiroyuki Yaguchi; Keisuke Matsuoka
  Journal of Crystal Growth, Volume：477, First page：201, Last page：206, 2017, [Reviewed]
  We have fabricated self-assembled InN dots on GaN using 4H-SiC(0001) vicinal substrates (4 degrees off toward [11-20]). The size and density of InN dots were well controlled by changing the deposition amount and the growth temperature of InN. Atomic force microscope (AFM) observation revealed that the critical thickness of InN for 2D-3D transition was between 0.8 and 1.0 nm. In addition, it was found that the InN dots were preferentially formed at the multistep edges on GaN. Therefore, the preparation of periodic multistep structures on GaN is considered to be an effective way to obtain highly ordered self-assembled InN dot arrays. (C) 2017 Elsevier B.V. All rights reserved.
  Elsevier {BV}, English, Scientific journal
  DOI：https://doi.org/10.1016/J.JCRYSGRO.2017.05.021
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85020105871&origin=inward
  DOI ID：10.1016/J.JCRYSGRO.2017.05.021, ISSN：0022-0248, eISSN：1873-5002, ORCID：56291782, SCOPUS ID：85020105871, Web of Science ID：WOS:000413646100043
• Self-Organized Growth of Cubic InN Dot Arrays on MgO (001) Vicinal Substrates　　　　　　　　　　　　　　　
  Kenichi Ishii; Shuhei Yagi; Hiroyuki Yaguchi
  2016 COMPOUND SEMICONDUCTOR WEEK (CSW) INCLUDES 28TH INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE & RELATED MATERIALS (IPRM) & 43RD INTERNATIONAL SYMPOSIUM ON COMPOUND SEMICONDUCTORS (ISCS), 2016, [Reviewed]
  IEEE, English, International conference proceedings
  DOI：https://doi.org/10.1109/ICIPRM.2016.7528673
  DOI ID：10.1109/ICIPRM.2016.7528673, ORCID：56291759, Web of Science ID：WOS:000392285400156
• Optical Characterization of Carrier Recombination Processes in GaPN by Two-Wavelength Excited Photoluminescence　　　　　　　　　　　　　　　
  Makiko Suetsugu; Norihiko Kamata; Shuhei Yagi; Hiroyuki Yaguchi; Takeshi Fukuda; Fredrik Karlsson; Per-Olof Holts
  2016 COMPOUND SEMICONDUCTOR WEEK (CSW) INCLUDES 28TH INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE & RELATED MATERIALS (IPRM) & 43RD INTERNATIONAL SYMPOSIUM ON COMPOUND SEMICONDUCTORS (ISCS), 2016, [Reviewed]
  IEEE, English, International conference proceedings
  DOI：https://doi.org/10.1109/ICIPRM.2016.7528672
  DOI ID：10.1109/ICIPRM.2016.7528672, ORCID：56291722, Web of Science ID：WOS:000392285400155
• Two-Wavelength Excited Photoluminescence in 4H-SiC Substrate -Dependence on BGE Power Density-　　　　　　　　　　　　　　　
  Keitaro Kondo; Norihiko Kamata; Shuhei Yagi; Hiroyuki Yaguchi; Takeshi Fukuda; Zentaro Honda
  2016 COMPOUND SEMICONDUCTOR WEEK (CSW) INCLUDES 28TH INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE & RELATED MATERIALS (IPRM) & 43RD INTERNATIONAL SYMPOSIUM ON COMPOUND SEMICONDUCTORS (ISCS), 2016, [Reviewed]
  IEEE, English, International conference proceedings
  DOI：https://doi.org/10.1109/ICIPRM.2016.7528594
  DOI ID：10.1109/ICIPRM.2016.7528594, ORCID：56291772, Web of Science ID：WOS:000392285400077
• Molecular beam epitaxial growth of intermediate-band materials based on GaAs: N delta-doped superlattices　　　　　　　　　　　　　　　
  Tomoya Suzuki; Kazuki Osada; Shuhei Yagi; Shunya Naitoh; Yasushi Shoji; Yasuto Hijikata; Yoshitaka Okada; Hiroyuki Yaguchi
  JAPANESE JOURNAL OF APPLIED PHYSICS, Volume：54, Number：8, First page：08KA07, Aug. 2015, [Reviewed]
  We fabricated GaAs: N delta-doped superlattices (SLs) by molecular beam epitaxy and investigated their potential as an intermediate-band photoabsorber in high-efficiency solar cells. The N area concentration in a N delta-doped layer was well controlled by adjusting the fabrication conditions, and the SLs with the average N composition of up to 1.5% were obtained. The SL minibands related to the N-induced E+ and E- conduction subbands were formed with well-separated bottom energies of up to 0.4 eV, indicating the suitability of this material system for use in intermediate-band solar cells. A two-step photoabsorption process in a solar cell with the SL absorber was successfully demonstrated through external quantum efficiency measurements under additional infrared illumination at room temperature. (C) 2015 The Japan Society of Applied Physics
  IOP PUBLISHING LTD, English, Scientific journal
  DOI：https://doi.org/10.7567/JJAP.54.08KA07
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84938504709&origin=inward
  DOI ID：10.7567/JJAP.54.08KA07, ISSN：0021-4922, eISSN：1347-4065, ORCID：64953767, SCOPUS ID：84938504709, Web of Science ID：WOS:000358662900008
• Control of intermediate-band configuration in GaAs: N delta-doped superlattice　　　　　　　　　　　　　　　
  Kazuki Osada; Tomoya Suzuki; Shuhei Yagi; Shunya Naitoh; Yasushi Shoji; Yasuto Hijikata; Yoshitaka Okada; Hiroyuki Yaguchi
  JAPANESE JOURNAL OF APPLIED PHYSICS, Volume：54, Number：8, First page：08KA04, Aug. 2015, [Reviewed]
  GaAs: N delta-doped superlattices (SLs) consisting of alternating layers of undoped and N delta-doped GaAs were fabricated by molecular beam epitaxy (MBE) as possible candidates for the light-absorbing material of intermediate-band solar cells (IBSCs). Since the energy gaps in IBSCs need to be adjusted to optimum values to achieve sufficiently high conversion efficiency, it is important to control precisely the band configuration of intermediate-band (IB) materials. In this study, we demonstrated the control of the IB energy configuration in GaAs: N delta-doped SLs by changing their structural parameters. Optical transitions due to the SL minibands related to the N-induced conduction subbands E+ and E- were clearly observed and the transition energies depended systematically on the N area density and period length of the SLs. Conversion efficiency calculations based on the detailed balance model indicated that IBSCs with an efficiency of nearly 60% are achievable by using the fabricated GaAs: N delta-doped SLs. (C) 2015 The Japan Society of Applied Physics
  IOP PUBLISHING LTD, English, Scientific journal
  DOI：https://doi.org/10.7567/JJAP.54.08KA04
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84938516127&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84938516127&origin=inward
  DOI ID：10.7567/JJAP.54.08KA04, ISSN：0021-4922, eISSN：1347-4065, ORCID：56291671, SCOPUS ID：84938516127, Web of Science ID：WOS:000358662900005
• Growth temperature dependence of the surface segregation of Er atoms in GaAs during molecular beam epitaxy　　　　　　　　　　　　　　　
  Ri Guo Jin; Shuhei Yagi; Yasuto Hijikata; Hiroyuki Yaguchi
  JAPANESE JOURNAL OF APPLIED PHYSICS, Volume：54, Number：5, First page：051201, May 2015, [Reviewed]
  We have quantitatively studied the temperature dependence of the surface segregation of Er atoms in GaAs during molecular beam epitaxy using secondary ion mass spectroscopy. It was found that a significant number of Er atoms segregate to the growing surface at temperatures of 400 degrees C and above and that the segregation decay length is approximately 0.5 mu m at 500 degrees C, indicating that the incorporation ratio of Er atoms into GaAs is less than 10(-3). In contrast to the growth at higher temperatures, GaAs overlayer growth at a temperature as low as 300 degrees C is effective in suppressing the surface segregation of Er and obtaining delta-doped structures. (C) 2015 The Japan Society of Applied Physics
  IOP PUBLISHING LTD, English, Scientific journal
  DOI：https://doi.org/10.7567/JJAP.54.051201
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84983072013&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84983072013&origin=inward
  DOI ID：10.7567/JJAP.54.051201, ISSN：0021-4922, eISSN：1347-4065, ORCID：56291658, SCOPUS ID：84983072013, Web of Science ID：WOS:000354980300009, 共同研究・競争的資金等ID：11611368
• Differences in SiC thermal oxidation process between crystalline surface orientations observed by in-situ spectroscopic ellipsometry　　　　　　　　　　　　　　　
  Daisuke Goto; Yasuto Hijikata; Shuhei Yagi; Hiroyuki Yaguchi
  JOURNAL OF APPLIED PHYSICS, Volume：117, Number：9, First page：095306, Mar. 2015, [Reviewed]
  For a better understanding of the SiC oxidation mechanism, we investigated differences in the oxidation process for surfaces with different crystal orientations. Real-time observations of oxidation processes for (0001) Si-face, (11 (2) over bar0) a-face, and (000 (1) over bar) C-face substrates at various oxidation temperatures were performed using in-situ spectroscopic ellipsometry. Massoud's empirical equation, which is composed of the classical Deal-Grove equation added by an exponential term, was applied to the observed growth rates and the oxidation rate parameters were extracted by curve fitting. The SiC oxidation mechanism is discussed in terms of the oxidation temperature dependence and surface orientation dependence of the oxidation rate parameters. (C) 2015 AIP Publishing LLC.
  AMER INST PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1063/1.4914050
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84924310120&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84924310120&origin=inward
  DOI ID：10.1063/1.4914050, ISSN：0021-8979, eISSN：1089-7550, ORCID：56291706, SCOPUS ID：84924310120, Web of Science ID：WOS:000351134400041
• Photoluminescence Study of Oxidation-Induced Stacking Faults in 4H-SiC Epilayers
  Miyano, Y; Yagi, S; Hijikata, Y; Yaguchi, H
  Materials Science Forum, Volume：821-823, First page：327, Last page：330, 2015, [Reviewed]
  Trans Tech Publications, Scientific journal
  DOI：https://doi.org/10.4028/www.scientific.net/MSF.821-823.327
  DOI ID：10.4028/www.scientific.net/MSF.821-823.327, ISSN：1662-9752, ORCID：50444258
• Surface orientation dependence of SiC oxidation process studied by in-situ spectroscopic ellipsometry　　　　　　　　　　　　　　　
  Goto, D.; Yagi, S.; Hijikata, Y.; Yaguchi, H.
  Materials Science Forum, Volume：821-823, First page：371, Last page：374, 2015, [Reviewed]
  © (2014) Trans Tech Publications, Switzerland. We performed real-time observations of SiC oxidation at various temperatures by in-situ spectroscopic ellipsometry using a Si-face, an a-face and a C-face substrates. We calculated oxide growth rates based on “Si-C emission model,” taking into account the emission of interfacial Si and C atoms from the SiC–SiO2 interface. The calculated values well reproduced the oxide thickness dependence of oxide growth rates. We discussed the SiC oxidation mechanism using the parameters deduced from the calculations.
  Materials Science Forum, Scientific journal
  DOI：https://doi.org/10.4028/www.scientific.net/MSF.821-823.371
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84950341587&origin=inward
  DOI ID：10.4028/www.scientific.net/MSF.821-823.371, ISSN：0255-5476, eISSN：1662-9752, ORCID：64953813, SCOPUS ID：84950341587
• Microstructures of InN film on 4H-SiC (0001) substrate grown by RF-MBE　　　　　　　　　　　　　　　
  P. Limsuwan; H. Yaguchi; M. Orihara; S. Sanorpim; P. Jantawongrit
  Journal of Semiconductors, Volume：36, Number：8, 2015, [Reviewed]
  © 2015 Chinese Institute of Electronics. InN film was grown on 4H-SiC (0001) substrate by RF plasma-assisted molecular beam epitaxy (RF-MBE). Prior to the growth of InN film, an InN buffer layer with a thickness of ∼5.5 nm was grown on the substrate. Surface morphology, microstructure and structural quality of InN film were investigated. Micro-structural defects, such as stacking faults and anti-phase domain in InN film were carefully investigated using transmission electron microscopy (TEM). The results show that a high density of line contrasts, parallel to the growth direction (c-axis), was clearly observed in the grown InN film. Dark field TEM images recorded with diffraction vectors and g = 0002 revealed that such line contrasts evolved from a coalescence of the adjacent misoriented islands during the initial stage of the InN nucleation on the substrate surface. This InN nucleation also led to a generation of anti-phase domains.
  IOP PUBLISHING LTD, English, Scientific journal
  DOI：https://doi.org/10.1088/1674-4926/36/8/083002
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84940094786&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84940094786&origin=inward
  DOI ID：10.1088/1674-4926/36/8/083002, ISSN：1674-4926, ORCID：56291719, SCOPUS ID：84940094786, Web of Science ID：WOS:000218443900007
• Photoluminescence study of oxidation-induced faults in 4H-SiC epilayers　　　　　　　　　　　　　　　
  Miyano, Y.; Asafuji, R.; Yagi, S.; Hijikata, Y.; Yaguchi, H.
  AIP Advances, Volume：5, Number：12, First page：127116, 2015, [Reviewed]
  We investigated the effect of thermal oxidation on crystalline faults in 4H-SiC epilayers using photoluminescence imaging. We found that a comb-shaped dislocation array was deformed by thermal oxidation. We also found that line-shaped faults perpendicular to the off-cut direction were formed during oxidation and were stretched and increased with the oxidation time. Since these line-shaped faults were peculiar to the oxidation and stretched/increased with the oxide growth, they were identified as oxidation-induced stacking faults as seen in Si oxidation. (C) 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.
  AMER INST PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1063/1.4938126
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84952672264&origin=inward
  DOI ID：10.1063/1.4938126, ISSN：2158-3226, eISSN：2158-3226, ORCID：64953793, SCOPUS ID：84952672264, Web of Science ID：WOS:000367596300016
• Enhanced optical absorption due to E+-related band transition in GaAs:N delta-doped superlattices　　　　　　　　　　　　　　　
  Shuhei Yagi; Shunsuke Noguchi; Yasuto Hijikata; Shigeyuki Kuboya; Kentaro Onabe; Yoshitaka Okada; Hiroyuki Yaguchi
  APPLIED PHYSICS EXPRESS, Volume：7, Number：10, Oct. 2014, [Reviewed]
  The photoabsorption characteristics of GaAs:N delta-doped superlattices (SLs) are investigated. Periodic insertion of N delta-doped induces the formation of conduction subbands E+ and E-, and each conduction subband forms SL minibands with the GaAs between the delta-doped layers. In addition to an optical absorption related to the E- band, an abrupt absorption edge originating transition between the valence band and an E+-related miniband is observed at 1.6 eV in a photoluminescence excitation indicating that GaAs:N delta-doped SLs are promising candidates for the absorber of intermediate-band solar cells. (C) 2014 The Japan Society of Applied Physics
  IOP PUBLISHING LTD, English, Scientific journal
  DOI：https://doi.org/10.7567/APEX.7.102301
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84988891884&origin=inward
  DOI ID：10.7567/APEX.7.102301, ISSN：1882-0778, eISSN：1882-0786, ORCID：48141835, SCOPUS ID：84988891884, Web of Science ID：WOS:000344439300007
• Photoreflectance study of the temperature dependence of excitonic transitions in dilute GaAsN alloys　　　　　　　　　　　　　　　
  Wataru Okubo; Shuhei Yagi; Yasuto Hijikata; Kentaro Onabe; Hiroyuki Yaguchi
  PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, Volume：211, Number：4, First page：752, Last page：755, Apr. 2014, [Reviewed]
  We have studied the temperature dependence of optical transitions in dilute GaAsN alloys using photoreflectance (PR). A delocalized-state transition is clearly observed in PR spectra while several localized-state emission lines due to isoelectronic centers appear in photoluminescence spectra. The energy of optical transitions observed in PR spectra is in agreement with the excitonic transition energy in photoluminescence excitation spectra, clearly showing that the optical transitions in PR spectra are excitonic transitions. We analyzed the temperature dependence of the excitonic transition energies using the Bose-Einstein statistical expression, and found that even dilute alloys follow the same trend as GaAsN alloys with higher nitrogen concentrations. We discuss the coexistence of localized and delocalized states in dilute GaAsN alloys in terms of the random distribution of N atoms.
  WILEY-V C H VERLAG GMBH, English, Scientific journal
  DOI：https://doi.org/10.1002/pssa.201300462
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84897986009&origin=inward
  DOI ID：10.1002/pssa.201300462, ISSN：1862-6300, eISSN：1862-6319, ORCID：56291616, SCOPUS ID：84897986009, Web of Science ID：WOS:000333911800006, 共同研究・競争的資金等ID：11611368
• Si emission into the oxide layer during oxidation of silicon carbide　　　　　　　　　　　　　　　
  Yurie Akasaka; Yasuto Hijikata; Shuhei Yagi; HIROYUKI YAGUCHI
  Materials Science Forum, Volume：778-780, First page：553, Last page：556, 2014, [Reviewed]
  Trans Tech Publications, Scientific journal
  DOI：https://doi.org/10.4028/WWW.SCIENTIFIC.NET/MSF.778-780.553
  DOI ID：10.4028/WWW.SCIENTIFIC.NET/MSF.778-780.553, ISSN：1662-9752, ORCID：56291610, Web of Science ID：WOS:000336634100130
• First-principles study on the conduction band electron states of GaAsN alloys　　　　　　　　　　　　　　　
  Kei Sakamoto; Hiroyuki Yaguchi
  PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 11, NO 3-4, Volume：11, Number：3-4, First page：911, Last page：913, 2014, [Reviewed]
  We have analyzed the electronic states of the lowest conduction band of GaAsN alloys based on the first-principles calculation. In order to study the nitrogen concentration dependence of the electron effective mass, we calculated the electronic structure of GaAsN alloys using a full-potential density functional theory program. The calculated effective mass of GaAsN with a dilute nitrogen concentration is about twice as heavy as that of GaAs. In addition, the effective mass is found to decrease with increasing nitrogen concentration although it is always heavier than that of GaAs. In addition, we calculated the density of states of GaAsN to examine what the cause of the decrease in the effective mass is. Our calculations suggest the discontinuity of the physical property from GaAs to GaAsN and provide an important insight into the formation of the conduction band states of GaAsN alloys. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  WILEY-V C H VERLAG GMBH, English, International conference proceedings
  DOI：https://doi.org/10.1002/pssc.201300531
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84898548200&origin=inward
  DOI ID：10.1002/pssc.201300531, ISSN：1862-6351, eISSN：1610-1642, ORCID：64953783, SCOPUS ID：84898548200, Web of Science ID：WOS:000346071300134, 共同研究・競争的資金等ID：11611368
• Conversion Efficiency of Intermediate Band Solar Cells with GaAs:N delta-Doped Superlattices　　　　　　　　　　　　　　　
  Shuhei Yagi; Shunsuke Noguchi; Yasuto Hijikata; Shigeyuki Kuboya; Kentaro Onabe; Hiroyuki Yaguchi
  JAPANESE JOURNAL OF APPLIED PHYSICS, Volume：52, Number：10, Oct. 2013, [Reviewed]
  The performance of intermediate band solar cells using a GaAs:N delta-doped superlattice (SL) as the optical absorber is analyzed. In GaAs: N delta-doped SLs, both of the E+ and E- bands formed around the N delta-doped layers form SL potentials with the conduction band of the spacer GaAs layers, resulting in the formation of multiple minibands. The conversion efficiency limits of the solar cells are calculated using the detailed balance model based on intermediate band structures composed of the valence band and two minibands formed respectively in the E-- and E+-related SL potentials. A high efficiency of 62.6% for full concentration is expected by properly adjusting the structural parameters of the SL. Alloying other elements such as In to a GaAs:N delta-doped SL is a possible way to further facilitate the development of intermediate band materials for high-efficiency solar cells. (C) 2013 The Japan Society of Applied Physics
  IOP PUBLISHING LTD, English, Scientific journal
  DOI：https://doi.org/10.7567/JJAP.52.102302
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84887232116&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84887232116&origin=inward
  DOI ID：10.7567/JJAP.52.102302, ISSN：0021-4922, eISSN：1347-4065, ORCID：30384763, SCOPUS ID：84887232116, Web of Science ID：WOS:000325209000024
• Analysis of Electronic Structures of Nitrogen delta-Doped GaAs Superlattices for High Efficiency Intermediate Band Solar Cells　　　　　　　　　　　　　　　
  Shunsuke Noguchi; Shuhei Yagi; Daisuke Sato; Yasuto Hijikata; Kentaro Onabe; Shigeyuki Kuboya; Hiroyuki Yaguchi
  IEEE JOURNAL OF PHOTOVOLTAICS, Volume：3, Number：4, First page：1287, Last page：1291, Oct. 2013, [Reviewed]
  Nitrogen delta-doped GaAs superlattices (SLs) were fabricated, and their energy structures were investigated. A number of strong transition signals are observed in photoreflectane (PR) spectra in an energy range from 1.54 to 1.78 eV for SL samples in which any transitions are not observed in uniformly nitrogen-doped GaAsN with comparable nitrogen content. Both of the E+ and E- bands formed around the nitrogen delta-doped layers compose SL potentials with the conduction band of the spacer GaAs layers, resulting in the formation of multiple minibands. The energy range of the SL minibands well explains the observed transition energies in the PR spectra. The PR signal intensity ratios of the E+-related transitions to the E--related transitions for the SLs are notably large compared with those usually observed for conventional GaAsN alloys. This enhancement of electron transition associated with the E+-related bands should be advantageous as intermediate band material. Therefore, nitrogen delta-doped GaAs SLs are expected to be an excellent alternative to uniformly doped GaAsN alloys for the use in intermediate band solar cells.
  IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, English, Scientific journal
  DOI：https://doi.org/10.1109/JPHOTOV.2013.2271978
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84884672481&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84884672481&origin=inward
  DOI ID：10.1109/JPHOTOV.2013.2271978, ISSN：2156-3381, eISSN：2156-3403, ORCID：30384761, SCOPUS ID：84884672481, Web of Science ID：WOS:000324881400023
• Direct Evidence of Carrier Excitation from Intermediate Band States in GaPN by Two-Wavelength Excited Photoluminescence　　　　　　　　　　　　　　　
  Abu Zafor Muhammad Touhidul Islam; Tsukasa Hanaoka; Kentaro Onabe; Shuhei Yagi; Norihiko Kamata; Hiroyuki Yaguchi
  APPLIED PHYSICS EXPRESS, Volume：6, Number：9, Sep. 2013, [Reviewed]
  An investigation of two-wavelength excited photoluminescence on GaPN alloys containing 0.56% nitrogen was conducted to directly excite intermediate band (IB) states and monitor its impact on photoluminescence (PL) properties. The 22 K PL due to above-gap excitation (AGE) showed broad peak emission induced by the IB states. With the use of below-gap excitation (BGE) of 1.17 eV energy in addition to the AGE, the PL peak intensity was found to decrease linearly with increasing the BGE power, which suggests that the BGE perturbs the bound exciton recombination mechanism by exciting electrons from the IB states through the dissociation of excitons. (c) 2013 The Japan Society of Applied Physics
  IOP PUBLISHING LTD, English, Scientific journal
  DOI：https://doi.org/10.7567/APEX.6.092401
  DOI ID：10.7567/APEX.6.092401, ISSN：1882-0778, eISSN：1882-0786, Web of Science ID：WOS:000324494100020
• RF-MBE growth of cubic InN nano-scale dots on cubic GaN　　　　　　　　　　　　　　　
  Junichiro Suzuki; Misao Orihara; Shuhei Yagi; Yasuto Hijikata; Hiroyuki Yaguchi
  JOURNAL OF CRYSTAL GROWTH, Volume：378, First page：454, Last page：458, Sep. 2013, [Reviewed]
  This paper reports the first successful growth and structural control of cubic InN (c-InN) nano-scale dots. The samples were grown on MgO (0 0 1) substrates by RF-N-2 plasma molecular beam epitaxy (RF-MBE). Cubic GaN (c-GaN) underlayers with a thickness of 500 nm were grown on the substrates followed by the growth of a few nm-thick InN under various conditions. The formation of InN dots aligned along the < 1 1 0 > directions were confirmed by atomic force microscopy (AFM). X-ray diffraction (XRD) measurements suggested the cubic zincblende lattice structure of the obtained InN dots. The area density and size of c-InN dots were well controlled by adjusting the growth conditions such as the substrate temperature and the In flux, and a very high dot density of 2.2 x 10(11) cm(-2) was successfully obtained at a growth temperature of 470 degrees C and an In flux of 7.0 x 10(-5) Pa. (c) 2013 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/j.jcrysgro.2012.12.050
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84885434999&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84885434999&origin=inward
  DOI ID：10.1016/j.jcrysgro.2012.12.050, ISSN：0022-0248, eISSN：1873-5002, ORCID：30384771, SCOPUS ID：84885434999, Web of Science ID：WOS:000323355900113
• Molecular beam epitaxy of ErGaAs alloys on GaAs (001) substrates　　　　　　　　　　　　　　　
  Ri Guo Jin; Shuhei Yagi; Yasuto Hijikata; Shigeyuki Kuboya; Kentaro Onabe; Ryuji Katayama; Hiroyuki Yaguchi
  JOURNAL OF CRYSTAL GROWTH, Volume：378, First page：85, Last page：87, Sep. 2013, [Reviewed]
  We have successfully grown high crystalline quality ErGaAs alloy layers by solid-source molecular beam epitaxy. The X-ray diffraction (XRD) peak of ErGaAs alloys was found to shift systematically from the GaAs peak with increasing Er concentration up to 3.7%. XRD (1 1 5) reciprocal space map measurements revealed that the ErGaAs epitaxial layer is coherently grown on GaAs. We found from XRD results that ErGaAs alloys with low Er concentrations tend to crystallize in the zincblende structure. (c) 2012 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/j.jcrysgro.2012.12.043
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84885427998&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84885427998&origin=inward
  DOI ID：10.1016/j.jcrysgro.2012.12.043, ISSN：0022-0248, ORCID：30384766, SCOPUS ID：84885427998, Web of Science ID：WOS:000323355900023
• Direct evidence of carrier excitation from intermediate band states in GaPN by two-wavelength excited photoluminescence　　　　　　　　　　　　　　　
  Abu Zafor Muhammad Touhidul Islam; Tsukasa Hanaoka; Kentaro Onabe; Shuhei Yagi; Norihiko Kamata; Hiroyuki Yaguchi
  Applied Physics Express, Volume：6, Number：9, First page：3, Sep. 2013, [Reviewed]
  An investigation of two-wavelength excited photoluminescence on GaPN alloys containing 0.56% nitrogen was conducted to directly excite intermediate band (IB) states and monitor its impact on photoluminescence (PL) properties. The 22 K PL due to above-gap excitation (AGE) showed broad peak emission induced by the IB states. With the use of below-gap excitation (BGE) of 1.17 eV energy in addition to the AGE, the PL peak intensity was found to decrease linearly with increasing the BGE power, which suggests that the BGE perturbs the bound exciton recombination mechanism by exciting electrons from the IB states through the dissociation of excitons. © 2013 The Japan Society of Applied Physics.
  IOP PUBLISHING LTD, English, Scientific journal
  DOI：https://doi.org/10.7567/APEX.6.092401
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84883664354&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84883664354&origin=inward
  DOI ID：10.7567/APEX.6.092401, ISSN：1882-0778, eISSN：1882-0786, ORCID：30384764, SCOPUS ID：84883664354, Web of Science ID：WOS:000324494100020
• Observation of optical spin injection into Ge-based structures at room temperature　　　　　　　　　　　　　　　
  Yuhsuke Yasutake; Shuhei Hayashi; Hiroyuki Yaguchi; Susumu Fukatsu
  APPLIED PHYSICS LETTERS, Volume：102, Number：24, Jun. 2013, [Reviewed]
  Non-zero spin polarization induced by optical orientation was clearly observed at room temperature in a Ge/Ge0.8Si0.2 quantum well grown on Ge and a Ge layer grown on Si by molecular beam epitaxy, whereas it was absent in bulk Ge. This occurred because indirect-gap photoluminescence (PL), which can obscure the spin-polarization information carried by the direct-gap PL, was quenched by unintentional growth-related defects in the epitaxial layers. Such interpretation was confirmed by applying time gating that effectively removed the indirect-gap PL characterized by a slower rise time, which allowed us to demonstrate the existence of room-temperature spin polarization in bulk Ge. (C) 2013 AIP Publishing LLC.
  AMER INST PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1063/1.4811495
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84879811389&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84879811389&origin=inward
  DOI ID：10.1063/1.4811495, ISSN：0003-6951, ORCID：30384767, SCOPUS ID：84879811389, Web of Science ID：WOS:000320962400045
• Optical properties and carrier dynamics in asymmetric coupled ingan multiple quantum wells　　　　　　　　　　　　　　　
  Guo En Weng; Bao Ping Zhang; Ming Ming Liang; Xue Qin Lv; Jiang Yong Zhang; Lei Ying Ying; Zhi Ren Qiu; H. Yaguchi; S. Kuboya; K. Onabe; Shao Qiang Chen; H. Akiyama
  Functional Materials Letters, Volume：6, Number：2, First page：5, Apr. 2013, [Reviewed]
  Optical properties and carrier dynamics of InGaN/GaN asymmetric coupled quantum wells (ACQWs) are studied by excitation-power-dependent photoluminescence (PL), photoreflectance (PR) and time-resolved PL (TRPL) experiments. Under weak excitations, only the emission from the widest well is observed due to the tunneling from narrower to wider wells. Under strong excitations, the carrier distribution becomes more uniform and an enhanced emission from the mid well (2.5 nm well) is observed. Dependence of the PL intensity on excitation power is well explained by a rate equation model. The energy levels in the ACQW structure are clearly revealed by PR measurements and are in good agreement with calculations. Our results indicate that the enhanced emission from the mid well is ascribed to «reverse tunneling» from 3.0 to 2.5 nm well, which is confirmed by TRPL experiments. © 2013 World Scientific Publishing Company.
  WORLD SCIENTIFIC PUBL CO PTE LTD, English, Scientific journal
  DOI：https://doi.org/10.1142/S1793604713500215
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84876756647&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84876756647&origin=inward
  DOI ID：10.1142/S1793604713500215, ISSN：1793-6047, eISSN：1793-7213, ORCID：30384769, SCOPUS ID：84876756647, Web of Science ID：WOS:000319747700012
• Stacked structure of self-organized cubic InN nano-dots grown by molecular beam epitaxy　　　　　　　　　　　　　　　
  Shuhei Yagi; Junichiro Suzuki; Misao Orihara; Yasuto Hijikata; Hiroyuki Yaguchi
  PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 10, NO 11, Volume：10, Number：11, First page：1545, Last page：1548, 2013, [Reviewed]
  A two-stacked cubic (c-) InN/c-GaN nano-scale dot structure is fabricated on a MgO(001) substrate by RF-N-2 molecular beam epitaxy and its microstructures are investigated by scanning transmission electron microscopy (STEM). The cubic lattice structure of InN dots is verified by STEM observations. It is implied that c-InN dots formed on a smooth c-GaN surface have the {111} facets. The c-GaN cap layer has an uneven surface, which reflects the shape of the c-InN dots embedded beneath the cap layer. InN selectively deposits in concave regions on the c-GaN cap layer, which appear above in-between positions of embedded dots. Thus, stacked c-InN/c-GaN dots do not tend to align vertically. These results open the possibility for multi-stacking structures of c-InN dots and their application to high-performance optoelectronic devices based on the nitride semiconductors. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  WILEY-V C H VERLAG GMBH, English, International conference proceedings
  DOI：https://doi.org/10.1002/pssc.201300275
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84887619549&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84887619549&origin=inward
  DOI ID：10.1002/pssc.201300275, ISSN：1862-6351, eISSN：1610-1642, ORCID：30384772, SCOPUS ID：84887619549, Web of Science ID：WOS:000334583400049
• RF-MBE growth of cubic AlN on MgO (001) substrates via 2-step c-GaN buffer layer　　　　　　　　　　　　　　　
  M. Kakuda; S. Morikawa; S. Kuboya; R. Katayama; H. Yaguchi; K. Onabe
  Journal of Crystal Growth, Volume：378, First page：307, Last page：309, 2013, [Reviewed]
  We fabricated cubic AlN (c-AlN) films on MgO (001) substrates via 2-step c-GaN buffer layer by radio-frequency-plasma-assisted molecular beam epitaxy (RF-MBE). The effect of low temperature c-GaN buffer layer on the surface flatness and crystal quality of c-AlN was investigated by AFM and XRD reciprocal space mapping analysis. We examined optical properties of the c-AlN film by spectroscopic ellipsometry. The absorption edge by the direct transition of the c-AlN film was 5.95 eV caused by the hexagonal phase incorporation. © 2013 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/j.jcrysgro.2012.12.120
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84885422048&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84885422048&origin=inward
  DOI ID：10.1016/j.jcrysgro.2012.12.120, ISSN：0022-0248, ORCID：30384770, SCOPUS ID：84885422048, Web of Science ID：WOS:000323355900078
• Optical Absorption by E+ Miniband of GaAs:N delta-Doped Superlattices　　　　　　　　　　　　　　　
  Shuhei Yagi; Shunsuke Noguchi; Yasuto Hijikata; Shigeyuki Kuboya; Kentaro Onabe; Yoshitaka Okada; Hiroyuki Yaguchi
  2013 IEEE 39TH PHOTOVOLTAIC SPECIALISTS CONFERENCE (PVSC), First page：2490, Last page：2493, 2013, [Reviewed]
  The optical properties of GaAs:N delta-doped superlattices (SLs) are investigated by photoreflectance (PR), photo luminescence (PL) and photoluminescence excitation (PLE) spectroscopy. A direct evidence of the optical absorption due to an E, related band of a GaAs:N delta-doped SLs is indicated as a clear absorption edge at 1.6 eV by PLE. AlGaAs layers fabricated on the both sides of the SL region exclude the effect of GaAs absorption on the PLE spectrum, resulting in the successful detection of the absorption property of the SL. In addition, some preliminary characterization of a solar cell using a GaAs:N delta-doped SL is shown. The photocarrier generation originating from SL miniband absorption is confirmed by quantum efficiency measurements.
  IEEE, English, International conference proceedings
  DOI：https://doi.org/10.1109/PVSC.2013.6744981
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84896474240&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84896474240&origin=inward
  DOI ID：10.1109/PVSC.2013.6744981, ISSN：0160-8371, ORCID：30384768, SCOPUS ID：84896474240, Web of Science ID：WOS:000340054100565
• Model calculations of SiC oxide growth rates at sub-atmospheric pressures using the Si and C emission model　　　　　　　　　　　　　　　
  Yasuto Hijikata; Shuhei Yagi; Hiroyuki Yaguchi; Sadafumi Yoshida
  SILICON CARBIDE AND RELATED MATERIALS 2012, Volume：740-742, First page：833, Last page：+, 2013, [Reviewed]
  We found that the 'Si and C emission model' that we proposed as an oxidation model of SiC could not reproduce the initial oxide growth rates of SiC at sub-atmospheric pressures. The comparison between calculated and observed growth rates suggests that the oxide growth on the oxide surface is enhanced in the initial oxidation stage and thus our oxidation model is inaccurate in the description of the initial surface oxidation. Accordingly, we have reconsidered the parameters on surface oxidation and, as a result, found that a much enlarged oxygen concentration on the oxide surface is necessary for solving the discrepancy between calculated and observed growth rates.
  TRANS TECH PUBLICATIONS LTD, English, International conference proceedings
  DOI：https://doi.org/10.4028/www.scientific.net/MSF.740-742.833
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84874076989&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84874076989&origin=inward
  DOI ID：10.4028/www.scientific.net/MSF.740-742.833, ISSN：0255-5476, ORCID：30384765, SCOPUS ID：84874076989, Web of Science ID：WOS:000319785500198
• Biexciton emission from single isoelectronic traps formed by nitrogen-nitrogen pairs in GaAs　　　　　　　　　　　　　　　
  Kengo Takamiya; Toshiyuki Fukushima; Shuhei Yagi; Yasuto Hijikata; Toshimitsu Mochizuki; Masahiro Yoshita; Hidefumi Akiyama; Shigeyuki Kuboya; Kentaro Onabe; Ryuji Katayama; Hiroyuki Yaguchi
  AIP Conference Proceedings, Volume：1566, First page：538, Last page：+, 2013
  We have studied photoluminescence (PL) from individual isoelectronic traps formed by nitrogen-nitrogen (NN) pairs in GaAs. Sharp emission lines due to exciton and biexciton were observed from individual isoelectronic traps in nitrogen atomic-layer doped (ALD) GaAs. The binding energy of biexciton bound to individual isoelectronic traps was approximately 8 meV. Both the exciton and biexciton luminescence lines show completely random polarization and no fine-structure splitting. These results are desirable to the application to the quantum cryptography used in the field of quantum information technology.
  AIP, English, International conference proceedings
  DOI：https://doi.org/10.1063/1.4848523
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84907305933&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84907305933&origin=inward
  DOI ID：10.1063/1.4848523, ISSN：0094-243X, eISSN：1551-7616, ORCID：30384762, SCOPUS ID：84907305933, Web of Science ID：WOS:000331793000268, 共同研究・競争的資金等ID：11611368
• Biexciton Luminescence from Individual Isoelectronic Traps in Nitrogen delta-Doped GaAs　　　　　　　　　　　　　　　
  Kengo Takamiya; Toshiyuki Fukushima; Shuhei Yagi; Yasuto Hijikata; Toshimitsu Mochizuki; Masahiro Yoshita; Hidefumi Akiyama; Shigeyuki Kuboya; Kentaro Onabe; Ryuji Katayama; Hiroyuki Yaguchi
  APPLIED PHYSICS EXPRESS, Volume：5, Number：11, First page：3, Nov. 2012, [Reviewed]
  We report on the observation of biexciton luminescence from single isoelectronic traps formed by nitrogen-nitrogen pairs in nitrogen delta-doped GaAs. The biexciton luminescence intensity showed a quadratic dependence on the excitation power while the exciton luminescence intensity increased linearly with increasing excitation power. The biexciton binding energy was found to be 8 meV, which is considerably larger than that reported for single InAs quantum dots in GaAs. We have also found that both the biexciton and exciton emission lines show completely unpolarized and no fine-structure splitting. This is suitable for the application to polarization-entangled photon pairs. (C) 2012 The Japan Society of Applied Physics
  IOP PUBLISHING LTD, English, Scientific journal
  DOI：https://doi.org/10.1143/APEX.5.111201
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84869186070&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84869186070&origin=inward
  DOI ID：10.1143/APEX.5.111201, ISSN：1882-0778, eISSN：1882-0786, ORCID：30384774, SCOPUS ID：84869186070, Web of Science ID：WOS:000310867800003, 共同研究・競争的資金等ID：11611368
• Oxygen partial pressure dependence of the SiC oxidation process studied by in-situ spectroscopic ellipsometry　　　　　　　　　　　　　　　
  Keiko Kouda; Yasuto Hijikata; Shuhei Yagi; Hiroyuki Yaguchi; Sadafumi Yoshida
  JOURNAL OF APPLIED PHYSICS, Volume：112, Number：2, First page：6, Jul. 2012, [Reviewed]
  The oxygen partial pressure dependence of the Silicon carbide (SiC) oxidation process was investigated using in-situ spectroscopic ellipsometry at oxygen partial pressures between 1 and 0.02 atm for 4H-SiC (0001) Si-and (000-1) C-faces. Analyses of the interface structure between the oxide and SiC indicate that the interface layer has a modified SiC-like structure around 1 nm thick accompanied by oxide growth; the structure and thickness do not change after an oxide growth of about 7 nm. The oxide thickness dependence of the growth rate at sub-atmospheric oxygen pressures is similar to that at 1 atm pressure, that is, just after oxidation starts, the growth rate rapidly decreases as the oxidation proceeds. After an oxide growth of about 7 nm thick, the deceleration of the growth rate suddenly changes to a gentle slope. The thickness at which deceleration changes depends slightly on both the oxygen partial pressure and surface polarity of the SiC substrate. The origins of these two deceleration stages, i.e., rapid and gentle decelerations, are discussed from their pressure dependencies based on the SiC oxidation model taking into account the interfacial emission of Si and C atoms. The formation and structures of the interface layers are also discussed in relation to the oxidation mechanisms. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4736801]
  AMER INST PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1063/1.4736801
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84865484968&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84865484968&origin=inward
  DOI ID：10.1063/1.4736801, ISSN：0021-8979, eISSN：1089-7550, ORCID：30384777, SCOPUS ID：84865484968, Web of Science ID：WOS:000308424500114
• Micro-Photoluminescence Study on the Influence of Oxidation on Stacking Faults in 4H-SiC Epilayers　　　　　　　　　　　　　　　
  Hikaru Yamagata; Shuhei Yagi; Yasuto Hijikata; Hiroyuki Yaguchi
  APPLIED PHYSICS EXPRESS, Volume：5, Number：5, First page：3, Last page：051302, May 2012, [Reviewed]
  We have investigated the influence of thermal oxidation on stacking faults (SFs) in 4H-SiC epilayers by performing micro-photoluminescence measurements for 4H-SiC substrates before and after thermal oxidation. We found that SF (emission wavelength: similar to 425.5 nm) thought to be a single Shockley stacking fault was expanded by thermal oxidation. In addition, as a result of comparison between before and after Ar annealing, the SF was not extended after Ar annealing. We also found that only the SFs extended by laser irradiation is eliminated by oxidation. (c) 2012 The Japan Society of Applied Physics
  JAPAN SOC APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/APEX.5.051302
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84861398046&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84861398046&origin=inward
  DOI ID：10.1143/APEX.5.051302, ISSN：1882-0778, eISSN：1882-0786, ORCID：30384776, SCOPUS ID：84861398046, Web of Science ID：WOS:000303932500005
• Tem analysis of structural phase transition in MBE grown cubic InN on MgO (001) by MBE: Effect of hexagonal phase inclusion in an c-gan nucleation layer　　　　　　　　　　　　　　　
  Jamreonta Parinyataramas; Sakuntam Sanorpim; Chanchana Thanachayanont; Hiroyuki Yaguchi; Misao Orihara
  Applied Mechanics and Materials, Volume：229-231, First page：219, Last page：222, 2012, [Reviewed]
  Cubic GaN buffer layer has been used as a nucleation layer to achieve cubic InN layer on MgO (001) substrate grown by molecular beam epitaxy. The highest cubic phase purity of 85% was examined for the cubic InN layer grown on cubic GaN nucleation layer with hexagonal phase inclusion of 4%. It is found that hexagonal phase inclusion in cubic GaN nucleation layer significantly induced structural phase transition in cubic InN layer, which were verified by transmission electron microscopy (TEM). Cross-sectional dark-field TEM images demonstrate parts of stacking faults in cubic GaN nucleation layer, which were observed to generate stacking faults in the cubic InN grown layer. © (2012) Trans Tech Publications, Switzerland.
  International conference proceedings
  DOI：https://doi.org/10.4028/www.scientific.net/AMM.229-231.219
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84871375602&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84871375602&origin=inward
  DOI ID：10.4028/www.scientific.net/AMM.229-231.219, ISSN：1660-9336, eISSN：1662-7482, ORCID：30384780, SCOPUS ID：84871375602
• Single Photon Generation from Nitrogen Atomic-Layer Doped Gallium Arsenide　　　　　　　　　　　　　　　
  Kengo Takamiya; Yuta Endo; Toshiyuki Fukushima; Shuhei Yagi; Yasuto Hijikata; Toshimitsu Mochizuki; Masahiro Yoshita; Hidefumi Akiyama; Shigeyuki Kuboya; Kentaro Onabe; Ryuji Katayama; Hiroyuki Yaguchi
  THERMEC 2011, PTS 1-4, Volume：706-709, First page：2916, Last page：+, 2012, [Reviewed]
  We have studied the properties of photoluminescence (PL) from individual isoelectronic traps formed by nitrogen-nitrogen (NN) pairs in nitrogen atomic-layer doped (ALD) GaAs. Micro-PL measurements were performed to investigate the properties of single photons generated from individual isoelectronic traps. Twin PL peaks were observed from individual isoelectronic traps in nitrogen ALD GaAs(001). The PL transitions at longer and shorter wavelength sides were linearly polarized in the [110] and [1-10] directions, respectively. The peak splitting and polarization properties can be explained by some in-plane anisotropy most likely due to strain in host crystal. From individual isoelectronic traps in nitrogen ALD GaAs(111), a single PL peak with random polarization was observed, showing that the growth on (111) surface is an effective way to obtain unpolarized single photons. As for nitrogen ALD GaAs(110), different polarization properties were obtained depending on the atomic configuration of NN pairs. in addition, we have used AlGaAs layers to diminish the in-plane anisotropy and could successfully obtained single emission lines with unpolarized character. Introducing AlGaAs layers was also useful for improving the luminescence efficiency.
  TRANS TECH PUBLICATIONS LTD, English, International conference proceedings
  DOI：https://doi.org/10.4028/www.scientific.net/MSF.706-709.2916
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84856180201&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84856180201&origin=inward
  DOI ID：10.4028/www.scientific.net/MSF.706-709.2916, ISSN：0255-5476, ORCID：30384779, SCOPUS ID：84856180201, Web of Science ID：WOS:000308517301220, 共同研究・競争的資金等ID：11611368
• RF-MBE growth of semipolar InN(10-13) and InGaN(10-13) on GaAs(110)　　　　　　　　　　　　　　　
  Misao Orihara; Shuhei Yagi; Yasuto Hijikata; Hiroyuki Yaguchi
  PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 9, NO 3-4, Volume：9, Number：3-4, First page：658, Last page：661, 2012, [Reviewed]
  We have studied InN and InGaN films grown on GaAs(110) substrates by RF-assisted molecular beam epitaxy. Reflection high-energy diffraction observation and X-ray diffraction (XRD) measurements revealed that the InN films were epitaxially grown with InN(10-13)//GaAs(110). From XRD pole figure measurements, only one InN(0002) peak was found at an angle of 31.8 degrees from the pole, indicating that the semipolar InN films were free from twin crystals. This can be explained by the similarity in the anisotropic structure between InN(10-13) and GaAs(110) surfaces. By using low-temperature InN buffer layers, we could obtain semipolar InN films with a smooth surface. Polarization anisotropy in the photoluminescence peak observed at 0.67 eV from semipolar InN(10-13) was weaker than that from alpha-plane InN, which is reasonable considering the smaller angle between the c-axis and the perpendicular direction to the semipolar InN surface. We have also successfully grown In-rich InGaN(10-13) on GaAs(110) substrates with an InN(10-13) intermediate layer, and observed strong photoluminescence from the semipolar InGaN films. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  WILEY-V C H VERLAG GMBH, English, International conference proceedings
  DOI：https://doi.org/10.1002/pssc.201100365
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84858842029&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84858842029&origin=inward
  DOI ID：10.1002/pssc.201100365, ISSN：1862-6351, eISSN：1610-1642, ORCID：30384778, SCOPUS ID：84858842029, Web of Science ID：WOS:000306521600059
• Influence of off-cut angle of (0001) 4H-SiC on the crystal quality of InN grown by RF-MBE　　　　　　　　　　　　　　　
  P. Jantawongrit; S. Sanorpim; H. Yaguchi; M. Orihara; P. Limsuwan
  Procedia Engineering, Volume：32, First page：882, Last page：887, 2012, [Reviewed]
  The effect of the off-cut angle of a 4H-SiC (0001) substrate on the growth of InN thick layer by RF-plasma assisted molecular beam epitaxy (RF-MBE) has been investigated. The off-cut angle used in this study was inclined from 0° (just surface) toward the [11-20] direction of 4° and 8°. Crystalline quality and surface morphology were remarkably sensitive to the value of off-angle. Higher off-cut angles result in a reduction of the full-widths at half-maximum of HRXRD (0002) ω-scans, compared to that of the layer on the (0001)-just surface. In addition, the full-widths at halfmaximum of μ-Raman scattering spectra at 490 cm-1, which is attributed to E2 (high) phonon mode, was decreased with increase in off-cut angle. Furthermore, In-droplets, which are commonly observed on the (0001) InN grown surface under In rich-growth condition, were found to be suppressed owing to an improvement of a nucleation on the off-cut angle surface. In our case, the use of 8°-off substrate increased film density and growth rate, while a surface roughness was reduced. These results clearly demonstrate that the larger off-cut angles improve the crystalline quality of InN film with reducing the In-droplets due to a higher step surface density on the off-cut angle surface. © 2010 Published by Elsevier Ltd.
  ELSEVIER SCIENCE BV, English, International conference proceedings
  DOI：https://doi.org/10.1016/j.proeng.2012.02.027
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84892615166&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84892615166&origin=inward
  DOI ID：10.1016/j.proeng.2012.02.027, ISSN：1877-7058, ORCID：30384775, SCOPUS ID：84892615166, Web of Science ID：WOS:000393153200127
• Analysis of the Energy Structure of Nitrogen delta-Doped GaAs Superlattices for High Efficiency Intermediate Band Solar Cells　　　　　　　　　　　　　　　
  Shunsuke Noguchi; Shuhei Yagi; Yasuto Hijikata; Kentaro Onabe; Shigeyuki Kuboya; Hiroyuki Yaguchi
  2012 38TH IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE (PVSC), First page：83, Last page：86, 2012, [Reviewed]
  Nitrogen delta-doped GaAs superlattices were fabricated and their energy structures were investigated. Several transitions related to E+ band of nitrogen delta-doped regions were observed in photoreflectance ( PR) spectra at energies ranging 1.5-1.7 eV for the superlattices at which no transitions were observed for uniformly doped GaAsN. The PR signal intensity of E+ related band transitions is significantly higher than those observed in uniformly doped GaAsN. This enhancement of E+ related band transitions is advantageous as an intermediate band material, and thus, nitrogen delta-doped GaAs superlattice structures are expected to be an excellent alternative for the use of intermediate band solar cells.
  IEEE, English, International conference proceedings
  DOI：https://doi.org/10.1109/PVSC.2012.6317573
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84869429937&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84869429937&origin=inward
  DOI ID：10.1109/PVSC.2012.6317573, ISSN：0160-8371, ORCID：30384773, SCOPUS ID：84869429937, Web of Science ID：WOS:000309917800019
• Quantum well double barrier resonant tunneling structures for selective contacts of hot carrier solar cells　　　　　　　　　　　　　　　
  Shuhei Yagi; Yasuto Hijikata; Yoshitaka Okada; Hiroyuki Yaguchi
  Conference Record of the IEEE Photovoltaic Specialists Conference, First page：003309, Last page：003312, 2011, [Reviewed]
  Properties of hot carrier solar cells (HCSC) with several types of selective contacts are analyzed. Quantum dots (QD) based double barrier resonant tunneling structures (DBRTS), quantum well (QW) based DBRTS and single barrier (SB) structures are considered as selective contacts and the possibility of selective contacts consist of simpler structures is studied. The analytical method is based on a detailed balance calculation taking into account the energy distribution of carriers transmitting the selective contacts. Calculated results indicate that the maximum conversion efficiency of HCSC with the absorber band gap of 0.7 eV reaches 64% and 57% for the use of selective contacts consist of a QW-DBRTS and a SB structure, respectively, under full concentrated blackbody radiation at 5760K. Although these values are less than the maximum efficiency of the ideal HCSC (80%) with the same absorber band gap, they are still considerably higher than the efficiency limit of conventional solar cells. Due to its simplicity and maturity of fabrication technique, to use selective contacts consist of simpler structures such as QW-DBRTS and SB structures should be reasonable and attractive alternative for experimental investigation on HCSC. © 2011 IEEE.
  International conference proceedings
  DOI：https://doi.org/10.1109/PVSC.2011.6186646
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84861083769&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84861083769&origin=inward
  DOI ID：10.1109/PVSC.2011.6186646, ISSN：0160-8371, ORCID：56291629, SCOPUS ID：84861083769
• Theoretical studies for Si and C emission into SiC layer during oxidation　　　　　　　　　　　　　　　
  Yasuto Hijikata; Hiroyuki Yaguchi; Sadafumi Yoshida
  SILICON CARBIDE AND RELATED MATERIALS 2010, Volume：679-680, First page：429, Last page：+, 2011, [Reviewed]
  To understand the structure of SiC-oxide interface more in detail, we propose a profiling theory of Si and C emission into SiC layer during oxidation. Simulations of the depth profiles of Si and C interstitials results in the structures analogous with those observed from a spectroscopic ellipsometry. To determine the diffusivities of Si and C interstitials, we performed capacitance-voltage measurements for examining the re-distribution profiles of nitrogen after oxidation and compared between observed and calculated profile. The calculated nitrogen profiles showed good fits to the observed ones in the case of self-diffusivity of C interstitials magnified by several 10 times for literature value. Finally, we discuss the validity of the proposed theory.
  TRANS TECH PUBLICATIONS LTD, English, International conference proceedings
  DOI：https://doi.org/10.4028/www.scientific.net/MSF.679-680.429
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=79955121573&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=79955121573&origin=inward
  DOI ID：10.4028/www.scientific.net/MSF.679-680.429, ISSN：0255-5476, ORCID：30384784, SCOPUS ID：79955121573, Web of Science ID：WOS:000291673500102
• Single photon emission from nitrogen delta-doped semiconductors　　　　　　　　　　　　　　　
  Hiroyuki Yaguchi
  QUANTUM SENSING AND NANOPHOTONIC DEVICES VIII, Volume：7945, First page：79452F, Last page：79452F, 2011, [Reviewed]
  Isolated isolectronic traps in semiconductors are promising candidates for single-photon emitters because sharp emission lines with well-defined wavelengths are readily obtained. In this work, we study the emission from individual isoelectronic traps formed by nitrogen-nitrogen pairs in nitrogen delta (delta)-doped GaAs grown on (001) and (111) A substrates. We have found there is a remarkable difference in the polarization properties of luminescence for between (001) and (111) substrates, and successfully obtained unpolarized single photons by utilizing (111) substrate, which are desirable for the application to quantum cryptography. Unpolarized photons could also be obtained from nitrogen delta-doped GaAs/AlGaAs heterostructures grown on (001) substrates.
  SPIE-INT SOC OPTICAL ENGINEERING, English, International conference proceedings
  DOI：https://doi.org/10.1117/12.865770
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=79955781808&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=79955781808&origin=inward
  DOI ID：10.1117/12.865770, ISSN：0277-786X, ORCID：30384783, SCOPUS ID：79955781808, Web of Science ID：WOS:000293695800066
• High cubic-phase purity InN on MgO (001) using cubic-phase GaN as a buffer layer　　　　　　　　　　　　　　　
  S. Sanorpim; S. Kuntharin; J. Parinyataramas; H. Yaguchi; Y. Iwahashi; M. Orihara; Y. Hijikata; S. Yoshida
  AIP Conference Proceedings, Volume：1399, First page：131, Last page：132, 2011, [Reviewed]
  High cubic-phase purity InN films were grown on MgO (001) substrates by molecular beam epitaxy with a cubic-phase GaN buffer layer. The cubic phase purity of the InN grown layers has been analyzed by high resolution X-ray diffraction, μ-Raman scattering and transmission electron microscopy. It is evidenced that the hexagonal-phase content in the InN overlayer much depends on hexagonal-phase content in the cubic-phase GaN buffer layer and increases with increasing the hexagonal-phase GaN content. From Raman scattering measurements, in addition, the InN layer with lowest hexagonal component (6%), only Raman characteristics of cubic TO InN and LO InN modes were observed, indicating a formation of a small amount of stacking faults, which does not affect on vibrational property. © 2011 American Institute of Physics.
  AMER INST PHYSICS, English, International conference proceedings
  DOI：https://doi.org/10.1063/1.3666291
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84855479154&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84855479154&origin=inward
  DOI ID：10.1063/1.3666291, ISSN：0094-243X, eISSN：1551-7616, ORCID：30384782, SCOPUS ID：84855479154, Web of Science ID：WOS:000301053000053
• Photoluminescence from single isoelectronic traps in nitrogen delta-doped GaAs grown on GaAs(1 1 1)A　　　　　　　　　　　　　　　
  T. Fukushima; Y. Hijikata; H. Yaguchi; S. Yoshida; M. Okano; M. Yoshita; H. Akiyama; S. Kuboya; R. Katayama; K. Onabe
  Physica E: Low-Dimensional Systems and Nanostructures, Volume：42, Number：10, First page：2529, Last page：2531, Sep. 2010, [Reviewed]
  We have studied photoluminescence (PL) observed from single isoelectronic traps formed by nitrogen pairs in nitrogen δ-doped GaAs layers grown on GaAs(1 1 1)A substrates. The PL was composed of a single peak with a narrow linewidth of ∼80 μeV. Polarized PL measurements confirmed that the emission from single isoelectronic traps in nitrogen δ-doped GaAs(1 1 1) is unpolarized irrespective of nitrogen pair arrangements. These results can be explained by in-plane isotropy of the samples, which is consistent with the symmetrical property of GaAs(1 1 1), and demonstrate that utilizing (1 1 1) substrate is an effective means for obtaining unpolarized single photons, which are desirable for the application to quantum cryptography. © 2009 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English, International conference proceedings
  DOI：https://doi.org/10.1016/j.physe.2009.12.011
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=77958003985&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=77958003985&origin=inward
  DOI ID：10.1016/j.physe.2009.12.011, ISSN：1386-9477, eISSN：1873-1759, ORCID：30384787, SCOPUS ID：77958003985, Web of Science ID：WOS:000284723200013
• RF-MBE growth of InN on 4H-SiC (0001) with off-angles　　　　　　　　　　　　　　　
  Misao Orihara; Shin Takizawa; Takanori Sato; Yuuki Ishida; Sadafumi Yoshida; Yasuto Hijikata; Hiroyuki Yaguchi
  PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 7, NO 7-8, Volume：7, Number：7-8, First page：2016, Last page：2018, 2010, [Reviewed]
  We have grown InN on 4H-SiC (0001) substrates with various off-angles by RF-N-2 plasma molecular beam epitaxy (RF-MBE). Scanning electron microscope observation revealed that InN films grown on 4H-SiC (0001) substrates with off-angles of 4 degrees and 8 degrees are very smooth and that there are no voids which have often observed for InN epitaxial layers. X-ray diffraction reciprocal space maps for InN grown on 4H-SiC (0001) showed that the c-axes of InN grown on 4H-SiC 4 degrees and 8 degrees off substrates are inclined by 0.35 degrees and 0.8 degrees, respectively, toward the misorientation of the substrate while the c-axis of InN is parallel to that of 4H-SiC for the on-axis substrate. Strong PL peak was observed from InN grown on 4 degrees off substrate at 0.68 eV at 15 K. The PL peak was clearly observed even at room temperature and simply shifted to lower energies with increasing temperature. The difference in the PL peak energy between at 15 K and 300 K was 20 meV, which is reasonable taking into account the difference in the thermal coefficients of InN and SiC. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  WILEY-V C H VERLAG GMBH, English, International conference proceedings
  DOI：https://doi.org/10.1002/pssc.200983441
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=77955823769&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=77955823769&origin=inward
  DOI ID：10.1002/pssc.200983441, ISSN：1862-6351, eISSN：1610-1642, ORCID：30384788, SCOPUS ID：77955823769, Web of Science ID：WOS:000301587600083
• Model calculations of SiC oxide growth rate at various oxidation temperatures based on the silicon and carbon emission model　　　　　　　　　　　　　　　
  Hijikata Yasuto; Yaguchi Hiroyuki; Yoshida Sadafumi
  Materials Science Forum, Volume：645-648, First page：809, Last page：812, 2010, [Reviewed]
  Trans Tech Publications, Scientific journal
  DOI：https://doi.org/10.4028/www.scientific.net/MSF.645-648.809
  DOI ID：10.4028/www.scientific.net/MSF.645-648.809, ISSN：0255-5476, ORCID：30384786, Web of Science ID：WOS:000279657600192
• In-situ Spectroscopic Ellipsometry Study of SiC Oxidation at Low Oxygen-Partial-Pressures　　　　　　　　　　　　　　　
  K. Kouda; Y. Hijikata; H. Yaguchi; S. Yoshida
  SILICON CARBIDE AND RELATED MATERIALS 2009, PTS 1 AND 2, Volume：645-648, First page：813, Last page：+, 2010, [Reviewed]
  We have investigated the oxidation process of SiC (000-1) C-face at low oxygen partial pressures using an in-situ spectroscopic ellipsometry. The oxide growth rate decreased steeply at the early stage of oxidation and then slowly decreased with increasing oxide thickness. The initial oxide growth rate was almost proportional to the oxygen partial pressure for both the polar directions. This result suggests that the initial interfacial reaction rate is constant regardless of the concentration of oxidants reaching the interface.
  TRANS TECH PUBLICATIONS LTD, English, International conference proceedings
  DOI：https://doi.org/10.4028/www.scientific.net/MSF.645-648.813
  DOI ID：10.4028/www.scientific.net/MSF.645-648.813, ISSN：0255-5476, ORCID：30384785, Web of Science ID：WOS:000279657600193
• Optical and electrical characterizations of 4H-SiC-oxide interfaces by spectroscopic ellipsometry and capacitance-voltage measurements　　　　　　　　　　　　　　　
  Hashimoto Hideki; Hijikata Yasuto; Yaguchi Hiroyuki; Yoshida Sadafumi
  Applied Surface Science, Volume：255, Number：20, First page：8648, Last page：8653, Jul. 2009, [Reviewed]
  Scientific journal
  DOI：https://doi.org/10.1016/j.apsusc.2009.06.058
  DOI ID：10.1016/j.apsusc.2009.06.058, ISSN：0169-4332, ORCID：30384794, Web of Science ID：WOS:000268123800057
• A Kinetic Model of Silicon Carbide Oxidation Based on the Interfacial Silicon and Carbon Emission Phenomenon　　　　　　　　　　　　　　　
  Hijikata Yasuto; Yaguchi Hiroyuki; Yoshida Sadafumi
  Applied Physics Express, Volume：2, Number：2, First page：021203, Last page：021203, Feb. 2009, [Reviewed]
  {IOP} Publishing, Scientific journal
  DOI：https://doi.org/10.1143/APEX.2.021203
  DOI ID：10.1143/APEX.2.021203, ISSN：1882-0778, ORCID：30384789, Web of Science ID：WOS:000264942800007
• Model Calculation of SiC Oxidation Rates in the Thin Oxide Regime　　　　　　　　　　　　　　　
  Yasuto Hijikata; Takeshi Yamamoto; Hiroyuki Yaguchi; Sadafumi Yoshida
  SILICON CARBIDE AND RELATED MATERIALS 2007, PTS 1 AND 2, Volume：600-603, First page：663, Last page：666, 2009, [Reviewed]
  To explain the growth rate enhancement of SiC oxidation in the thin oxide regime, which was recently found from the real time monitoring experiments of the initial oxidation stage of SiC (000-1) C-face using an in-situ spectroscopic ellipsometer, we tried to apply the interfacial Si emission model, which has been originally proposed for Si oxidation, and found that the Si emission model successfully reproduced the SiC oxidation rates at the whole range of oxide thickness and at oxidation temperatures measured. By comparing with the simulations for Si oxidation, we have discussed the oxidation mechanism of SiC.
  TRANS TECH PUBLICATIONS LTD, English, International conference proceedings
  DOI：https://doi.org/10.4028/www.scientific.net/MSF.600-603.663
  DOI ID：10.4028/www.scientific.net/MSF.600-603.663, ISSN：0255-5476, ORCID：48141545, Web of Science ID：WOS:000263555300158
• Oxygen-Partial-Pressure Dependence of SiC Oxidation Rate Studied by In-situ Spectroscopic Ellipsometry　　　　　　　　　　　　　　　
  Takeshi Yamamoto; Yasuto Hijikata; Hiroyuki Yaguchi; Sadafumi Yoshida
  SILICON CARBIDE AND RELATED MATERIALS 2007, PTS 1 AND 2, Volume：600-603, First page：667, Last page：670, 2009, [Reviewed]
  Real time observations of SiC (000-1) C-face and (0001) Si-face oxidation were performed using an in-situ ellipsometer over the oxygen-partial-pressure range from 0.1 to 1.0 atm. We analyzed the relations between oxide growth rate and oxide thickness by applying an empirical relation proposed by Massoud et al. We found the occurrence of oxidation enhancement in the thin oxide regime also for Si-face as well as for C-face. We have discussed the oxygen-partial-pressure dependence of the oxidation rate constants between SiC C- and Si face, comparing with that of Si. © (2009) Trans Tech Publications, Switzerland.
  TRANS TECH PUBLICATIONS LTD, English, International conference proceedings
  DOI：https://doi.org/10.4028/www.scientific.net/MSF.600-603.667
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=60349127717&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=60349127717&origin=inward
  DOI ID：10.4028/www.scientific.net/MSF.600-603.667, ISSN：0255-5476, ORCID：48141546, SCOPUS ID：60349127717, Web of Science ID：WOS:000263555300159
• Observation of SiC Oxidation in Ultra-thin Oxide Regime by In-situ Spectroscopic Ellipsometry　　　　　　　　　　　　　　　
  Toshiyuki Takaku; Yasuto Hijikata; Hiroyuki Yaguchi; Sadafumi Yoshida
  SILICON CARBIDE AND RELATED MATERIALS 2008, Volume：615-617, First page：509, Last page：512, 2009, [Reviewed]
  Thermal oxidation process of silicon carbide in ultra-thin oxide regime has been studied by performing in-situ and real time spectroscopic ellipsometry. We found the thermal oxidation at 700°C forms no or extremely thin interface layers between SiC and oxide layers. In contrast, the oxidation at 850°C forms an interface layer of around 1 nm in thickness, having similar thickness and optical constants of the interface layers formed by the oxidation at higher temperature than 1000°C. To make clear the conditions no interface layer is formed, i.e., whether low temperature growth or thin oxide thickness is crucial, we have performed the oxidation at 850°C in the reduced oxygen pressure. Based on the results of these experiments, we discussed the origin of the formation of interface layers as well as the oxidation mechanism of SiC. © (2009) Trans Tech Publications.
  TRANS TECH PUBLICATIONS LTD, English, International conference proceedings
  DOI：https://doi.org/10.4028/www.scientific.net/MSF.615-617.509
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=77955444151&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=77955444151&origin=inward
  DOI ID：10.4028/www.scientific.net/MSF.615-617.509, ISSN：0255-5476, ORCID：48141803, SCOPUS ID：77955444151, Web of Science ID：WOS:000265961100122
• Characterization of 4H-SiC-SiO2 Interfaces by a Deep Ultraviolet Spectroscopic Ellipsometer　　　　　　　　　　　　　　　
  H. Seki; T. Wakabayashi; Y. Hijikata; H. Yaguchi; S. Yoshida
  SILICON CARBIDE AND RELATED MATERIALS 2008, Volume：615-617, First page：505, Last page：508, 2009, [Reviewed]
  We have characterized 4H-SiC-oxide interfaces fabricated by thermal oxidation of SiC using spectroscopic ellipsometry in the wide spectral range from visible to deep UV region. It was found that there exists an interface layer, around 1 nm in thickness, regardless of the oxide thickness from 15 nm to 40 nm. The optical constants of the interface layer have similar spectral dependence to those of SiC, though the absolute value of the refractive indices is 0.5-1 larger than that of SiC. We have discussed the structure of the interface layer based oil the oxidation mechanism of SiC, like the Si-emission model.
  TRANS TECH PUBLICATIONS LTD, English, Scientific journal
  DOI：https://doi.org/10.4028/www.scientific.net/MSF.615-617.505
  DOI ID：10.4028/www.scientific.net/MSF.615-617.505, ISSN：0255-5476, ORCID：48141548, Web of Science ID：WOS:000265961100121
• Model Calculation of SiC Oxide Growth Rate Based on the Silicon and Carbon Emission Model　　　　　　　　　　　　　　　
  Yasuto Hijikata; Hiroyuki Yaguchi; Sadafumi Yoshida
  SILICON CARBIDE AND RELATED MATERIALS 2008, Volume：615-617, First page：489, Last page：492, 2009, [Reviewed]
  We proposed a kinetic model For SiC oxidation, named 'silicon and carbon (Si-C) emission model', taking into account the emission of Si and C atoms from the SiC-oxide interface, which suppresses the oxidation rate at the interface. Based oil the model, we calculated oxide growth rates for SiC (0001) Si- and (000-1) C-face and found that the calculated values exhibit good fits to the measured ones in the entire oxide thickness range for both faces. We also calculated depth profiles of Si and C interstitials and oxidants, and discussed the oxidation mechanism of SiC as well as the difference in the oxidation process of Si-face and C-face.
  TRANS TECH PUBLICATIONS LTD, English, International conference proceedings
  DOI：https://doi.org/10.4028/www.scientific.net/MSF.615-617.489
  DOI ID：10.4028/www.scientific.net/MSF.615-617.489, ISSN：0255-5476, Web of Science ID：WOS:000265961100117
• Oxide Growth Rate Enhancement of Silicon Carbide (0001) Si-Faces in Thin Oxide Regime　　　　　　　　　　　　　　　
  Yamamoto Takeshi; Hijikata Yasuto; Yaguchi Hiroyuki; Yoshida Sadafumi
  Japanese Journal of Applied Physics, Volume：47, Number：10, First page：7803, Last page：7806, Oct. 2008, [Reviewed]
  Scientific journal
  DOI：https://doi.org/10.1143/JJAP.47.7803
  DOI ID：10.1143/JJAP.47.7803, ISSN：0021-4922, ORCID：30384797, Web of Science ID：WOS:000260443900009
• Twin photoluminescence peaks from single isoelectronic traps in nitrogen delta-doped GaAs　　　　　　　　　　　　　　　
  Y. Endo; Y. Hijikata; H. Yaguchi; S. Yoshida; M. Yoshita; H. Akiyama; F. Nakajima; R. Katayama; K. Onabe
  PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, Volume：40, Number：6, First page：2110, Last page：2112, Apr. 2008, [Reviewed]
  We report on twin emission peaks observed from single isoelectronic traps formed by nitrogen pairs in nitrogen delta-doped GaAs by high-energy resolution micro-photoluminescence (PL) spectroscopy. The twin PL peaks show almost the same intensity with narrow linewidths of 20-50 mu eV, which are considerably smaller than that ever reported for isoelectronic traps in GaAs:N. The higher and lower energy luminescence transitions were linearly polarized in the [1 (1) over bar 0] and [1 1 0] directions, respectively, indicating that the two exciton states have completely orthogonal relations with each other. The fact that any pair of the twin PL peaks has the same polarization properties suggests that the splitting is due to the anisotropy between [1 (1) over bar 0] and [1 1 0] directions in the host crystal and is possibly explained by the strain anisotropy in the sample. (C) 2007 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/j.physe.2007.10.047
  DOI ID：10.1016/j.physe.2007.10.047, ISSN：1386-9477, ORCID：30384800, Web of Science ID：WOS:000255717400104
• High resolution X- ray diffraction and raman scattering studies of cubic-phase InN films grown by MBE　　　　　　　　　　　　　　　
  S. Kuntharin; S. Sanorpim; H. Yaguchi; Y. Iwahashi; M. Orihara; Y. Hijakata; S. Yoshida
  Advanced Materials Research, Volume：55-57, First page：773, Last page：776, 2008, [Reviewed]
  We demonstrate the use of high resolution X-ray diffraction and Raman scattering to assess the generation of hexagonal-phase in the cubic-phase InN (c-InN) films on MgO substrates grown by molecular beam epitaxy with a cubic-phase GaN buffer layer. The X-ray reciprocal-lattice space mapping was used to examine the hexagonal-phase generated on the cubic (111) planes in the c-InN films. Ratio of hexagonal to cubic components in the c-InN grown layers was estimated from the ratio of the integrated X-ray diffraction intensities of cubic (002) and hexagonal (10-11) reflections measured by co-scans. Amount of hexagonal-phase presented in the c-InN films was determined in the range of 6 to 24%. It was found that the Raman characteristics are also sensitive to hexagonal-phase presented in the c-InN films. For the lowest amount of hexagonal-phase (6%), only Raman scattering characteristics of c-InN was observed, indicating formation of a small amount of stacking faults, which not affected on the vibrational property. Based on our results, relatively easy access to the generation of hexagonal-phase suggests that it may be very useful for HRXRD and Raman scattering measurements of c-InN. © 2008 Trans Tech Publications, Switzerland.
  International conference proceedings
  DOI：https://doi.org/10.4028/www.scientific.net/amr.55-57.773
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=63049097802&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=63049097802&origin=inward
  DOI ID：10.4028/www.scientific.net/amr.55-57.773, ISSN：1022-6680, SCOPUS ID：63049097802
• Photoluminescence study of hexagonal InN/InGaN quantum well structures grown on 3C-SiC (001) substrates by molecular beam epitaxy　　　　　　　　　　　　　　　
  S. Hirano; T. Inoue; G. Shikata; M. Orihara; Y. Hijikata; H. Yaguchi; S. Yoshida; Y. Hirabayashi
  PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 5, NO 6, Volume：5, Number：6, First page：1730, Last page：+, 2008, [Reviewed]
  We have studied photoluminescence from hexagonal InN/InGaN multiple quantum well structures grown on 3C-SiC (001) substrates with an InGaN underlayer by plasma assisted-molecular beam epitaxy. We have observed photoluminescence spectra of InN/InGaN MQWs with various well widths. The photoluminescence peak related to quantum wells was clearly observed even at room temperature and found to shift to higher energies with decreasing well width due to the quantum confinement effect. We also discuss the effect of the built-in electric fields on the PL peak energy. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  WILEY-V C H VERLAG GMBH, English, International conference proceedings
  DOI：https://doi.org/10.1002/pssc.200778606
  DOI ID：10.1002/pssc.200778606, ISSN：1862-6351, ORCID：30384799, Web of Science ID：WOS:000256695700075
• Photoluminescence of cubic InN films on MgO (001) substrates　　　　　　　　　　　　　　　
  T. Inoue; Y. Iwahashi; S. Oishi; M. Orihara; Y. Hijikata; H. Yaguchi; S. Yoshida
  PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 5, NO 6, Volume：5, Number：6, First page：1579, Last page：1581, 2008, [Reviewed]
  We have studied photoluminescence from cubic InN films grown on MgO substrates with a cubic GaN underlayer by RF N(2) plasma molecular beam epitaxy. A single PL peak was observed at 0.47 eV. By analyzing the reflectance spectra of cubic InN films, we could derive the refractive index and extinction coefficient, and found the band gap energy of cubic InN is 0.48 eV, indicating that the PL peak observed at 0.47 eV is due to the interband transition of cubic InN. The difference in the PL peak energy between hexagonal and cubic InN is in good agreement with that predicted by ab-initio calculations.
  WILEY-V C H VERLAG GMBH, English, International conference proceedings
  DOI：https://doi.org/10.1002/pssc.200778505
  DOI ID：10.1002/pssc.200778505, ISSN：1862-6351, ORCID：30384798, Web of Science ID：WOS:000256695700031
• Improvement of the surface morphology of a-plane InN using low-temperature InN buffer layers　　　　　　　　　　　　　　　
  G. Shikata; S. Hirano; T. Inoue; M. Orihara; Y. Hijikata; H. Yaguchi; S. Yoshida
  PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 5, NO 6, Volume：5, Number：6, First page：1808, Last page：1810, 2008, [Reviewed]
  We report on the improvement of the surface morphology of a-plane InN films grown by RF molecular beam epitaxy. By using low-temperature (LT) InN buffer layers, we could successfully obtain InN films with a smooth surface, The full width at half maximum values of the x-ray diffraction (11-20) rocking curve along the [0001] InN direction were 2870 arcsec and 3410 arcsec for a-plane InN samples grown at 500 degrees C with and without LT-InN buffer layers, respectively. Thus, we-could improve also the crystalline quality of a-plane InN films by using LT-InN buffer layers. We observed strong polarization anisotropy in the photoluminescence spectra of a-plane InN, which is typical of nonpolar wurtzite III-nitride films.
  WILEY-V C H VERLAG GMBH, English, International conference proceedings
  DOI：https://doi.org/10.1002/pssc.200778662
  DOI ID：10.1002/pssc.200778662, ISSN：1862-6351, ORCID：30384796, Web of Science ID：WOS:000256695700100
• Growth rate enhancement of (0001)-face silicon-carbide oxidation in thin oxide regime　　　　　　　　　　　　　　　
  Yamamoto Takeshi; Hijikata Yasuto; Yaguchi Hiroyuki; Yoshida Sadafumi
  Japanese Journal of Applied Physics Part 2-Letters & Express Letters, Volume：46, Number：29-32, First page：L770, Last page：L772, Aug. 2007, [Reviewed]
  Scientific journal
  DOI：https://doi.org/10.1143/JJAP.46.L770
  DOI ID：10.1143/JJAP.46.L770, ISSN：0021-4922, ORCID：30384801, Web of Science ID：WOS:000249166000018
• RF-MBE growth of a-plane InN on r-plane sapphire with a GaN underlayer　　　　　　　　　　　　　　　
  G. Shikata; S. Hirano; T. Inoue; M. Orihara; Y. Hijikata; H. Yaguchi; S. Yoshida
  JOURNAL OF CRYSTAL GROWTH, Volume：301, First page：517, Last page：520, Apr. 2007, [Reviewed]
  a-Plane InN films were grown on r-plane sapphire substrates with GaN underlayers by RF-N-2 plasma molecular beam epitaxy (MBE). X-ray diffraction (XRD) measurements and reflection high-energy electron diffraction (RHEED) observation revealed that the InN films were grown with InN (1 1 (2) over bar 0)parallel to GaN (1 1 (2) over bar 0)parallel to sapphire (2 (2) over bar 0 4). We have carried out micro-Raman scattering measurements for a-plane InN film. Raman peaks were observed at 448, 490 and 598 cm(-1), which can be identified as the A(1) transversal optical (TO), E-2 (high) and E-1 longitudinal optical (LO) mode phonon, respectively. We also carried out photoluminescence (PL) measurements for a-plane InN film. Strong PL was observed between 0.62 and 0.65 eV, which is the lowest ever reported for InN. It is suggested from the excitation intensity and temperature dependence of the PL spectra that the red shift of the PL peak is due to the Franz-Keldysh effect. (c) 2006 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/j.jcrysgro.2006.11.072
  DOI ID：10.1016/j.jcrysgro.2006.11.072, ISSN：0022-0248, eISSN：1873-5002, ORCID：30384808, Web of Science ID：WOS:000246015800119
• RF-MBE growth of InN/InGaN quantum well structures on 3C-SiC substrates　　　　　　　　　　　　　　　
  S. Hirano; T. Inoue; G. Shikata; M. Orihara; Y. Hijikata; H. Yaguchi; S. Yoshida
  JOURNAL OF CRYSTAL GROWTH, Volume：301, First page：513, Last page：516, Apr. 2007, [Reviewed]
  InN/In0.83Ga0.17N multiple quantum well (MQW) structures have been fabricated on 3C-SiC (0 0 1) substrates by radio-frequency plasma-assisted molecular beam epitaxy (RF-MBE). The surface morphology, structural properties, and optical properties of the samples were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL), respectively. XRD satellite peaks due to the periodic structure were clearly observed in the MQW structures grown at temperatures lower than 530 degrees C. PL emissions from the MQW were observed around 0.85 eV. (c) 2006 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/j.jcrysgro.2006.11.117
  DOI ID：10.1016/j.jcrysgro.2006.11.117, ISSN：0022-0248, ORCID：30384809, Web of Science ID：WOS:000246015800118
• Simultaneous determination of the carrier concentration, mobility and thickness of SiC homo-epilayers using terahertz reflectance spectroscopy　　　　　　　　　　　　　　　
  Shingo Oishi; Yasuto Hijikata; Hiroyuki Yaguchi; Sadafumi Yoshida
  SILICON CARBIDE AND RELATED MATERIALS 2006, Volume：556-557, First page：423, Last page：+, 2007, [Reviewed]
  We have simultaneously determined the carrier concentration, mobility, and thickness of 414-SiC homo-epilayers with carrier concentration of 10(16)-10(18) cm(-3) from reflectance spectroscopy in the wavenumber range of 20-2000 cm(-1). The spectra at 20-100 cm(-1) and at 80-2000 cm(-1) were measured by using the terahertz time domain spectrometer (THz-TDS) and the Fourier-transform infrared (FTIR) spectrometer, respectively. A modified classical dielectric function (MDF) model was employed for the curve fitting. We have compared the values of free carrier concentrations estimated from the reflectance spectroscopy with the net doping concentrations obtained from C-V measurements, and have discussed the validity of the electrical properties estimated from the reflectance spectroscopy.
  TRANS TECH PUBLICATIONS LTD, English, International conference proceedings
  DOI：https://doi.org/10.4028/www.scientific.net/MSF.556-557.423
  DOI ID：10.4028/www.scientific.net/MSF.556-557.423, ISSN：0255-5476, ORCID：48141549, Web of Science ID：WOS:000249653900101
• Structural and optical characterization of high In content cubic InGaN on GaAs(001) substrates by RF-MBE　　　　　　　　　　　　　　　
  Nakamura Teruyuki; Endo Yuta; Katayama Ryuji; Yaguchi Hiroyuki; Onabe Kentaro
  physica status solidi (c), Volume：4, Number：7, First page：2437, Last page：2440, 2007, [Reviewed]
  Wiley, Scientific journal
  DOI：https://doi.org/10.1002/pssc.200674803
  DOI ID：10.1002/pssc.200674803, ISSN：1862-6351, eISSN：1610-1642, ORCID：30384811, Web of Science ID：WOS:000248047600056
• Photoluminescence study of isoelectronic traps in dilute GaAsN alloys　　　　　　　　　　　　　　　
  H. Yaguchi; T. Aoki; T. Morioke; Y. Hijikata; S. Yoshida; M. Yoshita; H. Akiyama; D. Aoki; K. Onabe
  Physica Status Solidi (C) Current Topics in Solid State Physics, Volume：4, Number：7, First page：2760, Last page：2763, 2007, [Reviewed]
  We have studied photoluminescence spectra in detail to clarify the character of the isoelectronic traps in dilute GaAsN alloys. Several sharp lines have been observed at the lower energy side of the GaAs bandgap and are in good agreement with the nitrogen pair-related emission lines previously reported. In addition to the nitrogen pair-related lines, some other emission lines have been also observed. Compared with the energies of these emission lines and the nitrogen pair-related emission lines, it was found that the energy differences agree with the longitudinal optical phonon energy at the Γ point of GaAs, showing that the character of isoelectronic traps due to nitrogen pairs in dilute GaAsN alloys is significantly contributed from the conduction band state at the Γ point. The temperature dependence of the peak energy of luminescence due to nitrogen pairs also indicates that the character of isoelectronic traps in dilute GaAsN alloys is due to the conduction band edge state at the Γ point of GaAs. For a dilute GaAsN alloy with lower nitrogen concentration, we have observed that the intensity of an emission line increased superlinearly with excitation power. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA.
  WILEY-V C H VERLAG GMBH, English, International conference proceedings
  DOI：https://doi.org/10.1002/pssc.200674721
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=49749134309&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=49749134309&origin=inward
  DOI ID：10.1002/pssc.200674721, ISSN：1862-6351, ORCID：30384807, SCOPUS ID：49749134309, Web of Science ID：WOS:000248047600135
• Modulation spectroscopic investigation on lattice polarity of gallium nitride　　　　　　　　　　　　　　　
  Ryuji Katayama; Kentaro Onabe; Hiroyuki Yaguchi; Tomonori Matsushita; Takashi Kondo
  Applied Physics Letters, Volume：91, Number：6, 2007, [Reviewed]
  A lattice polarity determination method for GaN is demonstrated, which is based on a capability of modulation spectroscopy for the assignment of electric-field directions performed nondestructively using simple optical setups. A strong spontaneous polarization induces an upward band bending toward +c surfaces and a downward but weaker bending toward -c surfaces for typical films with small residual strains and electron densities. This difference is distinguishable in terms of the spectral-phase flip, utilizing photoreflectance, and electroreflectance. Quantitative analysis revealed the exciton dissociation at a high-field region of +c surfaces consistent with the band profile derived as a solution of Poisson equation. © 2007 American Institute of Physics.
  Scientific journal
  DOI：https://doi.org/10.1063/1.2764115
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=34547842633&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=34547842633&origin=inward
  DOI ID：10.1063/1.2764115, ISSN：0003-6951, ORCID：30384806, SCOPUS ID：34547842633, Web of Science ID：WOS:000248661400044
• Micro-photoluminescence study of nitrogen delta-doped GaAs grown by metalorganic vapor phase epitaxy　　　　　　　　　　　　　　　
  Y. Endo; K. Tanioka; Y. Hijikata; H. Yaguchi; S. Yoshida; M. Yoshita; H. Akiyama; W. Ono; F. Nakajima; R. Katayama; K. Onabe
  JOURNAL OF CRYSTAL GROWTH, Volume：298, First page：73, Last page：75, Jan. 2007, [Reviewed]
  We have measured micro-photoluminescence (PL) spectra of nitrogen delta (delta)-doped GaAs with various concentrations. In nitrogen delta-doped GaAs with low concentrations, the micro-PL spectra measured at different positions were individually different. In contrast, almost the same spectra were obtained for nitrogen delta-doped GaAs with higher concentrations and uniformly nitrogen-doped GaAs. The micro-PL study shows that there are no more than a few isoelectronic traps within a diameter of similar to 1 mu m. This indicates a good prospect for applications of isoelectronic traps to single photon emitting devices. (c) 2006 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/j.jcrysgro.2006.10.019
  DOI ID：10.1016/j.jcrysgro.2006.10.019, ISSN：0022-0248, ORCID：30384804, Web of Science ID：WOS:000244622600017
• Micro-Raman study on the improvement of luminescence efficiency of GaAsN alloys　　　　　　　　　　　　　　　
  K. Tanioka; Y. Endo; Y. Hijikata; H. Yaguchi; S. Yoshida; M. Yoshita; H. Akiyama; K. Onabe
  JOURNAL OF CRYSTAL GROWTH, Volume：298, First page：131, Last page：134, Jan. 2007, [Reviewed]
  We have used in situ micro-Raman spectroscopy to clarify the mechanism of the luminescence efficiency improvement of GaAsN alloys by laser irradiation. Raman peak intensity of GaAs-like longitudinal optical (LO) mode phonon was observed to increase with the laser irradiation time. With increasing laser power density, the Raman intensity of GaAs-like LO mode phonon was found to increase more rapidly and to be saturated in a shorter time. Changes in the Raman intensity can be expressed by the same equation used for the luminescence efficiency improvement. Time constants of changes in the Raman intensity were almost in agreement with those of the luminescence efficiency improvement. This indicates that the increase in Raman intensity of GaAs-like LO phonon is closely related to the luminescence efficiency improvement. (c) 2006 Published by Elsevier B.V.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/j.jcrysgro.2006.10.006
  DOI ID：10.1016/j.jcrysgro.2006.10.006, ISSN：0022-0248, eISSN：1873-5002, ORCID：30384805, Web of Science ID：WOS:000244622600030
• Simultaneous determination of carrier concentration, mobility, and thickness of SiC homoepilayers by infrared reflectance spectroscopy　　　　　　　　　　　　　　　
  Shingo Oishi; Yasuto Hijikata; Hiroyuki Yaguchi; Sadafumi Yoshida
  Japanese Journal of Applied Physics, Part 2: Letters, Volume：45, Number：46-50, First page：L1226, Last page：L1229, Dec. 2006, [Reviewed]
  We have simultaneously determined the carrier concentration, mobility, and thickness of 4H-SiC homoepilayers with carrier concentrations of 10 17-1018 cm-3 from infrared reflectance measurements with the wave number range of 80-2000 cm-1. A modified classical dielectric function model was employed for the fitting analyses. We have prepared n-type epilayers on p-type and n-type substrates for comparison with the values of the carrier concentration and mobility estimated from infrared reflectance measurements with those obtained from Hall-effect measurements and C-V measurements. Through these comparisons, we have confirmed the validity of the values estimated from infrared reflectance measurements. © 2006 The Japan Society of Applied Physics.
  INST PURE APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.45.L1226
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=34547874643&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=34547874643&origin=inward
  DOI ID：10.1143/JJAP.45.L1226, ISSN：0021-4922, eISSN：1347-4065, ORCID：30384817, SCOPUS ID：34547874643, Web of Science ID：WOS:000243208300002
• Characterization of oxide films on 4H-SiC epitaxial (000(1)over-bar) faces by high-energy-resolution photoemission spectroscopy: Comparison between wet and dry oxidation　　　　　　　　　　　　　　　
  Hijikata Yasuto; Yaguchi Hiroyuki; Yoshida Sadafumi; Takata Yasutaka; Kobayashi Keisuke; Nohira Hiroshi; Hattori Takeo
  Journal of Applied Physics, Volume：100, Number：5, Sep. 2006, [Reviewed]
  Scientific journal
  DOI：https://doi.org/10.1063/1.2345471
  DOI ID：10.1063/1.2345471, ISSN：0021-8979, ORCID：30384812, Web of Science ID：WOS:000240602500065
• Off-angle dependence of characteristics of 4H-SiC-oxide interfaces　　　　　　　　　　　　　　　
  Y. Hijikata; H. Yaguchi; S. Yoshida; Y. Takata; K. Kobayashi; H. Nohira; T. Hattori
  Silicon Carbide and Related Materials 2005, Pts 1 and 2, Volume：527-529, First page：1003, Last page：1006, 2006, [Reviewed]
  SiC-Oxide interfaces on 4H-SiC epitaxial substrates of various off-angles have been characterized by C-V measurements, synchrotron radiation excited photoemission spectroscopy and atomic force microscopy. We found that the interface state density (N-it) and the amount of sub-oxides (S-i) for small off-angle substrates were smaller than those for large off-angle ones. It was also found that there is a good correlation between the amount of the interface states and that of sub-oxides. Step-terrace structures were clearly observed in the surface morphology after the removal of oxide layers for small off-angle substrates, which shows that the interfaces were atomically smooth. These results suggest that the small N-it and S-i values for small off-angle substrates relate to the smoothness of the interface and that high performance SiC MOS devices are expected by using small off-angle substrates.
  TRANS TECH PUBLICATIONS LTD, English, International conference proceedings
  DOI：https://doi.org/10.4028/www.scientific.net/MSF.527-529.1003
  DOI ID：10.4028/www.scientific.net/MSF.527-529.1003, ISSN：0255-5476, ORCID：48141550, Web of Science ID：WOS:000244227200235
• Real time observation of SiC oxidation using an in-situ ellipsometer　　　　　　　　　　　　　　　
  Kakubari K; Kuboki R; Hijikata Y; Yaguchi H; Yoshida S; Devaty RP
  Materials Science Forum, Volume：527-529, First page：1031, Last page：1034, 2006, [Reviewed]
  Scientific journal
  DOI：https://doi.org/10.4028/WWW.SCIENTIFIC.NET/MSF.527-529.1031
  DOI ID：10.4028/WWW.SCIENTIFIC.NET/MSF.527-529.1031, ORCID：30384815, Web of Science ID：WOS:000244227200242
• RF-MBE growth of cubic InN films on MgO (001) substrates　　　　　　　　　　　　　　　
  Y. Iwahashi; H. Yaguchi; A. Nishimoto; M. Orihara; Y. Hijikata; S. Yoshida
  PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 3, NO 6, Volume：3, Number：6, First page：1515, Last page：1518, 2006, [Reviewed]
  Cubic InN films have been grown on MgO substrates with cubic GaN underlayers by RF-N-2 plasma MBE. By changing the growth conditions, we clarified the growth temperature and In flux dependence of the quality of cubic InN films. It was found the surface of cubic InN films grown at relatively higher temperatures was smooth and that the hexagonal phase content in the InN films decreased with increasing In flux. Based on the findings, we have successfully obtained a c-InN film with high phase-purity and a smooth surface. We have carried out micro Raman scattering measurements for the high-quality cubic InN film. Raman peaks were clearly observed at 596 cm(-1) and 467 cm(-1), which are attributed to longitudinal optical and transverse optical phonon modes of cubic InN, respectively. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  WILEY-VCH, INC, English, International conference proceedings
  DOI：https://doi.org/10.1002/pssc.200565312
  DOI ID：10.1002/pssc.200565312, ISSN：1862-6351, ORCID：30384816, Web of Science ID：WOS:000239543600033
• Photo-induced improvement of radiative efficiency and structural changes in GaAsN alloys　　　　　　　　　　　　　　　
  H. Yaguchi; T. Morioke; T. Aoki; H. Shimizu; Y. Hijikata; S. Yoshida; M. Yoshita; H. Akiyama; N. Usami; D. Aoki; K. Onabe
  PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 3, NO 6, Volume：3, Number：6, First page：1907, Last page：1910, 2006, [Reviewed]
  We have investigated the excitation power density and nitrogen concentration dependence of the changes in the radiative efficiency of GaAsN alloys to examine the mechanism of the photo-induced improvement of radiative efficiency. With increasing excitation power density, the radiative efficiency increased more rapidly. The measure of the improvement I-after/I-before superlinearly increased with increasing nitrogen concentration x up to similar to 1%. This suggests that the nonradiative recombination centers eliminated by photoexcitation are not defects formed by a single nitrogen atom but complexes formed by gathering of several nitrogen atoms. Micro Raman study revealed that the GaAs-like LO mode phonon peak intensity increased with photoexcitation time in a similar way to the increase in the radiative efficiency. Considering that this phenomenon is in a time scale of several seconds, the photo-induced structural changes correspond not to long range inter-diffusion but to local changes in atomic configuration which lead to the decrease in the density of nonradiative recombination centers. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  WILEY-VCH, INC, English, International conference proceedings
  DOI：https://doi.org/10.1002/pssc.200565372
  DOI ID：10.1002/pssc.200565372, ISSN：1862-6351, ORCID：30384814, Web of Science ID：WOS:000239543600124
• Effect of Ar post-oxidation annealing on oxide-4H-SiC interfaces studied by capacitance to voltage measurements and photoemission spectroscopy　　　　　　　　　　　　　　　
  Y Hijikata; H Yaguchi; S Yoshida; Y Ishida; M Yoshikawa
  JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A, Volume：23, Number：2, First page：298, Last page：303, Mar. 2005, [Reviewed]
  The effect of post-oxidation annealing in Ar atmosphere (Ar POA) on 4H-SiC-oxide interfaces. has been studied by capacitance to gate-bias voltage (C-V) measurements and photoemission spectroscopy (PES). It was found from the C-V measurements that the shift of the C-V curve disappears when the Ar POA temperature is higher than 600&DEG; C. On the other hand, angle-resolved x-ray photoelectron spectroscopy measurements revealed that the thickness of the intermediate layers containing Si1+ oxidation states observed at the interfaces decreases abruptly when the Ar POA temperature exceeds 500&DEG; C. In ultraviolet photoelectron spectra, O2p, peaks were changed by Ar POA at temperatures higher than 600&DEG; C, which is the temperature where the shift of the C-V curve disappears in C-V measurements. This shows that the change in O2p bonding by Ar POA is the origin of the shift observed in C-V characteristics. A model of structural changes in the interfaces by Ar POA has been proposed based on the results of PES measurements and those of C-V measurements. © 2005 American Vacuum Society.
  A V S AMER INST PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1116/1.1865153
  DOI ID：10.1116/1.1865153, ISSN：0734-2101, eISSN：1520-8559, ORCID：30384819, Web of Science ID：WOS:000227739200013
• Characterization of oxide films on SIC epitaxial (000-1) faces by angle-resolved photoemission spectroscopy measurements using synchrotron radiation　　　　　　　　　　　　　　　
  A Hijikata; H Yaguchi; S Yoshida; Y Takata; K Kobayashi; S Shin; H Nohira; T Hattori
  SILICON CARBIDE AND RELATED MATERIALS 2004, Volume：483, First page：585, Last page：588, 2005
  Thermal oxide films on SiC epitaxial (000-1) C-faces have been characterized by angle-resolved photoemission spectroscopy (AR-PES). The structure of wet oxide/SiC C-face interface was compared with that of dry oxide/SiC C-face, as well as that of dry oxide/SiC Si-face, in order to clarify why a MOS device of SiC C-face achieved good electrical properties. The improvement in electrical properties was confirmed by AR-PES measurements, evidencing differences in binding energy between SiC and the Si4+ components in Si2p and valence band region, and in binding energy between SiC and the CH, components in C1s. The reason for the improvement in electrical property of MOS devices by use of SiC C-face are discussed in terms of depth profiles of oxide films calculated from the AR-PES results.
  TRANS TECH PUBLICATIONS LTD, English, Scientific journal
  DOI：https://doi.org/10.4028/www.scientific.net/MSF.483-485.585
  DOI ID：10.4028/www.scientific.net/MSF.483-485.585, ISSN：0255-5476, ORCID：56291594, Web of Science ID：WOS:000228549600137
• Growth of high-quality hexagonal InN on 3C-SiC (001) by molecular beam epitaxy　　　　　　　　　　　　　　　
  H Yaguchi; Y Kitamura; K Nishida; Y Iwahashi; Y Hijikata; S Yoshida
  PHYSICA STATUS SOLIDI C - CONFERENCES AND CRITICAL REVIEWS, VOL 2, NO 7, Volume：2, Number：7, First page：2267, Last page：2270, 2005, [Reviewed]
  We have grown hexagonal InN (h-InN) films on 3C-SiC (001) substrates by RF-N-2 plasma molecular beam epitaxy taking account of small lattice mismatch between h-InN (10-10) and 3C-SiC (110). It was found from X-ray diffraction (XRD) measurements that h-InN grows with h-InN (0001) 11 3C-SiC (001) and h-InN (1-100) vertical bar vertical bar 3C-SiC (110). XRD measurements also revealed that the h-InN epitaxial layers grown on 3C-SiC (001) are composed of single domain. Strong and sharp photoluminescence from the h-InN was clearly observed at around 0.69 eV. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  WILEY-V C H VERLAG GMBH, English, International conference proceedings
  DOI：https://doi.org/10.1002/pssc.200461386
  DOI ID：10.1002/pssc.200461386, ISSN：1862-6351, ORCID：30384820, Web of Science ID：WOS:000230421400058
• Epitaxial growth of hexagonal and cubic InN films　　　　　　　　　　　　　　　
  K. Nishida; Y. Kitamura; Y. Hijikata; H. Yaguchi; S. Yoshida
  Physica Status Solidi (B) Basic Research, Volume：241, Number：12, First page：2839, Last page：2842, Oct. 2004, [Reviewed]
  We have grown InN films on 3C-SiC (001) substrates with and without cubic GaN underlayers by RF-N2 plasma MBE. It was found that, in the case of direct growth on 3C-SiC (001), hexagonal InN grows with the crystal orientation as hexagonal InN (1100)//3C-SiC (110), while, in the case of the growth on cubic GaN underlayers, cubic InN grows with the crystal orientation as cubic InN (110)//cubic GaN (110). Photoluminescence emissions from the cubic and hexagonal InN films were clearly observed at around 0.7 eV. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  International conference proceedings
  DOI：https://doi.org/10.1002/pssb.200405049
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=7444245442&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=7444245442&origin=inward
  DOI ID：10.1002/pssb.200405049, ISSN：0370-1972, ORCID：30384823, SCOPUS ID：7444245442
• Characterization of carrier concentration and mobility in n-type SiC wafers using infrared reflectance spectroscopy　　　　　　　　　　　　　　　
  Katsutoshi Narita; Yasuto Hijikata; Hiroyuki Yaguchi; Sadafumi Yoshida; Shinichi Nakashima
  Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, Volume：43, Number：8 A, First page：5151, Last page：5156, Aug. 2004, [Reviewed]
  We have estimated the free-carrier concentration and drift mobility in n-type 6H-SiC wafers in the carrier concentration range of 10 17-1019 cm3 from far- and mid-infrared (30-2000 cm -1) reflectance spectra obtained at room temperature. A modified classical dielectric function model was employed for the analysis. We found good agreement between the electrical properties derived from infrared reflectance spectroscopy and those derived from Hall effect measurements. We have demonstrated the spatial mapping of carrier concentration and mobility for commercially produced 2 inch SiC wafers.
  INST PURE APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.43.5151
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  DOI ID：10.1143/JJAP.43.5151, ISSN：0021-4922, ORCID：30384821, SCOPUS ID：6444243848, Web of Science ID：WOS:000224841400013
• Characterization of electrical properties in high-dose implanted and post-implantation-annealed 4H-SiC wafers using infrared reflectance spectroscopy　　　　　　　　　　　　　　　
  K Narita; Y Hijikata; H Yaguchi; S Yoshida; J Senzaki; S Nakashima
  SILICON CARBIDE AND RELATED MATERIALS 2003, PRTS 1 AND 2, Volume：457-460, First page：905, Last page：908, 2004, [Reviewed]
  Infrared reflectance spectroscopy has been used to characterize the electrical properties and crystalline damage of high-dose implanted and post-implantation-annealed 4H-SiC. The carrier concentration, mobility and crystalline damage were independently derived from the analysis of the infrared reflectance spectra using the effective medium approximation and the modified dielectric function taking into account the TO and LO phonon damping factors independently. The carrier concentration and mobility in the recrystallized SiC derived from infrared reflectance spectra are in good agreement with those obtained from Hall effect measurements. The annealing temperature dependence of crystalline damage suggests that the impurities are almost activated by the annealing at a temperature as low as 1200degreesC for 30 min, though the crystallinity of the implanted layer is improved with increasing annealing temperature. In addition, it is revealed that the annealing at a temperature as high as 1700degreesC recovers the crystallinity of the implanted layer within I min. These results demonstrate that the infrared reflectance spectroscopy is a useful technique to characterize both the electrical properties and crystalline damage of implanted and post-implantation-annealed layers in SiC wafers simultaneously.
  TRANS TECH PUBLICATIONS LTD, English, Scientific journal
  DOI：https://doi.org/10.4028/www.scientific.net/MSF.457-460.905
  DOI ID：10.4028/www.scientific.net/MSF.457-460.905, ISSN：0255-5476, ORCID：56291630, Web of Science ID：WOS:000222802200215
• Photoemission spectroscopic studies on oxide/SiC interfaces formed by dry and pyrogenic oxidation　　　　　　　　　　　　　　　
  Y Hijikata; H Yaguchi; Y Ishida; M Yoshikawa; T Kamiya; S Yoshida
  SILICON CARBIDE AND RELATED MATERIALS 2003, PRTS 1 AND 2, Volume：457-460, First page：1341, Last page：1344, 2004, [Reviewed]
  The difference in the structure of oxide/SiC interface between dry and pyrogenic oxidation and the effect of post-oxidation annealing in Ar atmosphere on the interfaces have been studied by X-ray and ultraviolet photoelectron spectroscopy to make clear the interface structures which spoil the electrical properties. It is found that intermediate layers containing Si1+ oxidation states exist in both cases of oxidation method and the thickness of the layer changes by Ar annealing. It is also found that the oxide/SiC band offsets and the structures of O2p peak, observed in valence band spectra, change remarkably by Ar POA in both cases of oxidation method. The bond states at SiC/oxide interfaces have been discussed by considering these results together with the results from C-V measurements.
  TRANS TECH PUBLICATIONS LTD, English, Scientific journal
  DOI：https://doi.org/10.4028/www.scientific.net/MSF.457-460.1341
  DOI ID：10.4028/www.scientific.net/MSF.457-460.1341, ISSN：0255-5476, ORCID：48141565, Web of Science ID：WOS:000222802200319
• Spectroscopic ellipsometry study on the dielectric functions of GaPN alloys　　　　　　　　　　　　　　　
  H. Kanaya; H. Yaguchi; Y. Hijikata; S. Yoshida; S. Miyoshi; K. Onabe
  Physica Status Solidi C: Conferences, Volume：0, Number：7, First page：2753, Last page：2756, 2003, [Reviewed]
  We have determined the complex dielectric functions of GaP 1-xNx alloys using spectroscopic ellipsometry to clarify the electronic structure. With increasing N concentration, the E1-gap peak height for both ε1 and ε2 decreases and the E1-gap energy shifts to higher energies, showing that the electronic state at the L point is considerably changed due to the N incorporation. In the lower energy range, a broad peak appears near the fundamental band gap energy of GaP. With increasing N concentration, this peak becomes broader and the peak height increases. This indicates that the band-edge formation in GaP1-xNx alloys is extremely unique compared to that in conventional semiconductor alloys. © 2003 WILEY-VCH Verlag GmbH & Co. KGaA.
  International conference proceedings
  DOI：https://doi.org/10.1002/pssc.200303430
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=33749433192&origin=inward
  DOI ID：10.1002/pssc.200303430, ISSN：1610-1634, ORCID：30384826, SCOPUS ID：33749433192
• Improvement in the luminescence efficiency of GaAsN alloys by photoexcitation　　　　　　　　　　　　　　　
  H Yaguchi; T Morioke; T Aoki; Y Hijikata; S Yoshida; H Akiyama; N Usami; D Aoki; K Onabe
  5TH INTERNATIONAL CONFERENCE ON NITRIDE SEMICONDUCTORS (ICNS-5), PROCEEDINGS, Volume：0, Number：7, First page：2782, Last page：2784, 2003, [Reviewed]
  We found that photoexcitation with high excitation power density at low temperatures improves the luminescence efficiency of GaAsN alloys. From the temporal change of the PL intensity, the improvement occurs in a few minutes. Micro Raman study shows that structural changes occur in the laser-irradiated region. These indicate that the improvement of luminescence properties is due to photoexcitation-induced local structural changes. Since no distinct PL peak shift was observed after the laser irradiation at low temperatures, photoexcitation is a useful technique to improve the luminescence efficiency only. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  WILEY-VCH, INC, English, International conference proceedings
  DOI：https://doi.org/10.1002/pssc.200303514
  DOI ID：10.1002/pssc.200303514, ISSN：1862-6351, ORCID：30384825, Web of Science ID：WOS:000189401700190
• Measurements of the depth profile of the refractive indices in oxide films on SiC by spectroscopic ellipsometry　　　　　　　　　　　　　　　
  Takeshi Iida; Yuichi Tomioka; Kazuo Yoshimoto; Masahiko Midorikawa; Hiroyuki Tukada; Misao Orihara; Yasuto Hijikata; Hiroyuki Yaguchi; Masahito Yoshikawa; Hisayoshi Itoh; Yuuki Ishida; Sadafumi Yoshida
  Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, Volume：41, Number：2 A, First page：800, Last page：804, Feb. 2002, [Reviewed]
  The depth profiles of the refractive indices in thermally oxidized films on SiC have been measured by spectroscopic ellipsometry. Oxide films etched at an angle were used to obtain the depth profiles of the refractive indices in the oxide films. The apparent refractive indices napp and thicknesses have been evaluated, assuming that the films have optically uniform single layer structures. The experimental results show that the values of napp increase with oxide film thickness, and approach the values for oxide films on Si at around 60 nm in thickness. This feature is almost the same as the changes of refractive indices of oxide films with oxidation time reported previously. These results reveal that the oxide films are not optically uniform and that the optical properties change with depth from the surface. It has been found that the film structure model where the oxide film is composed of two layers, a thin interface layer around 1 nm in thickness with a higher refractive index than those of SiC and SiO2 and a stoichiometric SiO2 layer, the thickness of which changes with film thickness, can explain the thickness dependence of napp observed. These results suggest that there exists an interface layer with high refractive indices at oxide film/SiC interfaces.
  JAPAN SOC APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.41.800
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  DOI ID：10.1143/JJAP.41.800, ISSN：0021-4922, ORCID：30384829, SCOPUS ID：0036478462, Web of Science ID：WOS:000176451200070
• Control of macroscopic absorption coefficient of multicrystalline SiGe by microscopic compositional distribution　　　　　　　　　　　　　　　
  Noritaka Usami; Kozo Fujiwara; Toru Ujihara; Gen Sazaki; Hiroyuki Yaguchi; Yoshihiro Murakami; Kazuo Nakajima
  Japanese Journal of Applied Physics, Part 2: Letters, Volume：41, Number：1 A/B, First page：L37, Last page：L39, Jan. 2002, [Reviewed]
  We report on the growth and optical characterizations of multicrystalline SiGe (mc-SiGe) with microscopic compositional distribution for solar cell applications. Mc-SiGe was grown by a simple technique based on the casting method. The compositional distribution and solidification structure of mc-SiGe were found to be strongly dependent on the cooling rate, suggesting that they can be controlled by the growth parameters. Spatial variation of the extinction coefficient, corresponding to the microscopic compositional distribution, was revealed by spectroscopic ellipsometry, and macroscopic optical properties were found to be controlled by the microscopic compositional distribution. The advantage of mc-SiGe was further revealed by the increased absorption in the lower energies compared with uniform SiGe with almost the same average composition.
  INST PURE APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.41.L37
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0037082098&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0037082098&origin=inward
  DOI ID：10.1143/JJAP.41.L37, ISSN：0021-4922, ORCID：30384828, SCOPUS ID：0037082098, Web of Science ID：WOS:000173882600012
• Spatial mapping of the carrier concentration and mobility in SiC wafers by micro fourier-transform infrared spectroscopy　　　　　　　　　　　　　　　
  H. Yaguchi; K. Narita; Y. Hijikata; S. Yoshida; S. Nakashima; N. Oyanagi
  Materials Science Forum, Volume：389-393, Number：1, First page：621, Last page：624, 2002, [Reviewed]
  Micro Fourier-transform infrared (FTIR) spectroscopy has been used to investigate the spatial distribution of the carrier concentration and mobility in SiC wafers. The carrier concentration and mobility were independently derived from the reflectance spectra based on the dielectric function taking into account the effect of phonons and plasmons. The carrier concentration profile obtained for an intentionally inhomogeneous N-doped 6H-SiC wafer coincides well with the spatial distribution of color in the wafer. For commercially available wafers, carrier concentrations are found to increase with approaching the center of the wafers. These results demonstrate that micro FTIR is a nondestructive and noncontact technique to spatially characterize the carrier concentration and mobility in SiC wafers. © 2002 Trans Tech Publications.
  Scientific journal
  DOI：https://doi.org/10.4028/www.scientific.net/msf.389-393.621
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=34247249828&origin=inward
  DOI ID：10.4028/www.scientific.net/msf.389-393.621, ISSN：0255-5476, eISSN：1662-9752, SCOPUS ID：34247249828
• X-ray photoelectron spectroscopy studies of post-oxidation process effects on oxide/SiC interfaces　　　　　　　　　　　　　　　
  Y Hijikata; H Yaguchi; M Yoshikawa; S Yoshida
  SILICON CARBIDE AND RELATED MATERIALS 2001, PTS 1 AND 2, PROCEEDINGS, Volume：389-3, First page：1033, Last page：1036, 2002, [Reviewed]
  In this report, we carried out x-ray photoclectron spectroscopy measurements on slope shaped oxide films to explore the changes of interfacial structures by post oxidation processes. By the observation of Si2p, C1s and O1s spectra, the bonding states which influence the electrical properties of MOS structures were suggested to be bonds related to carbon. We also discuss the reasons for the improvement of MOS properties by these post oxidation processes.
  TRANS TECH PUBLICATIONS LTD, English, Scientific journal
  DOI：https://doi.org/10.4028/www.scientific.net/MSF.389-393.1033
  DOI ID：10.4028/www.scientific.net/MSF.389-393.1033, ISSN：0255-5476, ORCID：48141540, Web of Science ID：WOS:000177321100249
• Characterization of the interfaces between SiC and oxide films by spectroscopic ellipsometry　　　　　　　　　　　　　　　
  Y Tomioka; T Iida; M Midorikawa; H Tukada; K Yoshimoto; Y Hijikata; H Yaguchi; M Yoshikawa; Y Ishida; R Kosugi; S Yoshida
  SILICON CARBIDE AND RELATED MATERIALS 2001, PTS 1 AND 2, PROCEEDINGS, Volume：389-3, First page：1029, Last page：1032, 2002, [Reviewed]
  Spectroscopic ellipsometry has been used to investigate, for the first time, the optical properties of oxide films on SiC to discuss the difference of the structures of SiC/SiO2 interfaces with oxidation processes, thermal oxidation in dry oxygen, pyrogenic oxidation and low temperature deposition of oxides by chemical vapor deposition. It was found that there exist interface layers with high refractive indices between SiC and SiO2, the values of which are larger than those of SiC and SiO2 and depend on the oxidation process. The validity of the evaluation of refractive indices of the interfaces has also been discussed.
  TRANS TECH PUBLICATIONS LTD, English, Scientific journal
  DOI：https://doi.org/10.4028/www.scientific.net/MSF.389-393.1029
  DOI ID：10.4028/www.scientific.net/MSF.389-393.1029, ISSN：0255-5476, ORCID：56291595, Web of Science ID：WOS:000177321100248
• Composition analysis of SiO2/SiC interfaces by electron spectroscopic measurements using slope-shaped oxide films　　　　　　　　　　　　　　　
  Y Hijikata; H Yaguchi; M Yoshikawa; S Yoshida
  APPLIED SURFACE SCIENCE, Volume：184, Number：1-4, First page：161, Last page：166, Dec. 2001, [Reviewed]
  We have characterized SiO2/SiC interfaces by X-ray photoelectron spectroscopy in terms of composition and bonds to clarify the reasons for the problems in silicon carbide metal-oxide-semiconductor field-effect-transistor and MOS structures. The oxide films on 6H-SiC were shaped into slopes by HF chemical etching to obtain the depth profile of the composition and the bondings. An interface layer was found near the SiO2/SiC boundary, where SiO2 stoichiometry is collapsed and there exists the bondings other than Si-O-2 and Si-C. Also, we revealed the differences in the interface properties for different oxidation processes. (C) 2001 Elsevier Science B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/S0169-4332(01)00491-3
  DOI ID：10.1016/S0169-4332(01)00491-3, ISSN：0169-4332, eISSN：1873-5584, CiNii Articles ID：80012788973, ORCID：56291762, Web of Science ID：WOS:000173000100027
• Spectroscopic ellipsometry study on the electronic structure near the absorption edge of GaAsN alloys　　　　　　　　　　　　　　　
  H. Yaguchi; S. Matsumoto; Y. Hijikata; S. Yoshida; T. Maeda; M. Ogura; D. Aoki; K. Onabe
  Physica Status Solidi (B) Basic Research, Volume：228, Number：1, First page：269, Last page：272, Nov. 2001, [Reviewed]
  Spectroscopic ellipsometry has been used to investigate the electronic structure near the fundamental absorption edge of GaAsN alloys grown by metalorganic vapor phase epitaxy. The fundamental absorption edge is clearly observed in the imaginary part of the dielectric function and shifts to lower energies with increasing N concentration. In addition, the absorption structure is observed near the E0 gap energy of GaAs even in GaAsN alloys. This unequivocally shows that the fundamental absorption edge of GaAsN is not shifted from the E0 gap of GaAs but newly formed by the N incorporation. Thus, the formation of the narrowest band gap of GaAsN alloys is found to be completely different from that of conventional compound semiconductor alloys, such as AIGaAs and GaAsP.
  WILEY-V C H VERLAG GMBH, English, Scientific journal
  DOI：https://doi.org/10.1002/1521-3951(200111)228:1<269::AID-PSSB269>3.0.CO;2-3
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0035541085&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0035541085&origin=inward
  DOI ID：10.1002/1521-3951(200111)228:1<269::AID-PSSB269>3.0.CO;2-3, ISSN：0370-1972, ORCID：30384834, SCOPUS ID：0035541085, Web of Science ID：WOS:000172513100060
• Photoluminescence study on temperature dependence of band gap energy of GaAsN alloys　　　　　　　　　　　　　　　
  H. Yaguchi; S. Kikuchi; Y. Hijikata; S. Yoshida; D. Aoki; K. Onabe
  Physica Status Solidi (B) Basic Research, Volume：228, Number：1, First page：273, Last page：277, Nov. 2001, [Reviewed]
  We have studied the temperature dependence of photoluminescence (PL) spectra of GaAsN alloys. The PL peak energy shift due to the temperature change decreases with increasing N concentration of GaAsN alloys. The localized state emission partly contributes to the decrease in the PL peak energy shift. In addition, the small PL peak energy shift at high temperatures is due to the reduction in the temperature dependence of the band gap energy. From the analysis using the Bose-Einstein statistical expression, the average phonon energy is much larger than that expected from the linear interpolation between GaAs and GaN, indicating that the interaction between electrons and phonons localized at N atoms plays an important role in the reduction of the temperature dependence of the band gap energy of GaAsN alloys.
  WILEY-V C H VERLAG GMBH, English, Scientific journal
  DOI：https://doi.org/10.1002/1521-3951(200111)228:1<273::AID-PSSB273>3.0.CO;2-N
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0035541092&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0035541092&origin=inward
  DOI ID：10.1002/1521-3951(200111)228:1<273::AID-PSSB273>3.0.CO;2-N, ISSN：0370-1972, ORCID：30384833, SCOPUS ID：0035541092, Web of Science ID：WOS:000172513100061
• Temperature dependence of excitonic Gamma(c)-Gamma(v) transition energies GaxIn1-xP crystals　　　　　　　　　　　　　　　
  Y Ishitani; H Yaguchi; Y Shiraki
  JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, Volume：40, Number：3A, First page：1183, Last page：1187, Mar. 2001, [Reviewed]
  The excitonic Gamma (c)-Gamma (v) transition energies of disordered GaxIn1-xP (x = 0.0, 0.52, 0.70, and 1.0) crystals have been measured by photoreflectance (PR) measurements at temperatures from 20 to 300 K. The photoluminescence (PL) peak energy at 20 K is found to be lower than the energy obtained from PR or photoluminescence excitation (PLE) spectra by about 6 meV. The temperature dependence of the transition energy is expressed by a function consisting of several terms, each of which represents the effect of the volume-thermal expansion or the electron-phonon interaction. It is found that the temperature-dependent decrease of the transition energy from the pure electronic transition energy is mainly caused by the electron-phonon interaction. The energy shift due to the electron-phonon interaction increases as the Gap mole fraction increases.
  INST PURE APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.40.1183
  DOI ID：10.1143/JJAP.40.1183, ISSN：0021-4922, ORCID：30384835, Web of Science ID：WOS:000170771500006
• Optical characterization of metalorganic vapor-phase epitaxy-grown GaAs1-xNx alloys using spectroscopic ellipsometry　　　　　　　　　　　　　　　
  S Matsumoto; H Yaguchi; S Kashiwase; T Hashimoto; S Yoshida; D Aoki; K Onabe
  JOURNAL OF CRYSTAL GROWTH, Volume：221, First page：481, Last page：484, Dec. 2000, [Reviewed]
  We have measured complex dielectric functions, epsilon (1) + i epsilon (2), of GaAs1-xNx alloys using spectroscopic ellipsometry to investigate higher-energy band gaps. The E-1 gap-related peak height for epsilon (2) decreases with increasing N concentration, indicating that the optical absorption at the E-1 gap decreases. On the contrary, the E-2 gap transition does not change so much with varying N concentration. These results are consistent with the theoretical study, which predicts that the lowest conduction band is mostly a combination of the Gamma and L states. The bowing parameters of the E-1 and E-2 yaps are rather large but much smaller than the bowing parameter of the E-o gap. (C) 2000 Elsevier Science B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/S0022-0248(00)00748-X
  DOI ID：10.1016/S0022-0248(00)00748-X, ISSN：0022-0248, CiNii Articles ID：80012169205, ORCID：30384838, Web of Science ID：WOS:000166501400085
• Characterization of oxide films on SiC by spectroscopic ellipsometry　　　　　　　　　　　　　　　
  T Iida; Y Tomioka; Y Hijikata; H Yaguchi; M Yoshikawa; Y Ishida; H Okumura; S Yoshida
  JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS, Volume：39, Number：10B, First page：L1054, Last page：L1056, Oct. 2000, [Reviewed]
  We have, for the first time. evaluated the optical constants of thermally oxidized films on SIC by spectroscopic ellipsometry, and discussed the characteristics of SiC/SiO2 interfaces. It was found that the effective refractive indices are smaller than those of the oxide films on Si. They increase with oxidation time, or oxide thickness, reaching to the values of Si oxides. The refractive indices also depend on the oxidation methods, and the pyrogenic oxidation brings about larger refractive indices than dry oxidation. The origin of the small refractive indices of oxide films on SiC was discussed in terms of interface structures and composition in comparison with those of oxide films on Si.
  INST PURE APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.39.L1054
  DOI ID：10.1143/JJAP.39.L1054, ISSN：0021-4922, ORCID：30384836, Web of Science ID：WOS:000090138800014
• Optical properties of cubic GaN grown on 3C-SiC (100) substrates by metalorganic vapor phase epitaxy　　　　　　　　　　　　　　　
  J. Wu; H. Yaguchi; B. P. Zhang; Y. Segawa; K. Onabe; Y. Shiraki
  Physica Status Solidi (A) Applied Research, Volume：180, Number：1, First page：403, Last page：407, Jul. 2000, [Reviewed]
  Cubic GaN with different low-temperature buffer layers were grown on 3C-SiC (100) substrates by metalorganic vapor phase epitaxy (MOVPE). The sample surface morphology was affected considerably by the thickness of the buffer layer. An X-ray diffraction-peak shift was observed for these samples, indicating the existence of residual strain inside the crystal. The origin of the residual strain can be attributed to the different thermal expansion coefficients of GaN and 3C-SiC. The residual strain has a strong influence on the excitonic transition energies. From the strain dependence of the shift of the exciton peaks, the value of the excitonic bandgap and the strain coefficient (relation between strain parallel to z-axis and exciton energy) of cubic GaN were estimated.
  WILEY-V C H VERLAG GMBH, English, Scientific journal
  DOI：https://doi.org/10.1002/1521-396X(200007)180:1<403::AID-PSSA403>3.0.CO;2-A
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0034224763&origin=inward
  DOI ID：10.1002/1521-396X(200007)180:1<403::AID-PSSA403>3.0.CO;2-A, ISSN：0031-8965, ORCID：30384840, SCOPUS ID：0034224763, Web of Science ID：WOS:000088605900067
• Fabrication and optical properties of GaAs/AlGaAs quantum dot grown in tetrahedral-shaped recesses on GaAs (111)B substrates by MOVPE　　　　　　　　　　　　　　　
  T Tsujikawa; S Mori; H Watanabe; M Yoshita; H Akiyama; R van Dalen; K Onabe; H Yaguchi; Y Shiraki; R Ito
  PHYSICA E, Volume：7, Number：3-4, First page：308, Last page：316, May 2000, [Reviewed]
  GaAs/AlGaAs quantum dots were grown in tetrahedral-shaped recesses (TSRs) on GaAs ((1) over bar (1) over bar (1) over bar)B substrates at 850 degrees C by metalorganic vapor-phase epitaxy on the bottom ((1) over bar (1) over bar (1) over bar)B regions of the TSRs. As the AlGaAs barrier layer became thicker, a trench-like region comprised of {1 1 (2) over bar} and {(1) over bar (1) over bar 2} vertical sidewalls formed at the bottom region of the TSR. A 780 Angstrom-wide and 96 Angstrom-thick GaAs quantum dot was formed at the bottom of the trench-like region. The luminescence from GaAs layer at only the ((1) over bar (1) over bar (1) over bar)B bottom region of the TSR was confirmed by cathodoluminescence image observation. By micro-photoluminescence observation a narrow line from the bottom region was observed at 1.5511 eV and the luminescence from higher-energy states was observed. The calculation for a 780 Angstrom x 780 Angstrom x 96 Angstrom quantum box revealed that these energy states reflected both the lateral and vertical quantum confinements. (C) 2000 Elsevier Science B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/S1386-9477(99)00331-8
  DOI ID：10.1016/S1386-9477(99)00331-8, ISSN：1386-9477, ORCID：56291692, Web of Science ID：WOS:000087358100003
• Second-harmonic generation from GaP/AlP multilayers on GaP (111) substrates based on quasi-phase matching for the fundamental standing wave　　　　　　　　　　　　　　　
  M Sato; H Yaguchi; Shoji, I; K Onabe; R Ito; Y Shiraki; S Nakagawa; N Yamada
  JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS, Volume：39, Number：4B, First page：L334, Last page：L336, Apr. 2000, [Reviewed]
  We have demonstrated second-harmonic generation (SHG) from GaP/AIP multilayers an GaP(111)A substrates based on quasi-phase matching (QPM) for the fundamental standing wave. Theoretical calculation predicted that the SWG power increases with increasing number of GaP/AIP multilayers because of their small absorption coefficient in the spectral range of second-harmonic light, which is in contrast to the case of GaAs/AlAs QPM multilayers. In the transmission SHG measurement using a frequency-tunable Ti:Sapphire laser as a fundamental wave source, maximum SWG power was obtained at a fundamental wavelength of 990 nm from the five-pair GaP/AIP QPM multilayers. The wavelength conversion efficiency was measured to be 9.8 x 10(-10)%/W, which was smaller than the theoretical value of 6.5 x 10(-8)%/W.
  JAPAN J APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.39.L334
  DOI ID：10.1143/JJAP.39.L334, ISSN：0021-4922, ORCID：30384841, Web of Science ID：WOS:000088910900003
• Optical constants of cubic GaN, AlN, and AlGaN alloys　　　　　　　　　　　　　　　
  Takanobu Suzuki; Hiroyuki Yaguchi; Hajime Okumura; Yuuki Ishida; Sadafumi Yoshida
  Japanese Journal of Applied Physics, Part 2: Letters, Volume：39, Number：6 A, First page：L497, Last page：L499, 2000, [Reviewed]
  We have used spectroscopic ellipsometry to investigate, for the first time, the optical constants of cubic GaN, AlN, and AlGaN alloy epitaxial layers grown by molecular beam epitaxy. The refractive indices of cubic AlGaN were found to decrease with increasing Al content, as expected from the empirical observation that the refractive index decreases with increasing direct bandgap energy. In the transparent wavelength region, the refractive indices of cubic AlGaN with lower Al contents are somewhat larger than those of hexagonal modifications, while with higher Al contents, the refractive indices of cubic AlGaN and hexagonal AlGaN are almost equal. We also found that the direct bandgap energies of cubic AlGaN show a parabolic dependence on the Al content.
  JAPAN J APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.39.L497
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0033702328&origin=inward
  DOI ID：10.1143/JJAP.39.L497, ISSN：0021-4922, ORCID：30384839, SCOPUS ID：0033702328, Web of Science ID：WOS:000088911300005
• Time-resolved photoluminescence of cubic GaN grown by metalorganic vapor phase epitaxy　　　　　　　　　　　　　　　
  H. Yaguchi; J. Wu; H. Akiyama; M. Baba; K. Onabe; Y. Shiraki
  Physica Status Solidi (B) Basic Research, Volume：216, Number：1, First page：237, Last page：240, Nov. 1999, [Reviewed]
  Time-resolved photoluminescence of high quality cubic GaN was measured to clarify the origin of the emissions observed in cubic GaN. The 3.27 eV emission decay was fast and the intensity decreased with a lifetime of 260 ps at early decay and with a lifetime of 900 ps afterwards. The decay of the 3.18 eV emission was much slower than that of the 3.27 eV emission and the lifetime was 3.8 ns. In time-resolved spectra, the 3.18 eV emission had a broadening on the high-energy side at early times and the peak moved to lower energies with increasing time. These results can be explained in terms of the model for a donor-acceptor pair transition.
  WILEY-V C H VERLAG GMBH, English, Scientific journal
  DOI：https://doi.org/10.1002/(SICI)1521-3951(199911)216:1<237::AID-PSSB237>3.0.CO;2-O
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0033242881&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0033242881&origin=inward
  DOI ID：10.1002/(SICI)1521-3951(199911)216:1<237::AID-PSSB237>3.0.CO;2-O, ISSN：0370-1972, ORCID：30384850, SCOPUS ID：0033242881, Web of Science ID：WOS:000084193900046
• Substrate misorientation dependence of the hexagonal phase inclusion in cubic GaN films grown by metalorganic vapor phase epitaxy　　　　　　　　　　　　　　　
  A. Nagayama; R. Katayama; N. Nakadan; K. Miwa; H. Yaguchi; J. Wu; K. Onabe; Y. Shiraki
  Physica Status Solidi (A) Applied Research, Volume：176, Number：1, First page：513, Last page：517, Nov. 1999, [Reviewed]
  The metalorganic vapor phase epitaxial (MOVPE) growth of cubic GaN layers on misoriented GaAs (001) substrates, the faces of which were tilted from (001) toward [11̄0] or [110] by 4°, was performed in order to investigate the effect of the substrate misorientation on the inclusion of hexagonal phase in the cubic GaN layer. The sample grown on the tilted surface toward [11̄0] showed an enhanced generation of the hexagonal domain on the (11̄1) face, whereas the hexagonal domain on the (1̄11) face was suppressed. The sample grown on the tilted surface toward [110] showed the generation of the hexagonal domains on both the (11̄1) and (1̄11) faces with an equal magnitude. It is suggested that the generation of hexagonal domains may be suppressed when the exposure of the (11̄1) or (1̄11) faces by the thermal damage of the substrate surface is reduced.
  WILEY-V C H VERLAG GMBH, English, Scientific journal
  DOI：https://doi.org/10.1002/(SICI)1521-396X(199911)176:1<513::AID-PSSA513>3.0.CO;2-Y
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0033221287&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0033221287&origin=inward
  DOI ID：10.1002/(SICI)1521-396X(199911)176:1<513::AID-PSSA513>3.0.CO;2-Y, ISSN：0031-8965, ORCID：30384849, SCOPUS ID：0033221287, Web of Science ID：WOS:000084032200098
• Selective growth of cubic GaN an patterned GaAs(100) substrates by metalorganic vapor phase epitaxy　　　　　　　　　　　　　　　
  J Wu; M Kudo; A Nagayama; H Yaguchi; K Onabe; Y Shiraki
  PHYSICA STATUS SOLIDI A-APPLIED RESEARCH, Volume：176, Number：1, First page：557, Last page：560, Nov. 1999, [Reviewed]
  Selective growth of cubic GaN on patterned GaAs substrates was studied. The structural and morphological properties of cubic GaN are very dependent on the orientation of the mask stripes. Tn the case of window stripe opening along [011] direction, (111)B facets were clearly observed in all the samples, regardless of the different growth time. Both X-ray diffraction and photoluminescence measurements showed that the hexagonal phase GaN was considerably incorporated in the cubic GaN layer, indicating that the hexagonal GaN is easily constructed along-the (111)B facet. In contrast, window stripes opening along [01-1] direction resulted in the:formation of (311)A facets and subsequently a relatively flat surface occurred as the growth proceeded.-Strong emission peaks of cubic GaN were observed in the photoluminescence spectra.
  WILEY-V C H VERLAG GMBH, English, Scientific journal
  DOI：https://doi.org/10.1002/(SICI)1521-396X(199911)176:1<557::AID-PSSA557>3.0.CO;2-2
  DOI ID：10.1002/(SICI)1521-396X(199911)176:1<557::AID-PSSA557>3.0.CO;2-2, ISSN：0031-8965, ORCID：30384847, Web of Science ID：WOS:000084032200105
• Optical characterization of cubic AlGaN epilayers by cathodoluminescence and spectroscopic ellipsometry　　　　　　　　　　　　　　　
  H Okumura; T Koizumi; Y Ishida; H Yaguchi; S Yoshida
  PHYSICA STATUS SOLIDI B-BASIC RESEARCH, Volume：216, Number：1, First page：211, Last page：214, Nov. 1999, [Reviewed]
  Cubic AlGaN epilayers grown by molecular beam epitaxy were characterized by cathodoluminescence and spectroscopic ellipsometry techniques. The linear increase of the bandgap energy versus Al composition was consistently confirmed by the two techniques, which indicate the direct transition nature of cubic AlGaN band structure. The energy dependence of optical constants for cubic GaN was also obtained by the simulation of the measured allipsometric data.
  WILEY-V C H VERLAG GMBH, English, Scientific journal
  DOI：https://doi.org/10.1002/(SICI)1521-3951(199911)216:1<211::AID-PSSB211>3.3.CO;2-A
  DOI ID：10.1002/(SICI)1521-3951(199911)216:1<211::AID-PSSB211>3.3.CO;2-A, ISSN：0370-1972, ORCID：30384844, Web of Science ID：WOS:000084193900041
• MOVPE growth and luminescence properties of GaAsN alloys with higher nitrogen concentrations　　　　　　　　　　　　　　　
  K Onabe; D Aoki; J Wu; H Yaguchi; Y Shiraki
  PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE, Volume：176, Number：1, First page：231, Last page：235, Nov. 1999, [Reviewed]
  Highly luminescent GaAsN alloy films have been successfully obtained with N concentrations up to 3.1% by metalorganic vapor phase epitaxy (MOVPE). The band-gap bowing parameter estimated from the photoluminescence (PL) peak energy is not constant but dependent on the N concentration; 24.0 eV for N < 1% and 17.0 eV for N > 1% at 20 KI and 22.4 eV: for N < 1% and 14.5 eV for N >1% at room temperature. From the characteristic features of the luminescence properties, the: band-edge states are found to be much localized below the conduction band edge, and the emission process at low temperatures is associated with these localized states as in GaPN alloys.
  WILEY-V C H VERLAG GMBH, English, Scientific journal
  DOI：https://doi.org/10.1002/(SICI)1521-396X(199911)176:1<231::AID-PSSA231>3.0.CO;2-9
  DOI ID：10.1002/(SICI)1521-396X(199911)176:1<231::AID-PSSA231>3.0.CO;2-9, ISSN：1862-6300, eISSN：1862-6319, ORCID：30384843, Web of Science ID：WOS:000084032200044
• Stimulated emission from optically pumped cubic GaN/AlGaN double heterostructures　　　　　　　　　　　　　　　
  Jun Wu; Hiroyuki Yaguchi; Kentaro Onabe; Yasuhiro Shiraki
  Journal of Crystal Growth, Volume：197, Number：1-2, First page：73, Last page：77, 1999, [Reviewed]
  Cubic GaN/AlGaN heterostructures were grown on semi-insulating GaAs(I 0 0) substrates by metalorganic vaporphase epitaxy. Optical pumping experiments were performed on cubic GaN/AlGaN cavities, which were formed simply by cleaving the substrate. Strong stimulated emission at a wavelength of 394 nm was observed from the cleaved edge of the optically pumped cubic GaN/AlGaN heterostructures at 15 K. The stimulated emission was demonstrated by the superlinear increase of the output intensity and the highly TE-polarized nature. Besides this strong stimulated emission, an additional stimulated emission centered at 383 nm is also observed from some samples. © 1999 Elsevier Science B.V. All rights reserved.
  Scientific journal
  DOI：https://doi.org/10.1016/S0022-0248(98)00945-2
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0033079425&origin=inward
  DOI ID：10.1016/S0022-0248(98)00945-2, ISSN：0022-0248, CiNii Articles ID：80010901748, ORCID：48141822, SCOPUS ID：0033079425
• Photoluminescence study of InP/GaP highly strained quantum wells
  T. Kimura; H. Yaguchi; N. Usami; K. Onabe; Y. Shiraki
  Institute of Physics Conference Series, Volume：162, First page：511, Last page：516, 1999
  Scientific journal
  ORCID：56291592, Web of Science ID：WOS:000177562700083
• Quantum size effect of lead iodide nanoparticles formed by a Langmuir-Blodgett technique　　　　　　　　　　　　　　　
  Tetsuya Yamaki; Keisuke Asai; Kenkichi Ishigure; Kazuhiro Ema; Hiroyuki Yaguchi
  Molecular Crystals and Liquid Crystals Science and Technology Section A: Molecular Crystals and Liquid Crystals, Volume：337, First page：225, Last page：228, 1999, [Reviewed]
  Nanoparticles of lead iodide (PbI2) were prepared by exposure of Langmuir-Blodgett (LB) films of lead arachidate to hydrogen iodide. The photoluminescence (PL) spectrum of the nanoparticles consisted of three bands: an exciton band and two low-energy bands associated with stoichiometric and structural defects. The center of the exciton band was blue-shifted due to a quantum size effect. The PL spectra drastically changed when the temperature increased. © 1999 OPA (Overseas Publishers Association) N.V. Published by license under the Gordon and Breach Science Publishers imprint.
  GORDON BREACH SCI PUBL LTD, English, Scientific journal
  DOI：https://doi.org/10.1080/10587259908023418
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=33745440831&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=33745440831&origin=inward
  DOI ID：10.1080/10587259908023418, ISSN：1058-725X, ORCID：56291741, SCOPUS ID：33745440831, Web of Science ID：WOS:000084232500054
• High-Temperature Metalorganic Vapor Phase Epitaxial Growth of GaAs/AlGaAs Quantum Structures in Tetrahedral-Shaped Recesses on GaAs (111)B Substrates　　　　　　　　　　　　　　　
  Tomoko Tsujikawa; Toshifumi Irisawa; Hiroyuki Yaguchi; Kentaro Onabe; Yasuhiro Shiraki; Ryoichi Ito
  Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, Volume：38, Number：1 B, First page：459, Last page：464, 1999, [Reviewed]
  GaAs/AlGaAs quantum structures were grown in tetrahedral-shaped recesses (TSRs) on GaAs {1̄1̄1̄}B substrates at temperatures above 800°C by metalorganic vapor phase epitaxy because quantum dots were expected to be formed at the bottom {1̄1̄1̄} regions of the TSRs. Observation of cathodoluminescence revealed that GaAs quantum structures with different layer thicknesses were formed at {1̄00} edge regions, {1̄1̄0} and {11̄1̄}A sidewalls and the {1̄1̄1̄} bottom and surface regions of the TSR. Growth on the (1̄1̄1̄)B surface region between TSRs was clearly observed for the sample grown at 850°C. As the growth temperature was raised above 850°C, the photoluminescence intensity on the {1̄1̄1̄}B surface increased whereas that on the {001̄} edge regions and {11̄1̄}A sidewall regions decreased. With an increase in well thickness, the luminescence from the bottom and edge regions was simultaneously observed. A 50 A-thick quantum well was formed on the small bottom region. From scanning electron microscope observation, the lateral size of the region was 550 Å.
  JAPAN J APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.38.459
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0032621849&origin=inward
  DOI ID：10.1143/JJAP.38.459, ISSN：0021-4922, ORCID：30384842, SCOPUS ID：0032621849, Web of Science ID：WOS:000078971100039
• Photoluminescence and photoluminescence-excitation spectroscopy of GaPAsN/GaP lattice-matched multiple quantum well structures　　　　　　　　　　　　　　　
  Goshi Biwa; Hiroyuki Yaguchi; Kentaro Onabe; Yasuhiro Shiraki
  Journal of Crystal Growth, Volume：195, Number：1-4, First page：574, Last page：578, Dec. 1998, [Reviewed]
  GaP1-x-yAsyNx/GaP (x = 2.0%, y = 12%) lattice-matched multiple quantum well (MQW) structures have been grown by metalorganic vapor-phase epitaxy (MOVPE). Low-temperature photoluminescence (PL) and photoluminescence excitation (PLE) measurements for the varied well widths (Lz = 36, 24, and 16 Å) have revealed that the quantum confinement effect to the well manifests itself only in the narrow wells whose width is comparable with or shorter than the spatial extent of the localized excitons. Higher-temperature luminescence has been drastically enhanced, where the room temperature PL intensity is estimated 103-104 times larger than in the bulk. This is due to the efficient electron confinement to the well which is brought about by the large conduction band offset ΔEc (∼280 meV). © 1998 Elsevier Science B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/S0022-0248(98)00734-9
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0032477147&origin=inward
  DOI ID：10.1016/S0022-0248(98)00734-9, ISSN：0022-0248, ORCID：56291728, SCOPUS ID：0032477147, Web of Science ID：WOS:000077839200092
• Micro Raman and micro photoluminescence study of cubic GaN grown on 3C-SiC(0 0 1) substrates by metalorganic vapor phase epitaxy　　　　　　　　　　　　　　　
  Hiroyuki Yaguchi; Jun Wu; Baoping Zhang; Yusaburo Segawa; Hiroyuki Nagasawa; Kentaro Onabe; Yasuhiro Shiraki
  Journal of Crystal Growth, Volume：195, Number：1-4, First page：323, Last page：327, Dec. 1998, [Reviewed]
  We have investigated metalorganic vapor phase epitaxy-grown GaN grains on a 3C-SiC(0 0 1) substrate using micro Raman and micro photoluminescence spectroscopy. Polarized micro Raman spectra clearly showed that horizontal flat facets and inclined facets of the rectangular GaN grains correspond to cubic phase regions and hexagonal phase regions, respectively. To examine the photoluminescence properties of "pure" cubic GaN, micro photoluminescence was performed by focusing a laser beam on the horizontal flat facet. A strong photoluminescence line with the full-width at half-maximum of 5 meV was observed, which is the smallest value to date and shows that the crystal quality of the cubic phase region is excellent. We could clearly identify free exciton, donor bound exciton and acceptor bound exciton emissions in the cubic GaN. © 1998 Elsevier Science B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/S0022-0248(98)00672-1
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0032477174&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0032477174&origin=inward
  DOI ID：10.1016/S0022-0248(98)00672-1, ISSN：0022-0248, ORCID：56291747, SCOPUS ID：0032477174, Web of Science ID：WOS:000077839200055
• Sublattice reversal in GaAs/Si/GaAs (100) heterostructures by molecular beam epitaxy　　　　　　　　　　　　　　　
  Shinji Koh; Takashi Kondo; Tetsuya Ishiwada; Chihiro Iwamoto; Hideki Ichinose; Hiroyuki Yaguchi; Takanori Usami; Yasuhiro Shiraki; Ryoichi Ito
  Japanese Journal of Applied Physics, Part 2: Letters, Volume：37, Number：12 SUPPL. B, First page：L1493, Last page：L1496, Dec. 1998, [Reviewed]
  Sublattice reversal in III-V compound semiconductors grown on group-IV epitaxial layers on III-V substrates has been proposed for fabricating nonlinear optical devices with domain-inverted compound semiconductor structures. Sublattice reversal epitaxy is demonstrated in the GaAs/Si/GaAs (100) system and confirmed by reflection high energy electron diffraction, cross-sectional transmission electron microscopy, anisotropic etching, and optical second-harmonic generation measurements. The present sublattice reversal seems to be assisted by self annihilation of antiphase domains generated at GaAs/Si interfaces.
  JAPAN J APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.37.L1493
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0032295743&origin=inward
  DOI ID：10.1143/JJAP.37.L1493, ISSN：0021-4922, ORCID：30384870, SCOPUS ID：0032295743, Web of Science ID：WOS:000078189800001
• Polarization characteristics of crescent-shaped tensile-strained GaAsP/AlGaAs quantum wire-like lasers (vol 37, pg 1556, 1998)　　　　　　　　　　　　　　　
  M Ishikawa; W Pan; Y Kaneko; H Yaguchi; K Onabe; R Ito; Y Shiraki
  JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, Volume：37, Number：7, First page：4230, Last page：4230, Jul. 1998, [Reviewed]
  JAPAN J APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.37.4230
  DOI ID：10.1143/JJAP.37.4230, ISSN：0021-4922, ORCID：30384868, Web of Science ID：WOS:000075363300072
• Theoretical study of conduction band edge formation in GaP1 - XNx alloys using a tight-binding approximation　　　　　　　　　　　　　　　
  H. Yaguchi
  Journal of Crystal Growth, Volume：189-190, First page：500, Last page：504, Jun. 1998, [Reviewed]
  The conduction band edge formation in GaP1 - xNx alloys is theoretically studied using a tight-binding method. The electronic structure of GaP1 - xNx ordered alloys whose units-cell size is a × a × na (n = 1-5) is calculated. The calculation confirmed that the conduction band edge formation in Ga1 - xNx alloys originates from the formation of the A line. Localization at the N atoms is also discussed. © 1998 Elsevier Science B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/S0022-0248(98)00339-X
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0032090874&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0032090874&origin=inward
  DOI ID：10.1016/S0022-0248(98)00339-X, ISSN：0022-0248, ORCID：48141882, SCOPUS ID：0032090874, Web of Science ID：WOS:000074730400102
• Temperature dependence of photoluminescence of GaP1-xNx alloys　　　　　　　　　　　　　　　
  Hiroyuki Yaguchi; Goshi Biwa; Seiro Miyoshi; Daiichiro Aoki; Keisuke Arimoto; Kentaro Onabe; Ryoichi Ito; Yasuhiro Shiraki
  Journal of Crystal Growth, Volume：189-190, First page：496, Last page：499, Jun. 1998, [Reviewed]
  We report on the temperature dependence of photoluminescence (PL) in GaP1-xNx alloys. With increasing temperature the feature of the PL spectrum changes considerably and the luminescence with lower energies becomes predominant. This is explained by thermal activation processes from localized states to the state where excitons can move freely. By estimating the activation energies from the temperature dependence of the PL intensity, it is found that the state where excitons can move freely is formed below the band edge of GaP and shifts to lower energies with increasing nitrogen content. This state is considered to originate from the isoelectronic trap due to isolated nitrogens in GaP (A line) and correspond to the band edge of the GaP1-xNx alloy system. © 1998 Elsevier Science B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/S0022-0248(98)00338-8
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0032092389&origin=inward
  DOI ID：10.1016/S0022-0248(98)00338-8, ISSN：0022-0248, ORCID：30384871, SCOPUS ID：0032092389, Web of Science ID：WOS:000074730400101
• Metalorganic vapor-phase epitaxy of GaP1-x-yAsyNx quaternary alloys on GaP　　　　　　　　　　　　　　　
  Goshi Biwa; Hiroyuki Yaguchi; Kentaro Onabe; Yasuhiro Shiraki
  Journal of Crystal Growth, Volume：189-190, First page：485, Last page：489, Jun. 1998, [Reviewed]
  We report on a successful growth of GaP1-x-yAsyNx quaternary alloys on GaP by metalorganic vapor-phase epitaxy (MOVPE). The arsenic solid composition increases with increasing AsH3 supply during the MOVPE growth, while the nitrogen composition is unchanged. The alloys with compositions (x ∼ 2.3%, 0 < y < 19%) are obtained, and the control of the lattice constant in GaP1-x-yAsyNx quaternary alloys is demonstrated. From the dependence of photoluminescence (PL) intensities on lattice mismatch to GaP substrates, we found that lattice-matching to substrates is necessary to obtain GaP1-x-yAsyNx alloys with high quality and intense PL. © 1998 Elsevier Science B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/S0022-0248(98)00336-4
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0032089854&origin=inward
  DOI ID：10.1016/S0022-0248(98)00336-4, ISSN：0022-0248, ORCID：48141583, SCOPUS ID：0032089854, Web of Science ID：WOS:000074730400099
• Investigation of luminescence properties of GaN single crystals grown on 3C-SiC substrates　　　　　　　　　　　　　　　
  J. Wu; H. Yaguchi; H. Nagasawa; Y. Yamaguchi; K. Onabe; Y. Shiraki; R. Ito
  Journal of Crystal Growth, Volume：189-190, First page：420, Last page：424, Jun. 1998, [Reviewed]
  Cathodoluminescence (CL) and photoluminescence (PL) investigations of single crystal GaN grown on 3C-SiC(1 0 0) substrates by metalorganic vapor-phase epitaxy are reported. The GaN grown on 3C-SiC substrates shows distinct crystal facets. We identified the square facet and inclined facet as cubic GaN and hexagonal GaN, respectively. We studied the luminescence properties from the square facet or from the inclined facets separately by CL. For the cubic GaN, a sharp excitonic transition and a weak DA pair transition were observed from the square facet. On the other hand, an emission line at 3.293 eV was obtained from the inclined facets. By studying its temperature dependence, we suggest that the 3.293 eV emission is due to the free electron to acceptor transition of hexagonal GaN. © 1998 Elsevier Science B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/S0022-0248(98)00312-1
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0032092034&origin=inward
  DOI ID：10.1016/S0022-0248(98)00312-1, ISSN：0022-0248, eISSN：1873-5002, ORCID：30384857, SCOPUS ID：0032092034, Web of Science ID：WOS:000074730400085
• Optical transitions in cubic GaN grown on GaAs(1 0 0) substrates by metalorganic vapor-phase epitaxy　　　　　　　　　　　　　　　
  Jun Wu; Hiroyuki Yaguchi; Kentaro Onabe; Ryoichi Ito; Yasuhiro Shiraki
  Journal of Crystal Growth, Volume：189-190, First page：415, Last page：419, Jun. 1998, [Reviewed]
  We investigated the optical transitions in cubic GaN films grown on GaAs(1 0 0) substrates by metalorganic vapor-phase epitaxy. The cubic GaN films show good optical quality. From temperature and excitation intensity dependence, the emission lines at 3.274 and 3.178 eV were assigned to the excitonic transition and the donor-acceptor pair transition, respectively. We also suggested an additional acceptor level (EA′ ≈ 212 meV) to explain the origin of the emission lines at 3.088 and 3.056 eV, on the basis of the excitation intensity dependence. © 1998 Elsevier Science B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/S0022-0248(98)00311-X
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0032093256&origin=inward
  DOI ID：10.1016/S0022-0248(98)00311-X, ISSN：0022-0248, eISSN：1873-5002, ORCID：56291665, SCOPUS ID：0032093256, Web of Science ID：WOS:000074730400084
• Fabrication of Pb(Zr,Ti)O3/MgO/GaN/GaAs structure for optoelectronic device applications　　　　　　　　　　　　　　　
  Atsushi Masuda; Shinya Morita; Hideki Shigeno; Akiharu Morimoto; Tatsuo Shimizu; Jun Wu; Hiroyuki Yaguchi; Kentaro Onabe
  Journal of Crystal Growth, Volume：189-190, First page：227, Last page：230, Jun. 1998, [Reviewed]
  Pb(Zr,Ti)O3 (PZT) films were deposited on cubic GaN/(1 0 0)GaAs for the first time with or without MgO buffer layer by pulsed laser ablation. MgO films were grown on cubic GaN with cube-on-cube epitaxy. It was found that MgO buffer layer is very useful for suppressing the diffusion of O and metal elements into GaN layer. Preferentially [1 0 0]-oriented perovskite PZT films were obtained on cubic GaN with MgO buffer layer although randomly oriented perovskite PZT films were obtained without MgO buffer layer. PZT/MgO/GaN structure is one of the promising candidates for integrated devices composed of ferroelectric waveguides and blue laser diodes. © 1998 Elsevier Science B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/S0022-0248(98)00241-3
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0032092953&origin=inward
  DOI ID：10.1016/S0022-0248(98)00241-3, ISSN：0022-0248, eISSN：1873-5002, ORCID：56291701, SCOPUS ID：0032092953, Web of Science ID：WOS:000074730400048
• Characterization of SiGe strained heterostructures grown by molecular beam epitaxy using a Si effusion cell　　　　　　　　　　　　　　　
  H. Yaguchi; T. Yamamoto; Y. Shiraki
  Thin Solid Films, Volume：321, Number：1-2, First page：241, Last page：244, May 1998, [Reviewed]
  We characterize SiGe strained heterostructures grown by molecular beam epitaxy (MBE) using a Si effusion cell which can be used at high temperatures up to 1700°C instead of an electron beam gun conventionally used in solid-source Si MBE. Photoluminescence is clearly observed from a Si/SiGe quantum well grown on a Si(001) substrate using the Si effusion cell. This indicates that the sample grown with the Si effusion cell is of good quality. It is found from X-ray diffraction measurement of a Ge/Si strained-layer superlattice grown on a Ge(001) substrate that good controllability of the growth rate can be realized by using the Si effusion cell. Optical transitions observed in the photoreflectance spectrum of the Ge/Si strained layer superlattice agree with the Kronig-Penny model calculation taking account of the non-parabolicity of the conduction band. © 1998 Elsevier Science S.A. All rights reserved.
  ELSEVIER SCIENCE SA, English, Scientific journal
  DOI：https://doi.org/10.1016/S0040-6090(98)00480-5
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0347537655&origin=inward
  DOI ID：10.1016/S0040-6090(98)00480-5, ISSN：0040-6090, CiNii Articles ID：80010404794, ORCID：48141850, SCOPUS ID：0347537655, Web of Science ID：WOS:000074745700044
• Polarization characteristics of crescent-shaped tensile-strained GaAsP/AlGaAs quantum wire-like lasers　　　　　　　　　　　　　　　
  Mitsuteru Ishikawa; Wugen Pan; Yasuhisa Kaneko; Hiroyuki Yaguchi; Kentaro Onabe; Ryoichi Ito; Yasuhiro Shiraki
  Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, Volume：37, Number：3 SUPPL. B, First page：1556, Last page：1558, Mar. 1998, [Reviewed]
  Crescent-shaped tensile-strained GaAsP/AlGaAs quantum wire-like lasers are fabricated on V-grooved GaAs(100) substrates by mctalorganic vapor phase epitaxy. Light-output versus current characteristics, polarized lasing spectra and near-field patterns show lasing from the quantum wires in the TM mode. The threshold current density per wire is as low as 500 A/cm2 and the lasing wavelength is 780 nm.
  JAPAN J APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.37.1556
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0344002874&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0344002874&origin=inward
  DOI ID：10.1143/JJAP.37.1556, ISSN：0021-4922, ORCID：30384867, SCOPUS ID：0344002874, Web of Science ID：WOS:000073664900113
• Metalorganic vapor phase epitaxy growth of high quality cubic GaN on GaAs (100) substrates　　　　　　　　　　　　　　　
  Jun Wu; Hiroyuki Yaguchi; Kentaro Onabe; Yasuhiro Shiraki; Ryoichi Ito
  Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, Volume：37, Number：3 SUPPL. B, First page：1440, Last page：1442, Mar. 1998, [Reviewed]
  We report on the growth of high quality cubic GaN films on GaAs (100) substrates by low pressure metalorganic vapor phase epitaxy. The GaN films exhibit a smooth surface which is free from cracks. X-ray diffraction shows the cubic nature of the GaN films. X-ray rocking curve with ω scan shows that the crystal quality of GaN films improves markedly with increasing growth temperatures. Photoluminescence measurements confirm the high quality of the cubic GaN films. The full width at half maximum of excitonic emission from the cubic GaN films is as narrow as 70meV at 300K.
  JAPAN SOC APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.37.1440
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0009207272&origin=inward
  DOI ID：10.1143/JJAP.37.1440, ISSN：0021-4922, ORCID：30384859, SCOPUS ID：0009207272, Web of Science ID：WOS:000073664900089
• GaAs/AlGaAs quantum structures grown in tetrahedral-shaped recesses on GaAs (111)B substrates by metalorganic vapor phase epitaxy　　　　　　　　　　　　　　　
  Tomoko Tsujikawa; Keishi Momma; Hiroyuki Yaguchi; Kentaro Onabe; Yasuhiro Shiraki; Ryoichi Ito
  Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, Volume：37, Number：3 SUPPL. B, First page：1493, Last page：1496, Mar. 1998, [Reviewed]
  GaAs/AlGaAs quantum structures were grown in tetrahedral-shaped recesses (TSRs) on GaAs (111)B substrates at different growth rates by metalorganic vapor phase epitaxy. Observation of cathodoluminescence revealed that GaAs quantum structures with different layer thicknesses were formed at {100} edge regions, {110} and {111} A sidewalls and the {111} bottom region of the TSR. The luminescence from the bottom region of the TSRs was clearly seen in the sample grown at a large growth rate. With increasing growth rate, the thickness in the bottom region increased, whereas the thickness at the edge regions decreased. This is explained by a reduction in the migration distance of Ga adatoms from the {111} bottom region to the other regions.
  JAPAN J APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.37.1493
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0043230458&origin=inward
  DOI ID：10.1143/JJAP.37.1493, ISSN：0021-4922, ORCID：30384856, SCOPUS ID：0043230458, Web of Science ID：WOS:000073664900101
• Self-assembled, very long II-VI semiconductor quantum wires　　　　　　　　　　　　　　　
  B. P. Zhang; W. X. Wang; T. Yasuda; Y. Segawa; H. Yaguchi; K. Onabe; K. Edamatsu; T. Itoh
  Materials Science and Engineering B, Volume：51, Number：1-3, First page：224, Last page：228, Feb. 1998, [Reviewed]
  Self-organized ZnCdSe quantum wires (QWRs) are realized on cleavage-induced GaAs (110) surfaces based on simultaneous selective growth and composition modulation. Formed on step tops, the QWRs are parallel to the [1̄10] direction and extend to millimeter order in length. Surface observations and optical studies demonstrate the formation of QWRs. A large piezo-electric field is observed in the QWRs, implying potential applications in nonlinear optoelectronic devices. © 1998 Elsevier Science S.A. All rights reserved.
  ELSEVIER SCIENCE SA, English, Scientific journal
  DOI：https://doi.org/10.1016/S0921-5107(97)00265-1
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0342391357&origin=inward
  DOI ID：10.1016/S0921-5107(97)00265-1, ISSN：0921-5107, ORCID：30384869, SCOPUS ID：0342391357, Web of Science ID：WOS:000072728800048
• Molecular beam epitaxy of SiGe heterostructures using a newly designed Si effusion cell　　　　　　　　　　　　　　　
  H. Yaguchi; T. Yamamoto; Y. Shiraki
  Materials Science and Engineering B, Volume：51, Number：1-3, First page：170, Last page：172, Feb. 1998, [Reviewed]
  We demonstrate the usefulness of a newly designed Si effusion cell which can be used at high temperatures up to 1700°C instead of a conventional electron beam evaporator in solid-source Si molecular beam epitaxy. The growth rate ranges from 0.005 to 0.5 Å s-1 at temperatures from 1350 to 1650°C and agrees well with the temperature dependence of the Si vapor pressure. Photoluminescence was observed from a Si/SiGe quantum well grown on a Si substrate using the Si effusion cell. This indicates that the sample has little defects or dislocations which may result in nonradiative recombination centers or deep levels. It is found from photoreflectance and X-ray diffraction measurements that excellent controllability of the growth rate can be realized by using the Si effusion cell. © 1998 Elsevier Science S.A. All rights reserved.
  ELSEVIER SCIENCE SA, English, Scientific journal
  DOI：https://doi.org/10.1016/S0921-5107(97)00254-7
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0347486931&origin=inward
  DOI ID：10.1016/S0921-5107(97)00254-7, ISSN：0921-5107, ORCID：48141848, SCOPUS ID：0347486931, Web of Science ID：WOS:000072728800037
• A new approach to ZnCdSe quantum dots　　　　　　　　　　　　　　　
  B. P. Zhang; T. Yasuda; W. X. Wang; Y. Segawa; K. Edamatsu; T. Itoh; H. Yaguchi; K. Onabe
  Materials Science and Engineering B, Volume：51, Number：1-3, First page：127, Last page：131, Feb. 1998, [Reviewed]
  We propose a new approach of fabricating ZnCdSe quantum dots (QDs) on ZnSe and GaAs (110) surfaces by simply depositing a ZnSe/ZnCdSe/ZnSe heterostructure. The growth conditions are selected to introduce surface roughness on the over grown ZnSe which allows the formation of ZnCdSe QDs. Optical studies unambiguously demonstrate the formation of QDs. Resolution-limited sharp emission lines are observed by micro-photoluminescences and the linewidths are much less than the thermal energy. As time goes on, intermittent behaviors of the QD emissions are observed. A proper selection of growth conditions is essential in obtaining ZnCdSe QDs by this method, especially on GaAs (110) surfaces. © 1998 Elsevier Science S.A. All rights reserved.
  ELSEVIER SCIENCE SA, English, Scientific journal
  DOI：https://doi.org/10.1016/S0921-5107(97)00245-6
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0031997271&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0031997271&origin=inward
  DOI ID：10.1016/S0921-5107(97)00245-6, ISSN：0921-5107, ORCID：56291699, SCOPUS ID：0031997271, Web of Science ID：WOS:000072728800028
• Exciton diffusion dynamics in quantum nanostructures on V-groove patterned substrates　　　　　　　　　　　　　　　
  N. Usami; Y. Shiraki; W. Pan; H. Yaguchi; K. Onabe
  Superlattices and Microstructures, Volume：23, Number：2, First page：395, Last page：400, 1998, [Reviewed]
  Time-resolved photoluminescence (PL) measurements were performed for two different quantum nanostructures on V-groove patterned substrates; SiGe/Si quantum wells (QWs) on V-grooved Si substrates and AlGaAs spontaneous vertical quantum wells on V-grooved GaAs substrates. Anomalous behaviours of the PL, such as the decrease of the decay time of the SiGe (111) QWs and the (111)A AlGaAs layer, were fully explained by taking the exciton diffusion towards the bottom of the V-groove into account, showing that the exciton diffusion driven by the spatial nonuniformity of the alloy compositions and/or geometry of the substrates is a key to controlling the PL properties of the nanostructures. © 1998 Academic Press Limited.
  ACADEMIC PRESS LTD, English, Scientific journal
  DOI：https://doi.org/10.1006/spmi.1996.0285
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=11544283825&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=11544283825&origin=inward
  DOI ID：10.1006/spmi.1996.0285, ISSN：0749-6036, CiNii Articles ID：80010189221, ORCID：56291662, SCOPUS ID：11544283825, Web of Science ID：WOS:000072396800032
• Cleaved cavity stimulated emission from an optically pumped cubic GaN/AlGaN heterostructure grown on GaAs (100) substrate　　　　　　　　　　　　　　　
  J. Wu; H. Yaguchi; K. Onabe; Y. Shiraki
  Applied Physics Letters, Volume：73, Number：14, First page：1931, Last page：1933, 1998, [Reviewed]
  Cubic GaN/AlGaN double heterostructure was grown on semi-insulating GaAs (100) substrate by metalorganic vapor phase epitaxy. Strong stimulated emission was observed from the cleaved edge of the optically pumped cubic GaN/AlGaN heterostructure at 15 K. The cavity was formed simply by cleaving the substrate. The stimulated emission was demonstrated by the superlinear increase of the output intensity and the highly transverse electric polarized nature. The stimulated emission showed an obvious redshift compared with the spontaneous one. © 1998 American Institute of Physics.
  AMER INST PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1063/1.122326
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0032487237&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0032487237&origin=inward
  DOI ID：10.1063/1.122326, ISSN：0003-6951, CiNii Articles ID：80010580213, ORCID：56291775, SCOPUS ID：0032487237, Web of Science ID：WOS:000076183300003
• カソ-ドルミネツセンスによる半導体低次元構造の評価 (日本電子顕微鏡学会第43回シンポジウム論文集--21世紀へ向けての新技術の展開--平成10年10月28日(水)〜30日(金),千葉大学けやき会館〔含 著者名索引〕) -- (ワ-クショップ カソ-ドルミネッセンスを使った機能評価法の発展)　　　　　　　　　　　　　　　
  矢口 裕之; 辻川 智子; 尾鍋 研太郎
  Volume：33, Number：2, First page：217, Last page：220, 1998
  Japanese
  ISSN：0417-0326, CiNii Articles ID：40002545376, CiNii Books ID：AN00145000
• Metalorganic vapor phase epitaxy growth and photoluminescence properties of cubic AlxGa1-xN　　　　　　　　　　　　　　　
  J. Wu; H. Yaguchi; K. Onabe; Y. Shiraki
  Applied Physics Letters, Volume：73, Number：2, First page：193, Last page：195, 1998, [Reviewed]
  We have grown cubic AlxGa1-xN (0AMER INST PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1063/1.121752
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0000148788&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0000148788&origin=inward
  DOI ID：10.1063/1.121752, ISSN：0003-6951, ORCID：30384858, SCOPUS ID：0000148788, Web of Science ID：WOS:000075275400021
• The optical process in AlInP/GaInP/AlInP quantum wells (vol 80, pg 4592, 1996)　　　　　　　　　　　　　　　
  Y Ishitani; S Minagawa; T Kita; T Nishino; H Yaguchi; Y Shiraki
  JOURNAL OF APPLIED PHYSICS, Volume：82, Number：11, First page：5876, Last page：5876, Dec. 1997, [Reviewed]
  AMER INST PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1063/1.366457
  DOI ID：10.1063/1.366457, ISSN：0021-8979, ORCID：30384885, Web of Science ID：WOS:A1997YH59000089
• Growth mechanism in the metalorganic vapor phase epitaxy of metastable GaP1-xNx alloys: A growth interruption study　　　　　　　　　　　　　　　
  Seiro Miyoshi; Hiroyuki Yaguchi; Kentaro Onabe; Yasuhiro Shiraki; Ryoichi Ito
  Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, Volume：36, Number：12 A, First page：7110, Last page：7118, Dec. 1997, [Reviewed]
  The metalorganic vapor phase epitaxy (MOVPE) of metastable GaP1-xNx alloys applying a growth interruption technique is performed. In the growth procedure, different from conventional MOVPE, a cycle of 1 ML growth and growth interruption (Ga precursor supply is turned off) is repeated. The nitrogen content (x) decreases with the increasing growth interruption time due to the desorption of nitrogen during the interruption. This means that the solid composition of the alloy is determined by the competition between the supply and the desorption of nitrogen at the film surface. The nitrogen adsorption/desorption model is presented. The time constant of the nitrogen desorption is obtained to be 0.47s at 670°C. It is clarified that in the conventional (without growth interruption) MOVPE of the alloys, low growth temperature and high growth rate decrease the nitrogen desorption from the film surface and thus result in a large nitrogen content. We succeeded in growing the alloys with x as large as 6.3% by using a low growth temperature (650°C) and a high growth rate (5 MLs/s).
  Scientific journal
  DOI：https://doi.org/10.1143/JJAP.36.7110
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0031376350&origin=inward
  DOI ID：10.1143/JJAP.36.7110, ISSN：0021-4922, ORCID：30384876, SCOPUS ID：0031376350, Web of Science ID：WOS:000071543500005
• Self formation and optical properties of II-VI semiconductor wire structures　　　　　　　　　　　　　　　
  Baoping Zhang; Wenxin Wang; Takashi Yasuda; Yanqiu Li; Yusaburo Segawa; Hiroyuki Yaguchi; Kentaro Onabe; Keiichi Edamatsu; Tadashi Itoh
  Japanese Journal of Applied Physics, Part 2: Letters, Volume：36, Number：11 SUPPL. B, First page：L1490, Last page：L1493, Nov. 1997, [Reviewed]
  Based on simultaneous selective growth and composition modulation, Zn1-xCdxSe wire structures are spontaneously formed on cleavage-induced GaAs (110) surfaces by deposition of a Zn1-yCdySe (x > y) alloy layer. The wire structures are formed on the top edge of the steps introduced by cleavage. These wires show a strongly polarized emission and a large piezoelectric effect, implying a potential for applications in nonlinear optoelectronic devices. This paper discusses a novel approach to semiconductor nanostructures.
  JAPAN SOC APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.36.L1490
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0031276855&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0031276855&origin=inward
  DOI ID：10.1143/JJAP.36.L1490, ISSN：0021-4922, ORCID：30384883, SCOPUS ID：0031276855, Web of Science ID：WOS:A1997YJ04500005
• The Gamma(c)-Gamma(v) transition energies of AlxIn1-xP alloys　　　　　　　　　　　　　　　
  Y Ishitani; H Hamada; S Minagawa; H Yaguchi; Y Shiraki
  JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, Volume：36, Number：11, First page：6607, Last page：6613, Nov. 1997, [Reviewed]
  The transition energies at 20 K for the Gamma(6c)-Gamma(7v) (electron-heavy hole). (E-s(hh)(x)) and for the Gamma(6c)-Gamma(6v(I)) (electron-light hole) (E-s(lb)(x)) of strained and disordered AlxIn1-xP (0.43 less than or equal to x less than or equal to 0.62) on GaAs substrates were measured using a photoreflectance method. They are expressed as E-s(hh)((x)) = 1.488(+/-0.020) + 2.30(+/-0.04).x, and E-s(lh)(x) = 1.738(+/-0.030) + 1.81(+/-0.06).x(eV). The Gamma(6c)-Gamma(8v) transition energies for unstrained layers (E,(ar)) were also measured at 20 K as Eu (x) = 1.418(+/- 0.007) + 2.42 (+/- 0.01).x(eV). The unstrained samples were InP, Al0.53In0.47P on a GaAs substrate and Al0.73In0.27P On it GaAs0.61P0.39 substrate. The shift of the transition energies due to stress was obtained from these transition energies. The hydrostatic and shear deformation potentials for AlxIn1-xP alloys were calculated to be -5.23(+/-0.60)eV and -1.67(+/-0.26) eV by comparing the experimental results and the theoretical formulae.
  JAPAN J APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.36.6607
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0031277384&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0031277384&origin=inward
  DOI ID：10.1143/JJAP.36.6607, ISSN：0021-4922, ORCID：30384884, SCOPUS ID：0031277384, Web of Science ID：WOS:000071172300005
• Electronic structure of (111)-GaAsP/AlGaAs strained-layer quantum wells　　　　　　　　　　　　　　　
  Xiong Zhang; Mitsuteru Ishikawa; Hiroyuki Yaguchi; Kentaro Onabe
  Surface Science, Volume：387, Number：1-3, First page：371, Last page：382, Oct. 1997, [Reviewed]
  The GaAs1-xPx/AlyGa1-yAs (x = 0.07-0.14, y = 0.3) strained-layer multiple quantum wells grown by metal-organic vapor phase epitaxy on GaAs-(111)B substrates have been characterized by X-ray diffraction and photoreflectance (PR) spectroscopy. By fitting the experimental results with the calculation which was based on the deformation potential theory modified by the strain-induced piezoelectric field, the energy band offset ratio for the conduction band at the heterointerface of GaAs1-xPx/AlyGa1-yAs was quantitatively determined to be Qc = 0.61 ± 0.03. This value was found to be nearly independent of the phosphorous composition x in the whole region that has been investigated in this study. Moreover, several anomalous phenomena observed with the PR measurement as well as the possible physical origins have also been discussed. © 1997 Elsevier Science B.V.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/S0039-6028(97)00401-9
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0031560008&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0031560008&origin=inward
  DOI ID：10.1016/S0039-6028(97)00401-9, ISSN：0039-6028, CiNii Articles ID：80009902754, ORCID：48141594, SCOPUS ID：0031560008, Web of Science ID：WOS:A1997YC84800043
• Photoluminescence properties of cubic GaN grown on GaAs(100) substrates by metalorganic vapor phase epitaxy　　　　　　　　　　　　　　　
  J Wu; H Yaguchi; K Onabe; R Ito; Y Shiraki
  APPLIED PHYSICS LETTERS, Volume：71, Number：15, First page：2067, Last page：2069, Oct. 1997, [Reviewed]
  Photoluminescence (PL) measurements were performed on cubic GaN films grown on GaAs(100) substrates by metalorganic vapor phase epitaxy. The cubic GaN films show a high optical quality that enables us to study the PL spectra in detail. From temperature and excitation intensity dependence, the emission lines at 3.274 and at 3.178 eV were assigned to the excitonic transition and the donor-acceptor pair transition, respectively. We also observed two additional emission lines at 3.088 and 3.056 eV. An excitonic emission at 3.216 eV with full width half maximum value as small as 73 meV was observed at 300 K. (C) 1997 American Institute of Physics.
  AMER INST PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1063/1.119344
  DOI ID：10.1063/1.119344, ISSN：0003-6951, ORCID：30384882, Web of Science ID：WOS:A1997YA20900003
• Crystal structure of GaN grown on 3C-SiC substrates by metalorganic vapor phase epitaxy　　　　　　　　　　　　　　　
  Jun Wu; Hiroyuki Yaguchi; Hiroyuki Nagasawa; Yoichi Yamaguchi; Kentaro Onabe; Yasuhiro Shiraki; Ryoichi Ito
  Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, Volume：36, Number：7 A, First page：4241, Last page：4245, Jul. 1997, [Reviewed]
  GaN films were grown on 3C-SiC substrates by metalorganic vapor phase epitaxy (MOVPE) using 1,1-dimethylhydrazine (DMHy) as the N source. The crystal structure was strongly affected by both the growth temperature and the V/III ratio. At 600°C, only hexagonal GaN films with their c-axis perpendicular to the substrate surface were grown. At 80°C, relatively high V/III ratios resulted in the growth of hexagonal GaN with their c-axis oriented in the [111] direction while cubic GaN films were obtained at lower V/III ratios. The origin of [111]-oriented hexagonal GaN is also discussed.
  JAPAN SOC APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.36.4241
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0031189839&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0031189839&origin=inward
  DOI ID：10.1143/JJAP.36.4241, ISSN：0021-4922, ORCID：30384874, SCOPUS ID：0031189839, Web of Science ID：WOS:A1997XR22300004
• Metalorganic vapor phase eitaxy growth features of AlGaAs in tetrahedral-shaped recesses on GaAs (111)B substrates　　　　　　　　　　　　　　　
  Tomoko Tsujikawa; Wugen Pan; Keishi Momma; Masahiro Kudo; Kunio Tanaka; Hiroyuki Yaguchi; Kentaro Onabe; Yasuhiro Shiraki; Ryoichi Ito
  Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, Volume：36, Number：6 SUPPL. B, First page：4102, Last page：4106, Jun. 1997, [Reviewed]
  We have investigated the compositional modulation of AlGaAs layers grown in tetrahedral-shaped recesses (TSRs) on n-type GaAs (111)B substrates using scanning electron microscopy, photoluminescence and cathodoluminescence. Growth hardly occurred between the TSRs, and complicated facets were seen in the TSR. Gallium-rich regions were formed around the edges between sidewalls rather than at the center of sidewalls and at the bottom region rather than the top region. To observe the facetting process during growth, GaAs/AlGaAs multilayers were also grown in TSRs. Aluminum compositional modulation is dependent not only on the difference in migration distances of Ga and Al atoms but also on the differences in the incorporating process among different facets.
  JAPAN SOC APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.36.4102
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0043230459&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0043230459&origin=inward
  DOI ID：10.1143/JJAP.36.4102, ISSN：0021-4922, ORCID：30384878, SCOPUS ID：0043230459, Web of Science ID：WOS:000073628300074
• Naturally formed ZnCdSe quantum dots on ZnSe (110) surfaces　　　　　　　　　　　　　　　
  BP Zhang; T Yasuda; Y Segawa; H Yaguchi; K Onabe; E Edamatsu; T Itoh
  APPLIED PHYSICS LETTERS, Volume：70, Number：18, First page：2413, Last page：2415, May 1997, [Reviewed]
  We successfully realized ZnCdSe quantum dots on a cleavage-induced ZnSe (110) surface by depositing a ZnSe/ZnCdSe/ZnSe heterostructure under growth conditions that cannot lead to layer-by-layer growth of ZnSe. This growth mode introduces surface roughness to the newly deposited ZnSe layer, and ZnCdSe quantum dots are then formed. Cathodoluminescence and microphotoluminescence measurements demonstrate the formation of quantum dots. (C) 1997 American Institute of Physics.
  AMER INST PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1063/1.118888
  DOI ID：10.1063/1.118888, ISSN：0003-6951, ORCID：30384879, Web of Science ID：WOS:A1997WZ07600027
• Nitrogen concentration dependence of photoluminescence decay time in GaP1-xNx alloys　　　　　　　　　　　　　　　
  Hiroyuki Yaguchi; Seiro Miyoshi; Hideo Arimoto; Shiro Saito; Hidefumi Akiyama; Kentaro Onabe; Yasuhiro Shiraki; Ryoichi Ito
  Solid-State Electronics, Volume：41, Number：2 SPEC. ISS., First page：231, Last page：233, Feb. 1997, [Reviewed]
  We report on the nitrogen concentration dependence of photoluminescence (PL) properties in GaP1-xNx alloys. Time-resolved PL measurements reveal that the radiative transition and relaxation processes in GaP1-zNx alloys with high nitrogen concentrations are significantly different from those with low concentrations where NNi lines are clearly observed. The PL decay profile shows two distinct exponential processes with fast and slow decay times for high concentrations. With increasing N concentration, the fast decay component becomes dominant and the slow decay time becomes longer. The fast decay is attributed to the relaxation to nonradiative recombination centers. The slow decay indicates the long radiative lifetime due to the weak localization of excitons and the slow relaxation due to the scattered spatial distribution of the states. This is consistent with the fact that the PL occurs at the tails of the density of states. © 1997 Elsevier Science Ltd.
  PERGAMON-ELSEVIER SCIENCE LTD, English, Scientific journal
  DOI：https://doi.org/10.1016/S0038-1101(96)00206-7
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0031076173&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0031076173&origin=inward
  DOI ID：10.1016/S0038-1101(96)00206-7, ISSN：0038-1101, CiNii Articles ID：80009442419, ORCID：56291672, SCOPUS ID：0031076173, Web of Science ID：WOS:A1997WF76300024
• Photoluminescence excitation spectroscopy of GaP1 - XNx alloys: Conduction-band-edge formation by nitrogen incorporation　　　　　　　　　　　　　　　
  Hiroyuki Yaguchi; Seiro Miyoshi; Goshi Biwa; Masaya Kibune; Kentaro Onabe; Yasuhiro Shiraki; Ryoichi Ito
  Journal of Crystal Growth, Volume：170, Number：1-4, First page：353, Last page：356, Jan. 1997, [Reviewed]
  We have investigated the conduction-band-edge formation in GaP1 - xNx alloys by nitrogen incorporation into GaP using photoluminescence excitation (PLE) spectroscopy. The PLE spectra of GaP1 - xNx alloys with various nitrogen concentrations show that the absorption edge shifts to lower energies with increasing nitrogen concentration. From the nitrogen concentration dependence of the absorption edge energy we found that the conduction-band-edge formation in GaP1 - xNx alloys originates from the formation of the A line.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/S0022-0248(96)00592-1
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0030680373&origin=inward
  DOI ID：10.1016/S0022-0248(96)00592-1, ISSN：0022-0248, CiNii Articles ID：80009462734, ORCID：56291666, SCOPUS ID：0030680373, Web of Science ID：WOS:A1997WD06200066
• In-plane polarization properties of GaAsP/AlAs strained quantum wells on GaAs(113)A and (114)A substrates
  N. Hiroyasu; H. Yaguchi; K. Onabe; Y. Shiraki; R. Ito
  Institute of Physics Conference Series, Volume：155, First page：771, Last page：774, 1997
  Scientific journal
  ORCID：56291697, Web of Science ID：WOS:A1997BJ12N00181
• A highly luminescent crescent-shaped tensile-strained GaAsP/AlGaAs quantum wire laser structure　　　　　　　　　　　　　　　
  Wugen Pan; Hiroyuki Yaguchi; Yoshihiko Hanamaki; Mitsuteru Ishikawa; Yasuhisa Kaneko; Kentaro Onabe; Ryoichi Ito; Yasuhiro Shiraki
  Journal of Crystal Growth, Volume：170, Number：1-4, First page：585, Last page：589, Jan. 1997, [Reviewed]
  We report a highly luminescent crescent-shaped tensile-strained GaAsP/AlGaAs quantum wire (QWR) laser structure on 3 μm periodic V-grooves grown by low-pressure (100 Torr) metalorganic vapor phase epitaxy (MOVPE). Photoluminescence studies show that carriers are efficiently captured from neighboring quantum well layers (QWLs) into QWRs, which give efficient luminescence. The QWR light emitting diode (LED) shows polarization insensitivity resulting from the tensile strain properties of the QWR structure.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/S0022-0248(96)00593-3
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0030687245&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0030687245&origin=inward
  DOI ID：10.1016/S0022-0248(96)00593-3, ISSN：0022-0248, CiNii Articles ID：80009462781, ORCID：56291746, SCOPUS ID：0030687245, Web of Science ID：WOS:A1997WD06200113
• Self Formation and Photoluminescence of II-VI Quantum Wires on GaAs(110) Surfaces　　　　　　　　　　　　　　　
  B. P. Zhang; W. X. Wang; G. Isoya; T. Yasuda; Y. Segawa; H. Yaguchi; K. Onabe; K. Edamatsu; T. Itoh
  Nonlinear Optics, Volume：18, Number：2-4, First page：133, Last page：136, 1997
  Scientific journal
  ORCID：48141781, SCOPUS ID：0031347795
• MOVPE Growth of GaPAsN Quaternary Alloys Lattice-Matched to GaP　　　　　　　　　　　　　　　
  Goshi Biwa; Hiroyuki Yaguchi; Kentaro Onabe; Yasuhiro Shiraki
  MRS Proceedings, Volume：482, Jan. 1997
  Cambridge University Press ({CUP}), Scientific journal
  DOI：https://doi.org/10.1557/proc-482-173
  DOI ID：10.1557/proc-482-173, ISSN：1946-4274, ORCID：48141416, SCOPUS ID：0031389252, Web of Science ID：WOS:000073983100026
• The optical processes in AlInP/GaInP/AlInP quantum wells　　　　　　　　　　　　　　　
  Y Ishitani; S Minagawa; T Kita; T Nishino; H Yaguchi; Y Shiraki
  JOURNAL OF APPLIED PHYSICS, Volume：80, Number：8, First page：4592, Last page：4598, Oct. 1996, [Reviewed]
  The optical processes in AlInP/GaInP/AlInP quantum wells free from long-range ordering are examined by photoluminescence (PL), photoluminescence excitation (PLE), acid photoreflectance (PR) measurements. The PL method observes lower transition energy than the PLE and the PR methods which observe the space-averaged transition energy. This is because PL originates from localized lower-energy states to which an exciton state relaxes. By analyzing these measurements carried on 20- and 60-Angstrom-wide wells, the reason for this deviation is ascribed to the fluctuation of the transition energy due to the local variation of the well width by one molecular layer. The plausible share of the band offset for the conduction band against the energy gap difference at the Gamma point is obtained by comparing the experimentally obtained relative position of the energy levels in AlInP barriers and the 20 Angstrom GaInP well with the calculated ones. This is found to be 0.75 (+/-0.06). (C) 1996 American Institute of Physics.
  AMER INST PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1063/1.363829
  DOI ID：10.1063/1.363829, ISSN：0021-8979, ORCID：30384893, Web of Science ID：WOS:A1996VM27200055
• Anomalous optical absorption in ZnCdSe/ZnSe single quantum wells　　　　　　　　　　　　　　　
  Baoping Zhang; Takanari Yasui; Takashi Yasuda; Yusaburo Segawa; Hiroyuki Yaguchi; Yasuhiro Shiraki
  Solid State Communications, Volume：99, Number：12, First page：897, Last page：900, Sep. 1996, [Reviewed]
  The optical absorption in ZnCdSe/ZnSe single quantum wells was studied by analyzing their reflectance spectra measured by a Fourier transform spectrometer. At lower temperatures, we observed a decrease in the excitonic absorption. This is qualitatively explained using a polariton model with the absorption dominated by phonon scattering. We present a comparison with III-V materials. The result confirms the polariton model of light propagation in quantum wells. Copyright © 1996 Published by Elsevier Science Ltd.
  PERGAMON-ELSEVIER SCIENCE LTD, English, Scientific journal
  DOI：https://doi.org/10.1016/0038-1098(96)00320-1
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0030244101&origin=inward
  DOI ID：10.1016/0038-1098(96)00320-1, ISSN：0038-1098, CiNii Articles ID：80009163673, ORCID：56291690, SCOPUS ID：0030244101, Web of Science ID：WOS:A1996VF72800007
• Rectangular AlGaAs/AlAs quantum wires using spontaneous vertical quantum wells　　　　　　　　　　　　　　　
  Wugen Pan; Hiroyuki Yaguchi; Kentaro Onabe; Ryoichi Ito; Noritaka Usami; Yasuhiro Shiraki
  Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, Volume：35, Number：2 SUPPL. B, First page：1214, Last page：1216, Feb. 1996, [Reviewed]
  We propose a lateral confinement enhanced rectangular AlGaAs/AlAs quantum wire (QWR) structure grown in situ, which utilizes the Ga-rich AlGaAs spontaneous vertical quantum wells formed during the growth of the AlGaAs epilayer in the V-grooves. AlGaAs/AlAs QWR structures have been grown on V/grooved substrates by low-pressure metalorganic vapor phase epitaxy (MOVPE), and been investigated by transmission electron microscopy, photoluminescence and cathodoluminescence measurements.
  JAPAN J APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.35.1214
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0030080393&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0030080393&origin=inward
  DOI ID：10.1143/JJAP.35.1214, ISSN：0021-4922, ORCID：30384891, SCOPUS ID：0030080393, Web of Science ID：WOS:A1996UD94100088
• Characterization of Si delta-doped GaAs using photoellipsometry and photoreflectance　　　　　　　　　　　　　　　
  M Mochizuki; K Kobayashi; H Yaguchi; T Saitoh; YM Xiong
  INTERNATIONAL SYMPOSIUM ON POLARIZATION ANALYSIS AND APPLICATIONS TO DEVICE TECHNOLOGY, Volume：2873, First page：270, Last page：273, 1996
  SPIE - INT SOC OPTICAL ENGINEERING, English, International conference proceedings
  DOI：https://doi.org/10.1117/12.246238
  DOI ID：10.1117/12.246238, ORCID：56291748, Web of Science ID：WOS:A1996BG27F00067
• Characterization of modulation-doped n-AlxGa1-xAs/GaAs heterostructure using spectroscopic ellipsometry and photoreflectance　　　　　　　　　　　　　　　
  CC Wong; M Mochizuki; H Yaguchi; T Saitoh; YM Xiong
  INTERNATIONAL SYMPOSIUM ON POLARIZATION ANALYSIS AND APPLICATIONS TO DEVICE TECHNOLOGY, Volume：2873, First page：226, Last page：229, 1996
  SPIE - INT SOC OPTICAL ENGINEERING, English, International conference proceedings
  DOI：https://doi.org/10.1117/12.246226
  DOI ID：10.1117/12.246226, Web of Science ID：WOS:A1996BG27F00056
• Growth temperature dependence of AlGaAs spontaneous vertical quantum wells on V-grooved substrates by low-pressure metalorganic vapor phase epitaxy　　　　　　　　　　　　　　　
  Wugen Pan; Hiroyuki Yaguchi; Kentaro Onabe; Yasuhiro Shiraki; Ryoichi Ito
  Journal of Crystal Growth, Volume：158, Number：3, First page：205, Last page：209, Jan. 1996, [Reviewed]
  We have studied the growth of AlGaAs on V-grooved GaAs substrates by low-pressure (100 Torr) metalorganic vapor phase epitaxy (MOVPE) in the temperature range of 600 to 700°C. The growth temperature dependence of facet formation, the facet dependence of AlGaAs composition on the V-grooves, and the growth temperature dependence of spontaneous vertical quantum well (SVQW) widths have been investigated by low temperature photoluminescence (PL), transmission electron micrograph (TEM) and spectrally and spatially resolved low temperature cathodoluminescence (CL). The width of the SVQW varies from 140 to 250 Å with increasing the growth temperature from 600 to 700°C.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/0022-0248(95)00449-1
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0030561998&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0030561998&origin=inward
  DOI ID：10.1016/0022-0248(95)00449-1, ISSN：0022-0248, CiNii Articles ID：80008768230, ORCID：48141804, SCOPUS ID：0030561998, Web of Science ID：WOS:A1996TR88900003
• Built-in Electric Field Strength in InP/n+-InP Determined by Photoellipsometry and Photoreflectance
  Yasuhiro SHIRAKI; Yi-Ming XIONG; HIROYUKI YAGUCHI
  Extended Abstracts of the International Conference on Solid State Devices and Materials, 1996
  Scientific journal
  DOI：https://doi.org/10.7567/SSDM.1996.PD-7-3
  DOI ID：10.7567/SSDM.1996.PD-7-3, ORCID：56291753
• Time-resolved photoluminescence study on AlxGa1-xAs spontaneous vertical quantum well structures　　　　　　　　　　　　　　　
  Noritaka Usami; Wugen Pan; Hiroyuki Yaguchi; Ryoichi Ito; Kentaro Onabe; Hidefumi Akiyama; Yasuhiro Shiraki
  Applied Physics Letters, Volume：68, Number：23, First page：3221, Last page：3223, 1996, [Reviewed]
  We report on time-resolved photoluminescence study of AlxGa1-xAs spontaneous vertical quantum well (SVQW) structures on GaAs V-grooved substrates. Four distinct photoluminescence peaks are observed originating from the spatial nonuniformity of the alloy compositions spontaneously formed during metalorganic vapor phase epitaxial growth. The decay time of the (111)A sidewall AlGaAs decreased with increasing temperature, while that of the SVQW increased. The rise time of the SVQW was found to be longer than the typical value of the exciton formation and increases with increasing temperature, indicating that the exciton formation is not limiting factor of the rise time. These results are explained in terms of the exciton diffusion toward the SVQW from the outer AlGaAs layers with less Ga compositions. In addition, two dimensionality of the SVQW was evidenced by temperature dependence of the radiative lifetime. © 1996 American Institute of Physics.
  AMER INST PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1063/1.116443
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0030567631&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0030567631&origin=inward
  DOI ID：10.1063/1.116443, ISSN：0003-6951, ORCID：30384895, SCOPUS ID：0030567631, Web of Science ID：WOS:A1996UN63500004
• TENSILE-STRAINED GAASP/ALGAAS QUANTUM-WELLS GROWN BY LOW-PRESSURE METALORGANIC VAPOR-PHASE EPITAXY　　　　　　　　　　　　　　　
  WG PAN; H YAGUCHI; K ONABE; R ITO; Y SHIRAKI
  JOURNAL OF APPLIED PHYSICS, Volume：78, Number：5, First page：3517, Last page：3519, Sep. 1995, [Reviewed]
  Tensile-strained GaAs0.89P0.11/Al0.33Ga0.67As quantum wells have been grown by low-pressure metalorganic vapor phase epitaxy. The grown samples have been studied by low-temperature (6 K) and 100 K in-plane photoluminescence as well as cross-sectional polarized photoluminescence measurements. The experimental results show the coincident or reversal point of the light- and heavy-hole related transitions at the well width of 60 Angstrom, above which the low-temperature photoluminescence is given by the transition 1e-1lh. A theoretical calculation agrees well with the experimental results. (C) 1995 American Institute of Physics.
  AMER INST PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1063/1.359987
  DOI ID：10.1063/1.359987, ISSN：0021-8979, ORCID：30384899, Web of Science ID：WOS:A1995RR84500099
• The in Situ Growth of Lateral Confinement Enhanced Rectangular AlGaAs/AlAs Quantum Wires by Utilizing the Spontaneous Vertical Quantum Wells　　　　　　　　　　　　　　　
  PAN Wugen; YAGUCHI Hiroyuki; ONABE Kentaro; ITO Ryoichi; USAMI Noritaka; SHIRAKI Yasuhiro
  Volume：1995, First page：737, Last page：739, Aug. 1995
  English
  CiNii Articles ID：10017203168, CiNii Books ID：AA10777858
• Optical property of GaAsP/AlGaAs strained-layer quantum well grown QA> on GaAs-(111)B substrate　　　　　　　　　　　　　　　
  Xiong Zhang; Koichi Karaki; Hiroyuki Yaguchi; Kentaro Onabe; Ryoichi Ito; Yasuhiro Shiraki
  Applied Physics Letters, Volume：66, Number：2, First page：186, Last page：188, 1995, [Reviewed]
  GaAs1-xPx/AlyGa1-yAs (x=0.07-0.15, y=0.3) strained-layer quantum wells have been grown on GaAs-(111)B substrates by low-pressure metalorganic vapor phase epitaxy and characterized by photoluminescence (PL) spectroscopy. Evident energy blue shifts of the excitonic transition peaks (some of them as large as 33 meV) were achieved by increasing the excitation power during the PL measurement. The large optical nonlinearity mainly due to the strain-induced piezoelectric field screened by the photoexcited carriers, is comparable to, or larger than, the reported values for a self-electro-optical effect device or other (111)-oriented strained-layer quantum well structures which are composed of InGaAs/GaAs or GaAs/GaAsP. This fact indicates that our (111)-GaAsP/AlGaAs strained-layer quantum well is a good candidate for making optoelectronic devices like optical switches and modulators. © 1995 American Institute of Physics.
  AMER INST PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1063/1.113129
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=36449000705&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=36449000705&origin=inward
  DOI ID：10.1063/1.113129, ISSN：0003-6951, ORCID：30384898, SCOPUS ID：36449000705, Web of Science ID：WOS:A1995QA69800025
• GROWTH-PARAMETERS FOR METASTABLE GAP1-XNX ALLOYS IN MOVPE
  S MIYOSHI; H YAGUCHI; K ONABE; Y SHIRAKI; R ITO
  COMPOUND SEMICONDUCTORS 1994, Volume：141, Number：141, First page：97, Last page：100, 1995, [Reviewed]
  In order to clarify what determines the solid composition (x) in the metalorganic vapor phase epitaxy (MOVPE) of metastable GaP1-xNx alloys, we applied a growth interruption technique in this alloy growth. In our growth procedure, different from conventional MOVPE, the cycle of similar to 1 ML growth and growth interruption (only Ga precursor supply is turned off) is repeated. As increasing the growth interruption time, x decreases. This indicates that nitrogen atoms desorb from the film surface and that phosphorus atoms occupy the vacant sites during the growth interruption. The time constant of this substitution process is obtained to be 0.71, 0.47 and 0.39 sec at 655, 670 and 685 degrees C, respectively. This result can explain the growth temperature dependence and the growth rate dependence of x in the conventional MOVPE of this alloy system. It also gives a guide to growing the alloys with large x.
  IOP PUBLISHING LTD, English, Scientific journal
  ISSN：0951-3248, ORCID：30384897, Web of Science ID：WOS:A1995BC92S00018
• Composition profile of an AlGaAs epilayer on a V-grooved substrate grown by low-pressure metalorganic vapor phase epitaxy　　　　　　　　　　　　　　　
  Wugen Pan; Hiroyuki Yaguchi; Kentaro Onabe; Ryoichi Ito; Yasuhiro Shiraki
  Applied Physics Letters, Volume：67, Number：7, First page：959, Last page：961, 1995, [Reviewed]
  A composition distribution of an AlxGa1-xAs epilayer on a V-grooved substrate grown by low-pressure metalorganic vapor phase epitaxy is described. The aluminum (Al) content of an AlxGa1-xAs epilayer on a V-grooved substrate is found to be on the order of x (111)A>xtop(100)>xedge-facet>x bottom-intersection by using spectrally and spatially resolved low temperature cathodoluminescence (CL) measurements. The composition difference between (111)A surfaces and bottom intersections is as much as 30%. The resulting spontaneous vertical quantum wells and spontaneous waveguides in the bottom intersections are expected to be applicable in low-threshold current laser devices.© 1995 American Institute of Physics.
  AMER INST PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1063/1.114708
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=21544436485&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=21544436485&origin=inward
  DOI ID：10.1063/1.114708, ISSN：0003-6951, ORCID：30384896, SCOPUS ID：21544436485, Web of Science ID：WOS:A1995RN57500028
• Effect of growth interruption on the interface flatness in metalorganic vapor phase epitaxy-grown GaAs/GaAsP heterostructures　　　　　　　　　　　　　　　
  Kazunobu Ota; Hiroyuki Yaguchi; Kentaro Onabe; Ryoichi Ito; Yasuhiro Shiraki
  Journal of Crystal Growth, Volume：145, Number：1-4, First page：819, Last page：823, Dec. 1994, [Reviewed]
  The interface flatness of metalorganic vapor phase epitaxy-grown GaAs/GaAsP strained barrier quantum wells has been studied with photoluminescence (PL). The PL peak clearly splits into two peaks when the growth rate is less than 1.7 Å/s or when the growth interruptions are introduced at the heterointerfaces. The energy separation between the two peaks corresponds to the well-width difference by a single monolayer. This indicates that the heterointerfaces are smoothed and that the islands of large lateral sizes are grown at the heterointerfaces. The growth interruption has been carried out either at the top (GaAsP on GaAs) or the bottom (GaAs on GaAsP) interface. It is found that the growth interruption is effective for smoothing both heterointerfaces. In addition, when the growth rate is 3.5 Å/s, the flatness of the growth front is retained during the growth of 90 Å layer. © 1994.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/0022-0248(94)91148-7
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0028762033&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0028762033&origin=inward
  DOI ID：10.1016/0022-0248(94)91148-7, ISSN：0022-0248, CiNii Articles ID：80008075962, ORCID：56291705, SCOPUS ID：0028762033, Web of Science ID：WOS:A1994QC54300129
• Metalorganic vapor phase epitaxial growth and luminescence properties of GaAs/GaAsP quantum wires　　　　　　　　　　　　　　　
  Wugen Pan; Hiroyuki Yaguchi; Kentaro Onabe; Kazumi Wada; Yasuhiro Shiraki; Ryoichi Ito
  Journal of Crystal Growth, Volume：145, Number：1-4, First page：702, Last page：706, Dec. 1994, [Reviewed]
  Metalorganic vapor phase epitaxy (MOVPE) of GaAs/GaAsP quantum wires (QWRs) has been attempted on V-grooved GaAs (100) substrates. Intense photoluminescence (PL) from the wires as well as from the flat (100) quantum well layers (QWLs) has been obtained. The excitation-power dependence of the Pl spectra confirms the efficient capture and confinement of free carriers in the wire regions. The top views of cathodoluminescence (CL) images show that the QWR structures have been successfully grown. The polarization of PL shows a strong optical anistropy in QWRs due to two-dimensional quantum confinement. This is the first successful fabrication of GaAs/GaAsP QWR structures. © 1994.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/0022-0248(94)91130-4
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0028761934&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0028761934&origin=inward
  DOI ID：10.1016/0022-0248(94)91130-4, ISSN：0022-0248, eISSN：1873-5002, CiNii Articles ID：80008075944, ORCID：56291683, SCOPUS ID：0028761934, Web of Science ID：WOS:A1994QC54300111
• Surface orientation dependence of growth rate of cubic GaN　　　　　　　　　　　　　　　
  Masaki Nagahara; Seiro Miyoshi; Hiroyuki Yaguchi; Kentaro Onabe; Yasuhiro Shiraki; Ryoichi Ito
  Journal of Crystal Growth, Volume：145, Number：1-4, First page：197, Last page：202, Dec. 1994, [Reviewed]
  The metalorganic vapor phase epitaxy (MOVPE) growth of cubic GaN has been performed on the patterned GaAs(100) substrates which have (111)A or (111)B facets. It is found that the growth features are strongly dependent on the configuration of the pattern. It is deduced that these features come from the surface-orientation-dependent growth rate, which is in the order (111)B > (100) > (111)A, combined with the diffusion of Ga adatoms on the surface. Taking advantage of the growth on the patterned substrates, the diffusion length of the Ga adatoms on the GaAs(100) surface is estimated to be several microns in the typical case. © 1994.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/0022-0248(94)91050-2
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0028761939&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0028761939&origin=inward
  DOI ID：10.1016/0022-0248(94)91050-2, ISSN：0022-0248, CiNii Articles ID：80008075864, ORCID：56291698, SCOPUS ID：0028761939, Web of Science ID：WOS:A1994QC54300031
• INTERMEDIATE RANGE BETWEEN N-DOPED GAP AND GAP1-XNX ALLOYS - DIFFERENCE IN OPTICAL-PROPERTIES　　　　　　　　　　　　　　　
  S MIYOSHI; H YAGUCHI; K ONABE; R ITO; Y SHIRAKI
  JOURNAL OF CRYSTAL GROWTH, Volume：145, Number：1-4, First page：87, Last page：92, Dec. 1994, [Reviewed]
  Metalorganic vapor phase epitaxy (MOVPE) grown GaP1-xNx metastable alloys with relatively dilute nitrogen concentrations (0.03% less than or equal to 1.4%, i.e., 1 x 10(19) less than or equal to [N] less than or equal to 3 x 10(20) cm(-3)) have been studied with photoluminescence (PL). These nitrogen concentrations are especially interesting because they mediate between the N-doped GaP ([N] similar to 10(19) cm(-3)), where the PL spectrum is represented by the emissions due to excitons bound to nitrogen atom pairs (NNi, i = 1, 2, 3,...), and the alloy, where the PL should be associated with the band gap. The nitrogen concentration dependence of the PL spectra shows that the dominant emission changes from the shallow NNi centers (NN4, NN5) to the deepest one (NN1) with increasing x. The temperature dependence of the PL shows a similar systematic change in the spectrum. the integrated PL intensity versus x relationship indicates that at x > 0.4% (approximate to 1 x 10(20) cm(-3)) nitrogen-doped GaP may be properly looked upon as a GaP1-xNx alloy.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/0022-0248(94)91033-2
  DOI ID：10.1016/0022-0248(94)91033-2, ISSN：0022-0248, CiNii Articles ID：80008075847, ORCID：56291750, Web of Science ID：WOS:A1994QC54300014
• TEMPERATURE-DEPENDENCE OF PHOTOLUMINESCENCE LINEWIDTH IN GAAS/GAASP STRAINED-LAYER QUANTUM-WELL STRUCTURES　　　　　　　　　　　　　　　
  XN ZHANG; Y SHIRAKI; H YAGUCHI; K ONABE; R ITO
  JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B, Volume：12, Number：4, First page：2293, Last page：2298, Jul. 1994, [Reviewed]
  The temperature dependence of photoluminescence (PL) spectra for the GaAs/GaAsP strained-layer single quantum well structures has been investigated in detail. For temperatures below 77 K, the PL linewidth was found to first decrease and then to increase slowly as the temperature was enhanced. This phenomenon was clearly seen for the GaAs/Ga.AsP strained-barrier quantum wells exhibiting higher dislocation densities than the GaAs/GaAsP strained-well quantum wells. This fact strongly suggests that beside the unintentionally introduced impurities, the misfit dislocations may also play an important role in determining the temperature-dependent PL linewidth.
  AMER INST PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1116/1.587755
  DOI ID：10.1116/1.587755, ISSN：1071-1023, ORCID：30384911, Web of Science ID：WOS:A1994PD16100003
• Formation of Cubic GaN on (111)B GaAs by Metal-Organic Vapor-Phase Epitaxy with Dimethylhydrazine　　　　　　　　　　　　　　　
  Noriyuki Kuwano; Kenki Kobayashi; Kensuke Oki; Seiro Miyoshi; Hiroyuki Yaguchi; Kentaro Onabe; Yasuhiro Shiraki
  Japanese Journal of Applied Physics, Volume：33, Number：6R, First page：3415, Last page：3416, Jun. 1994, [Reviewed]
  The microstructure of GaN grown on (111)B GaAs by a metal-orgnic vapor-phase epitaxy method has been examined by transmission electron microscopy. Trimethylgallium and dimethylhydrazine were used as the source materials. It was revealed that the GaN crystal has a zincblende structure and is formed heterogeneously penetrating into the GaAs substrate. In a GaN crystal, stacking faults propagate on (111) planes other than those normal to the growth direction. © 1994 The Japan Society of Applied Physics.
  Scientific journal
  DOI：https://doi.org/10.1143/JJAP.33.3415
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0028442419&origin=inward
  DOI ID：10.1143/JJAP.33.3415, ISSN：0021-4922, eISSN：1347-4065, ORCID：30384903, SCOPUS ID：0028442419, Web of Science ID：WOS:A1994PT64200021
• PHOTOREFLECTANCE STUDY OF INTERFACE ROUGHNESS IN GE/SIGE STRAINED-LAYER HETEROSTRUCTURES　　　　　　　　　　　　　　　
  H YAGUCHI; K TAI; K TAKEMASA; K ONABE; Y SHIRAKI; R ITO
  JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, Volume：33, Number：4B, First page：2353, Last page：2356, Apr. 1994, [Reviewed]
  Ge/SiGe strained-layer heterostructures have been investigated using photoreflectance (PR) spectroscopy. On the basis of the comparison between the experimental and calculated quantum well-related transition energies formed at the GAMMA point, band discontinuities at the Ge/SiGe heterojunction are determined and found to vary linearly with Ge content in the SiGe layer. Conduction band offset ratio Q(c) (= DELTAE(c)/(DELTAE(c) + DELTAE(v)HH)) at the GAMMA point is evaluated to be 0.68 +/- 0.08. From the intrinsic linewidth of the quantum well-related transitions, roughness at the Ge/SiGe heterointerface has been characterized for the first time and is estimated to be +/-1 monolayer (ML). In addition, the splittings in the PR spectra are observed in some samples at low temperatures. These splittings are due to the difference in the well width and correspond to the height (or depth) of about 10 ML.
  JAPAN J APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.33.2353
  DOI ID：10.1143/JJAP.33.2353, ISSN：0021-4922, ORCID：30384908, Web of Science ID：WOS:A1994NR95900044
• Valence-subband level crossing in GaAs/GaAsP strained-barrier quantum well structures observed by circularly polarized photoluminescence excitation spectroscopy　　　　　　　　　　　　　　　
  Hiroyuki Yaguchi; Kazunobu Ota; Yutaka Takahashi; Koji Muraki; Kentaro Onabe; Yasuhiro Shiraki; Ryoichi Ito
  Solid State Electronics, Volume：37, Number：4-6, First page：915, Last page：918, 1994, [Reviewed]
  We have investigated the level configuration of the valence subbands in GaAs/GaAs1-xPx (x = 0.23) strained-barrier quantum well structures as a function of the well width. Circularly polarized photoluminescence excitation (CPPLE) spectroscopy was used to identify the heavy- or light-hole character of the optical transitions. Distinct polarization properties were observed in the strain-split heavy- and light-hole bands in the GaAsP barriers, which indicates the photoexcited electrons in the barriers retain spin orientation well even after the capture into the well and the relaxation process. Utilizing this polarization tendency of the transitions in the barriers, we could distinguish unequivocally the heavy- and light-hole character of the quantum well-related transitions. By varying the well width systematically, we observed the level crossing between n = 1 heavy- and light-hole transitions around the well width of 4 nm. This is in good agreement with the calculation based on the effective mass approximation. © 1994.
  PERGAMON-ELSEVIER SCIENCE LTD, English, Scientific journal
  DOI：https://doi.org/10.1016/0038-1101(94)90325-5
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0028408432&origin=inward
  DOI ID：10.1016/0038-1101(94)90325-5, ISSN：0038-1101, CiNii Articles ID：80007544207, ORCID：56291777, SCOPUS ID：0028408432, Web of Science ID：WOS:A1994NE79600089
• Formation of facetted heterointerfaces of cubic GaN grown on GaAs(001) by metalorganic vapor phase epitaxy
  N KUWANO; K KOBAYASHI; Y TAKEICHI; K OKI; S MIYOSHI; H YAGUCHI; K ONABE; Y SHIRAKI
  ELECTRON MICROSCOPY 1994, VOLS 2A AND 2B, First page：619, Last page：620, 1994, [Reviewed]
  EDITIONS PHYSIQUE, English, International conference proceedings
  ORCID：56291582, Web of Science ID：WOS:A1994BE09Y00300
• TRANSMISSION ELECTRON-MICROSCOPE OBSERVATION OF CUBIC GAN GROWN BY METALORGANIC VAPOR-PHASE EPITAXY WITH DIMETHYLHYDRAZINE ON (001) GAAS　　　　　　　　　　　　　　　
  N KUWANO; Y NAGATOMO; K KOBAYASHI; K OKI; S MIYOSHI; H YAGUCHI; K ONABE; Y SHIRAKI
  JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, Volume：33, Number：1A, First page：18, Last page：22, Jan. 1994, [Reviewed]
  Cross-sectional transmission electron microscope observation has been performed on the microstructure of GaN films grown on a (001) GaAs substrate by metalorgahic vapor phase epitaxy (MOVPE) using l,l-dimethylhydrazine (DMHy) and trimethylgallium (TMG) as the sources of nitrogen and gallium, respectively. Before the deposition, the surface of the substrate was nitrided with DMHy. High-resolution images and electron diffraction patterns confirmed that the GaN films have a zincblende structure (beta-GaN) with the lattice constant of a(GaN)=0.454 nm, and contain bands of stacking faults parallel to (111) planes. The interface between GaN and GaAs is made of (111) facets with no interlayer. Misfit dislocations are found to be inserted on the interface approximately every five atomic planes of GaAs. The nitridation treatment with only DMHy for 130 min is found to form a thick layer of beta-GaN on the (001) GaAs substrate. Nuclei of beta-GaN formed by the pretreatment of surface nitridation play an important role in growing GaN in a zincblende structure during the supply of DMHy and TMG. The formation of facets on the top surface of GaN and on the interface of GaN/GaAs is explained in terms of the diffusion of arsenic in beta-GaN. The characteristics of the structure of GaN films grown at 600 and 650 degrees C are also presented.
  JAPAN J APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.33.18
  DOI ID：10.1143/JJAP.33.18, ISSN：0021-4922, ORCID：30384912, Web of Science ID：WOS:A1994MV67700004
• SELECTIVE GROWTH OF CUBIC GAN IN SMALL AREAS ON PATTERNED GAAS(100) SUBSTRATES BY METALORGANIC VAPOR-PHASE EPITAXY　　　　　　　　　　　　　　　
  M NAGAHARA; S MIYOSHI; H YAGUCHI; K ONABE; Y SHIRAKI; R ITO
  JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, Volume：33, Number：1B, First page：694, Last page：697, Jan. 1994, [Reviewed]
  The metalorganic vapor phase epitaxy growth of cubic GaN in small areas on SiO2-patterned GaAs substrates has been performed. We have succeeded in selective growth without deposition on the SiO2 mask at temperatures between 620 and 675 degrees C. The crystal quality of cubic GaN has been improved through growth in small areas on patterned GaAs substrates. It is found that the grain size becomes larger and the full width at half maximum of the X-ray diffraction peak of cubic GaN becomes narrower on patterned substrates than on unpatterned ones.
  JAPAN J APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.33.694
  DOI ID：10.1143/JJAP.33.694, ISSN：0021-4922, ORCID：30384909, Web of Science ID：WOS:A1994MV67800069
• Photoluminescence study of (111)-oriented GaAs/GaAsP strained-layer quantum well structure　　　　　　　　　　　　　　　
  Xiong Zhang; Koichi Karaki; Hiroyuki Yaguchi; Kentaro Onabe; Ryoichi Ito; Yasuhiro Shiraki
  Applied Physics Letters, Volume：64, Number：12, First page：1555, Last page：1557, 1994, [Reviewed]
  A GaAs/GaAs1-xPx (x=0.13) strained-layer quantum well structure has been grown on (111)B-oriented GaAs substrate by means of low-pressure (60 Torr) metalorganic vapor phase epitaxy and characterized by photoluminescence (PL) spectroscopy. Despite the partial relaxation of the tensile strain confined in the GaAsP barrier layers, our sample exhibits smooth surface morphology and intense optical emission. Moreover, an evident blue shift of the excitonic transition peak attributed to the screening of the strain-induced internal electric field by the photoexcited carriers, has been observed in the PL measurement.
  Scientific journal
  DOI：https://doi.org/10.1063/1.111991
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0028385086&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0028385086&origin=inward
  DOI ID：10.1063/1.111991, ISSN：0003-6951, ORCID：30384907, SCOPUS ID：0028385086, Web of Science ID：WOS:A1994NB63900032
• Characterization of Ge/SiGe strained-barrier quantum-well structures using photoreflectance spectroscopy　　　　　　　　　　　　　　　
  H. Yaguchi; K. Tai; K. Takemasa; K. Onabe; R. Ito; Y. Shiraki
  Physical Review B, Volume：49, Number：11, First page：7394, Last page：7399, 1994, [Reviewed]
  We have investigated Ge/SiGe strained-barrier quantum-well structures using photoreflectance spectroscopy. On the basis of the Γ-point transition energies associated with the Ge quantum well, the band offset at the heterojunction between Ge and SiGe has been found to vary linearly with the germanium composition in the SiGe barrier layer. The conduction-band-offset ratio Qc[=ΔEc/(ΔEc+ΔEvh)] at the Γ point is estimated to be 0.68±0.08. From the intrinsic linewidth of the quantum-well-related transitions, interface roughness has been characterized in this system and is estimated to be ±1 monolayer in our samples. © 1994 The American Physical Society.
  Scientific journal
  DOI：https://doi.org/10.1103/PhysRevB.49.7394
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0039126902&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0039126902&origin=inward
  DOI ID：10.1103/PhysRevB.49.7394, ISSN：0163-1829, ORCID：30384900, SCOPUS ID：0039126902
• Self-modulating Sb incorporation in Si/SiGe superlattices during molecular beam epitaxial growth　　　　　　　　　　　　　　　
  K. Fujita; S. Fukatsu; N. Usami; Y. Shiraki; H. Yaguchi; R. Ito; K. Nakagawa
  Surface Science, Volume：295, Number：3, First page：335, Last page：339, Oct. 1993, [Reviewed]
  Self-modulating incorporation of Sb atoms has been found in Si/SiGe superlattices grown by conventional solid source Si molecular beam epitaxy. The origin of this phenomenon has been attributed to the difference in the segregation length of Sb atoms in Si and SiGe layers. It has been found that the segregation length of Sb in Si1-xGex layers increases as the Ge composition, x, increases and that Sb atoms are incorporated mainly in Si layers when Si/SiGe superlattices are grown. © 1993.
  Scientific journal
  DOI：https://doi.org/10.1016/0039-6028(93)90280-W
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0027681891&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0027681891&origin=inward
  DOI ID：10.1016/0039-6028(93)90280-W, ISSN：0039-6028, CiNii Articles ID：80007270434, ORCID：56291770, SCOPUS ID：0027681891, Web of Science ID：WOS:A1993LZ22800011
• GAASP LAYERS GROWN ON (111)-ORIENTED GAAS SUBSTRATES BY METALORGANIC VAPOR-PHASE EPITAXY　　　　　　　　　　　　　　　
  ZHANG, X; K KARAKI; H YAGUCHI; K ONABE; Y SHIRAKI; R ITO
  JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS, Volume：32, Number：6A, First page：L755, Last page：L757, Jun. 1993, [Reviewed]
  High-quality GaAsP layers have been grown on (111)B GaAs substrates for the first time by means of low-pressure (60 Torr) metalorganic vapor phase epitaxy (MOVPE) and characterized by double-crystal X-ray diffraction and photoluminescence (PL) spectroscopy. Despite the large lattice mismatch between the GaAsP epitaxial layers and GaAs substrates, the GaAsP layers grown at higher temperature and higher V/III gas flow ratio as compared to the corresponding growth on a (100)-oriented GaAs substrate, exhibit smooth surface morphology, unambiguous X-ray diffraction peak, and intense optical emission.
  JAPAN J APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.32.L755
  DOI ID：10.1143/JJAP.32.L755, ISSN：0021-4922, ORCID：30384914, Web of Science ID：WOS:A1993LF97200001
• Metal-organic vapor phase epitaxy growth and optical study of gaas/gaas1-xpx, strained-barrier single quantum well structures　　　　　　　　　　　　　　　
  Xiong Zhang; Kentaro Onabe; Hiroyuki Yaguchi; Yasuhiro Shiraki; Ryoichi Ito
  Japanese Journal of Applied Physics, Volume：32, Number：3 B, First page：L375, Last page：L378, Mar. 1993
  GaAs/GaAs1-xPx(x = 0.15, 0.20, 0.22) single quantum wells which involve tensile-strained GaAs/GaAs1-xPxbarrier layers have been grown on GaAs substrates by metal-organic vapor phase epitaxy (MOVPE) and characterized by double-crystal X-ray diffraction, photoluminescence (PL), and Fourier-transform reflectance spectroscopy (FT- RS). Despite the relatively large relaxation ratio of the strain (sometimes as high as 7.5%), these structures exhibit smooth surface morphology as well as intense and narrow excitonic emissions. The composition-dependent energy band offset ratios for the GaAs/GaAs1-xPxstrained-barrier single quantum well structures have also been determined. © 1993 The Japan Society of Applied Physics.
  Scientific journal
  DOI：https://doi.org/10.1143/JJAP.32.L375
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=84939370422&origin=inward
  DOI ID：10.1143/JJAP.32.L375, ISSN：0021-4922, eISSN：1347-4065, SCOPUS ID：84939370422
• INTERSUBBAND ABSORPTION IN N-TYPE SI/SI1-XGEX MULTIPLE-QUANTUM-WELL STRUCTURES FORMED BY SB SEGREGANT-ASSISTED GROWTH　　　　　　　　　　　　　　　
  K FUJITA; S FUKATSU; Y SHIRAKI; H YAGUCHI; R ITO
  JOURNAL OF CRYSTAL GROWTH, Volume：127, Number：1-4, First page：416, Last page：420, Feb. 1993
  n-Si/Si1-xGex multiple quantum wells with ''abrupt'' heterointerfaces have been created by segregant-assisted growth (SAG) using Sb. Distinct well-width dependence of intersubband absorption energy in thinner quantum wells (L(z) = 14-26 angstrom) has been successfully observed. The well-width dependence of the absorption peak energy was in good agreement with a calculation based on the Kronig-Penney model where interfacial transience was taken to be shorter than than 0.4 nm. Present results show the potential power of SAG for creating ''abrupt'' Si/Si1-xGex interfaces.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/0022-0248(93)90651-C
  DOI ID：10.1016/0022-0248(93)90651-C, ISSN：0022-0248, Web of Science ID：WOS:A1993KZ45300088
• IS LOW-TEMPERATURE GROWTH THE SOLUTION TO ABRUPT SI/SI1-XGEX INTERFACE FORMATION　　　　　　　　　　　　　　　
  S FUKATSU; N USAMI; K FUJITA; H YAGUCHI; Y SHIRAKI; R ITO
  JOURNAL OF CRYSTAL GROWTH, Volume：127, Number：1-4, First page：401, Last page：405, Feb. 1993
  Si/Si1-xGex interface transients were investigated with respect to the abruptness and smoothness by using sputter depth profiling (SIMS), X-ray photoemissions (XPS), photoluminescence and transmission electron microscopy. Ge segregation was confirmed by blue-shift of luminescence energy above what is expected in a square well potential, along with SIMS measurement. Ge segregation was found to persist even at 300-degrees-C or lower. In contrast, Ge segregation was quenched by either segregant-assisted growth using Sb and Ga or solid-phase regrowth of Si cap layer; thereby a sharp Si/Si1-xGex interface was obtained. However, low-temperature-grown samples required an extensive anneal to restore band-edge luminescence, indicating a lack of quality of crystallinity.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/0022-0248(93)90648-G
  DOI ID：10.1016/0022-0248(93)90648-G, ISSN：0022-0248, Web of Science ID：WOS:A1993KZ45300085
• Highly conductive p-type cubic GaN epitaxial films on GaAs　　　　　　　　　　　　　　　
  S. Miyoshi; N. Ohkouchi; H. Yaguchi; K. Onabe; Y. Shiraki; R. Ito
  Volume：129, First page：79, Last page：84, 1993
• Characterization of Interface Roughness in Ge/SiGe Heterostructures Using Photoreflectance Spectroscopy
  Yasuhiro SHIRAKI; Keizo TAKEMASA; Ryoichi ITO; Kentaro ONABE; Kaori TAI; HIROYUKI YAGUCHI
  Extended Abstracts of the International Conference on Solid State Devices and Materials, 1993
  Scientific journal
  DOI：https://doi.org/10.7567/SSDM.1993.S-I-6-6
  DOI ID：10.7567/SSDM.1993.S-I-6-6, ORCID：56291716
• SELF-MODULATING INCORPORATION OF SB IN SI/SIGE, SUPERLATTICES DURING MOLECULAR-BEAM EPITAXIAL-GROWTH　　　　　　　　　　　　　　　
  K FUJITA; S FUKATSU; N USAMI; H YAGUCHI; Y SHIRAKI; R ITO
  SHALLOW IMPURITIES IN SEMICONDUCTORS, Volume：117, First page：159, Last page：164, 1993, [Reviewed]
  TRANS TECH PUBLICATIONS LTD, English, International conference proceedings
  DOI：https://doi.org/10.4028/www.scientific.net/MSF.117-118.159
  DOI ID：10.4028/www.scientific.net/MSF.117-118.159, ISSN：0255-5476, ORCID：30384921, Web of Science ID：WOS:A1993BZ20P00024
• PHOTOREFLECTANCE STUDY OF GAAS/GAASP STRAINED-BARRIER QUANTUM-WELL STRUCTURES　　　　　　　　　　　　　　　
  H YAGUCHI; ZHANG, X; K OTA; M NAGAHARA; K ONABE; Y SHIRAKI; R ITO
  JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS, Volume：32, Number：1B, First page：544, Last page：547, Jan. 1993, [Reviewed]
  GaAs/GaAs1-xPx strained-barrier quantum well structures grown by metalorganic vapor phase epitaxy (MOVPE) have been investigated using photoreflectance (PR) spectroscopy. On the basis of the square-potential model, we have determined the band offsets at the heterojunction and their dependence on the phosphorus composition. It was found that in the GaAs/GaAs1-xPx strained-barrier quantum well, the band offsets are almost linearly dependent on the phosphorus composition in the range of x less-than-or-equal-to 0. 23. In addition, it was derived that the conduction band offset ratio Q(c) = 0.57+/-0.05. This result is consistent with our previous study concerning GaAs/GaAsP ''strained-well'' quantum well structures.
  JAPAN J APPLIED PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.32.544
  DOI ID：10.1143/JJAP.32.544, ISSN：0021-4922, ORCID：30384920, Web of Science ID：WOS:A1993KQ00300059
• Observation of the valence-subband level crossing in GaAs/GaAsP strained-barrier quantum well structures using circularly polarized photoluminescence excitation spectroscopy　　　　　　　　　　　　　　　
  Kazunobu Ota; Hiroyuki Yaguchi; Kentaro Onabe; Ryoichi Ito; Yutaka Takahashi; Koji Muraki; Yasuhiro Shiraki
  Applied Physics Letters, Volume：63, Number：7, First page：946, Last page：948, 1993, [Reviewed]
  We have investigated the valence-subband level configuration in GaAs/GaAsP strained-barrier quantum wells as a function of the well width. As we systematically varied the well width, we observed the crossover behavior between the n=1 heavy- and light-hole states around the well width of 4 nm. Circularly polarized photoluminescence excitation (CPPLE) spectroscopy was used to identify the heavy- or light-hole character of the observed transitions. Distinct polarization properties were observed in the strain-split heavy- and light-hole states in the GaAsP barriers, which indicated that the photoexcited electrons in the barriers retained spin memory well even after the capture into the well through the relaxation process of energy and momentum. Taking advantage of this method we were able to identify unequivocally the heavy- and light-hole characters of the transitions in the quantum well. The well-width dependence of the intersubband transition energies obtained by the CPPLE measurement is in good agreement with the calculation based on the effective mass approximation.
  Scientific journal
  DOI：https://doi.org/10.1063/1.109853
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=36448998505&origin=inward
  DOI ID：10.1063/1.109853, ISSN：0003-6951, ORCID：30384919, SCOPUS ID：36448998505
• Metalorganic vapor phase epitaxy of GaP1-xNx alloys on GaP　　　　　　　　　　　　　　　
  S. Miyoshi; H. Yaguchi; K. Onabe; R. Ito; Y. Shiraki
  Applied Physics Letters, Volume：63, Number：25, First page：3506, Last page：3508, 1993, [Reviewed]
  We demonstrate a successful growth of GaP1-xNx alloys on GaP by metalorganic vapor phase epitaxy (MOVPE). This alloy system is predicted to have an extremely large miscibility gap, ranging from x=0.0000003 to 0.9999997 at 700°C. However, metastable alloys (x≤0.04) have been obtained at the growth temperature of 630-700°C. We focused on the growth condition dependence of solid composition (x). The nitrogen incorporation increases with decreasing growth temperature. It also increases with increasing growth rate, possibly due to nonequilibrium circumstances in the MOVPE growth. Low-temperature photoluminescence (PL) measurements show that the band gap of GaP1-xNx shifts to lower energy with increasing x.
  Scientific journal
  DOI：https://doi.org/10.1063/1.110109
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0346589553&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0346589553&origin=inward
  DOI ID：10.1063/1.110109, ISSN：0003-6951, ORCID：30384918, SCOPUS ID：0346589553
• MOVPE GROWTH OF CUBIC GAN ON GAAS USING DIMETHYLHYDRAZINE　　　　　　　　　　　　　　　
  S MIYOSHI; K ONABE; N OHKOUCHI; H YAGUCHI; R ITO; S FUKATSU; Y SHIRAKI
  JOURNAL OF CRYSTAL GROWTH, Volume：124, Number：1-4, First page：439, Last page：442, Nov. 1992
  High-quality cubic GaN epitaxial films have been successfully grown on (100) GaAs substrates by metalorganic vapor phase epitaxy (MOVPE) using 1,1-dimethylhydrazine (DMHy) as the nitrogen source material. The full width at half maximum (FWHM) of the X-ray diffraction profile of 0.65-degrees has been obtained, which is the narrowest reported to date. The grown films were found to be made up of ridges with (111)B facets, with increasing film thickness. Raman peak characteristic of cubic symmetry has been obtained for the first time, showing that GaN films were of excellent quality.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/0022-0248(92)90497-7
  DOI ID：10.1016/0022-0248(92)90497-7, ISSN：0022-0248, Web of Science ID：WOS:A1992KB90500070
• Initial oxidation of MBE-grown Si( 100) surfaces　　　　　　　　　　　　　　　
  Yaguchi Hiroyuki; Fujita Ken; Fukatsu Susumu; Shiraki Yasuhiro; Ito Ryoichi; Igarashi Takayuki; Hattori Takeo
  Surface Science, Volume：275, Number：3, First page：395, Last page：400, Sep. 1992
  We have investigated the initial oxidation of MBE-grown Si(100) surfaces with atomic flatness using X-ray photoemission spectroscopy (XPS) and reflection high energy electron diffraction (RHEED). It was found that the MBE-grown surfaces are inert and hardly oxidized even after exposure to molecular oxygen up to 1500 L at room temperature and that the oxygen coverage is saturated at 0.4 ML. At elevated temperatures, however, the surface oxidation was substantially promoted on the atomically flat surface. On the other hand, the oxidation was found to proceed on a deliberately corrugated Si surface prepared by a low temperature MBE growth, even at room temperature. © 1992.
  Scientific journal
  DOI：https://doi.org/10.1016/0039-6028(92)90811-J
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0026918085&origin=inward
  DOI ID：10.1016/0039-6028(92)90811-J, ISSN：0039-6028, SCOPUS ID：0026918085
• ATOMISTIC PICTURE OF INTERFACIAL MIXING IN THE SI/GE HETEROSTRUCTURES　　　　　　　　　　　　　　　
  S FUKATSU; K FUJITA; H YAGUCHI; Y SHIRAKI; R ITO
  SURFACE SCIENCE, Volume：267, Number：1-3, First page：79, Last page：82, Apr. 1992
  Atomistic description of the interfacial mixing in the Si/Ge heterostructures during molecular beam epitaxial growth is presented. It is shown that the surface segregation of Ge atoms at the Si/Ge heterointerface is self-limited, i.e. controlled by Ge themselves, when their concentration is higher than 0.01 monolayer, due to the geometrical constraint arising from the surface bonding. In consequence, the Ge segregation exhibits a nonlinear behavior, which produces a non-exponential segregation profile. The Ge segregation is found to undergo a transition from a kinetically limited to an equilibrium regime around 400-degrees-C at a growth rate of 0.1 nm/s.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/0039-6028(92)91093-Q
  DOI ID：10.1016/0039-6028(92)91093-Q, ISSN：0039-6028, Web of Science ID：WOS:A1992HM90100022
• Photoreflectance Study of GaAs/GaAsP Strained-Barrier Quantum Well Structures　　　　　　　　　　　　　　　
  Hiroyuki YAGUCHI; Xiong ZHANG; Kentaro ONABE; Yasuhiro SHIRAKI; Ryoichi ITO
  Extended Abstracts of the 1992 International Conference on Solid State Devices and Materials, First page：589, Last page：591, 1992, [Reviewed]
  GaAsP strained-layer quantum well structures grown by metalorganic vapor phase epitaxy have been investigated using photoreflectance spectroscopy. We have focused our attention on GaAs/GaAsP 'strained-barrier' quantum well structures on GaAs(100) substrates. We have determined the band offset at the heterojunction and its dependence on the phosphorus composition. It was found that the band offsets are almost linearly dependent on the phosphorus composition in the range of x ≤ 0.23. In addition, it was derived that the conduction band offset ratio Qc = 0.57 ± 0.05.
  The Japan Society of Applied Physics, English, International conference proceedings
  DOI：https://doi.org/10.7567/ssdm.1992.b-4-5
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0027002314&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0027002314&origin=inward
  DOI ID：10.7567/ssdm.1992.b-4-5, SCOPUS ID：0027002314
• Intersubbband absorption in narrow Si/SiGe multiple quantum wells without interfacial smearing　　　　　　　　　　　　　　　
  K. Fujita; S. Fukatsu; Y. Shiraki; H. Yaguchi; R. Ito
  Applied Physics Letters, Volume：61, Number：2, First page：210, Last page：212, 1992, [Reviewed]
  Si/Si1-xGex multiple quantum wells with abrupt heterointerfaces have been formed by segregant-assisted growth (SAG) with Sb. Distinct well-width dependence of intersubband absorption in the narrow quantum wells has been observed. The well-width dependence of the absorption peak energy is in good agreement with a calculation based on the Kronig-Penney model where interfacial smearing is taken to be less than 0.4 nm, suggesting the integrity of Si/Si1-xGex interfaces grown by SAG.
  English, Scientific journal
  DOI：https://doi.org/10.1063/1.108220
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0346609110&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0346609110&origin=inward
  DOI ID：10.1063/1.108220, ISSN：0003-6951, ORCID：30384925, SCOPUS ID：0346609110
• Strain relaxation in MBE-grown Si1-xGex/Si(100) heterostructures by annealing　　　　　　　　　　　　　　　
  Hiroyuki Yaguchi; Ken Fujita; Susumu Fukatsu; Yasuhiro Shiraki; Ryoichi Ito
  Japanese Journal of Applied Physics, Part 2: Letters, Volume：30, Number：8 B, First page：L1450, Last page：L1453, 1991, [Reviewed]
  Strain relaxation in MBE-grown Si1-xGex/Si(100) strained-layer heterostructures by postgrowth annealing has been investigated using X-ray diffraction and Nomarski microscopy. The extent of the strain relaxation is found to be dependent on Ge composition and annealing temperatures. The strain relaxation model proposed by Dodson and Tsao is applied to our experimental data and good agreement is obtained.
  English, Scientific journal
  DOI：https://doi.org/10.1143/JJAP.30.L1450
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0026207085&origin=inward
  DOI ID：10.1143/JJAP.30.L1450, ISSN：0021-4922, ORCID：30384929, SCOPUS ID：0026207085
• Self-limitation in the surface segregation of Ge atoms during Si molecular beam epitaxial growth　　　　　　　　　　　　　　　
  S. Fukatsu; K. Fujita; H. Yaguchi; Y. Shiraki; R. Ito
  Applied Physics Letters, Volume：59, Number：17, First page：2103, Last page：2105, 1991, [Reviewed]
  Self-limitation in the surface segregation of Ge atoms in the Si epitaxial overlayers arising from the surface bond geometry on Si(100) during molecular beam epitaxy has been investigated theoretically. It was found that Ge surface segregation is strongly limiting when the Ge concentration exceeds 0.01 monolayer. As a result of this self-limitation, segregation profiles of Ge in Si overlayers are found to decay nonexponentially in the growth direction with a kink in the profile around 3×1020 cm-3, which is in close agreement with the experimental observation. The kinetic barrier of the Ge surface segregation is estimated to be 1.63±0.1 eV.
  Scientific journal
  DOI：https://doi.org/10.1063/1.106412
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=36449004565&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=36449004565&origin=inward
  DOI ID：10.1063/1.106412, ISSN：0003-6951, ORCID：30384928, SCOPUS ID：36449004565
• Involvement of the topmost Ge layer in the Ge surface segregation during Si/Ge heterostructure formation　　　　　　　　　　　　　　　
  K. Fujita; S. Fukatsu; H. Yaguchi; Y. Shiraki; R. Ito
  Applied Physics Letters, Volume：59, Number：18, First page：2240, Last page：2241, 1991, [Reviewed]
  Surface segregation of Ge atoms during Si/Ge heterostructure formation by molecular beam epitaxy has been investigated by x-ray photoemission spectroscopy varying the Ge layer thickness. It has been found that only the Ge atoms of the topmost layer are involved in the surface segregation, leaving the rest of the Ge atoms intact. This result supports the basic idea of the two-state-exchange model.
  English, Scientific journal
  DOI：https://doi.org/10.1063/1.106082
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=36449002825&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=36449002825&origin=inward
  DOI ID：10.1063/1.106082, ISSN：0003-6951, ORCID：30384927, SCOPUS ID：36449002825
• Realization of Abrupt interfaces in Si/Ge superlattices by suppressing Ge Surface Segregation with infmonolayer of Sb　　　　　　　　　　　　　　　
  Ken Fujita; Susumu Fukatsu; Hiroyuki Yaguchi; Takayuki Igarashi; Yasuhiro Shiraki; Ryoichi Ito
  Japanese Journal of Applied Physics, Volume：29, Number：11, First page：L1981, Last page：L1983, Nov. 1990
  Atomic mixing in Si/Ge strained-layer superlattices is investigated by means of SiMS and XPS. The interfacial mixing is attributed to the surface segregation of Ge atoms during MBE growth of Si overlayers. it is demonstrated that the surface segregation is remarkably suppressed by depositing infmonolayer Sb atoms on Ge layers prior to Si overgrowth and that Ge layers are confined to within 0.8 nm. © 1990 IOP Publishing Ltd.
  Scientific journal
  DOI：https://doi.org/10.1143/JJAP.29.L1981
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=3743115953&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=3743115953&origin=inward
  DOI ID：10.1143/JJAP.29.L1981, ISSN：0021-4922, eISSN：1347-4065, SCOPUS ID：3743115953
• Suppression of Interfacial Mixing in Si/Ge Superlattices by Sb Deposition　　　　　　　　　　　　　　　
  K. FUJITA; S. FUKATSU; H. YAGUCHI; T. IGARASHI; Y. SHIRAKI; R. ITO
  Extended Abstracts of the 1990 International Conference on Solid State Devices and Materials, First page：1151, Last page：1152, 1990, [Reviewed]
  Atomic mixing at Si/Ge interfaces in strained layer superlattices (SLS's) is investigated by means of SIMS and XPS. The interfacial mixing is attributed to surface segregation of Ge atoms on which Si layer is commensurately grown during MBE. It is demonstrated that the surface segregation is remarkably supressed by depositing submonolayer Sb atoms on Ge layers before Si overgrowth and that Ge layers are revealed to be confined to within 0.8nm.
  The Japan Society of Applied Physics, English, International conference proceedings
  DOI：https://doi.org/10.7567/ssdm.1990.ln-d-1
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0025554961&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0025554961&origin=inward
  DOI ID：10.7567/ssdm.1990.ln-d-1, SCOPUS ID：0025554961
• RHEED study of superstructures of submonolayer lead films on silicon (111) surfaces　　　　　　　　　　　　　　　
  H. Yaguchi; S. Baba; A. Kinbara
  Applied Surface Science, Volume：33-34, Number：C, First page：75, Last page：80, Sep. 1988, [Reviewed]
  Coverage and temperature dependences of Pb/Si(111) surface structure have been investigated using reflection high energy electron diffraction (RHEED) and molecular beam deposition techniques. With the deposition of Pb on a clean Si(111) surface in the temperature range between 30 and 500 ° C, sequential changes in the RHEED pattern were observed in situ and thus a phase diagram of superstructures of submonolayer lead films on Si(111) surface could be established. © 1988.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/0169-4332(88)90290-5
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0024067915&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0024067915&origin=inward
  DOI ID：10.1016/0169-4332(88)90290-5, ISSN：0169-4332, CiNii Articles ID：80004251511, ORCID：30384931, SCOPUS ID：0024067915, Web of Science ID：WOS:A1988Q431500011
• Pb/Si(111)表面超構造のRHEEDによる観察　　　　　　　　　　　　　　　
  H. Yaguchi; S. Baba; A. Kinbara
  表面科学, Volume：9, Number：5, First page：368, Last page：373, 1988
  Scientific journal
  DOI：https://doi.org/10.1380/jsssj.9.368
  DOI ID：10.1380/jsssj.9.368, ISSN：0388-5321, CiNii Articles ID：80004300663, ORCID：79735519
• RHEED study of Pb/Si(111) surface superstructures.　　　　　　　　　　　　　　　
  Hiroyuki YAGUCHI; Shigeru BABA; Akira KINBARA
  SHINKU, Volume：31, Number：5, First page：399, Last page：401, 1988, [Reviewed]
  The Vacuum Society of Japan, Japanese, Scientific journal
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85024451098&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85024451098&origin=inward
  DOI ID：10.3131/jvsj.31.399, ISSN：0559-8516, eISSN：1880-9413, CiNii Articles ID：130000863491, CiNii Books ID：AN00119871, ORCID：79735477, SCOPUS ID：85024451098

• Recent Progress of 230 nm AlGaN far-UVC LED on sapphire substrate　　　　　　　　　　　　　　　
  平山秀樹; KHAN Ajmal Muhammad; 鹿嶋行雄; 松浦恵理子; 前田哲利; 牟田実広; 大神裕之; 毛利健吾; 河島宏和; 祝迫恭; 藤川紗千恵; 矢口裕之
  Optronics, Number：509, 2024
  ISSN：0286-9659, J-Global ID：202402241195880802
• 輝きと魅力を増す最近の光源 生体無害ウイルス不活化を目指した230nm帯高出力far-UVC LEDの進展　　　　　　　　　　　　　　　
  平山秀樹; KHAN Ajmal Muhammad; 鹿嶋行雄; 松浦恵理子; 前田哲利; 牟田実広; 大神裕之; 祝迫恭; 藤川紗千恵; 矢口裕之
  Volume：35, Number：7, 2024
  ISSN：0917-026X, J-Global ID：202402249015186556
• Dependence of emission efficiency of 230 nm AlGaN far-UVC LED on quantum well structure　　　　　　　　　　　　　　　
  永田裕弥; 永田裕弥; 仲元寺郁弥; 仲元寺郁弥; 前田哲利; 藤川紗千恵; 藤川紗千恵; 矢口裕之; 祝迫恭; 平山秀樹
  応用物理学会秋季学術講演会講演予稿集(CD-ROM), Volume：84th, 2023
  ISSN：2758-4704, J-Global ID：202402213347263220
• Study on the Binding Energy of Biexcitons Localized at Isoelectronic Traps in Nitrogen δ-Doped GaAs　　　　　　　　　　　　　　　
  矢野裕子; 高宮健吾; 藤川沙千恵; 八木修平; 矢口裕之; 小林真隆; 秋山英文
  応用物理学会春季学術講演会講演予稿集(CD-ROM), Volume：70th, 2023
  ISSN：2436-7613, J-Global ID：202302286333664872
• Development of Shorter Wavelength 230 nm-Band Far-UVC LEDs and Realization of High Output Power LED Panels　　　　　　　　　　　　　　　
  牟田実広; 大神裕之; 毛利健吾; 河島宏和; 前田哲利; KHAN Ajmal; 鹿嶋行雄; 松浦恵里子; 中村祐樹; 住司光; 桐原大河; 藤川紗千恵; 矢口裕之; 祝迫恭; 平山秀樹
  電子情報通信学会技術研究報告(Web), Volume：123, Number：288(ED2023 14-37), 2023
  ISSN：2432-6380, J-Global ID：202402226864927084
• Excitation Power Dependence of Emission Lines from Er Doped GaAs　　　　　　　　　　　　　　　
  伊藤駿平; 高宮健吾; 小林真隆; 八木修平; 秋山英文; 矢口裕之
  応用物理学会春季学術講演会講演予稿集(CD-ROM), Volume：69th, 2022
  ISSN：2436-7613, J-Global ID：202202243673645430
• Progress of UVC-LEDs using DC sputter AlN templates　　　　　　　　　　　　　　　
  最上耀介; 最上耀介; 大澤篤史; 尾崎一人; 谷岡千丈; 前岡淳史; 糸数雄吏; 糸数雄吏; 桑葉俊輔; 桑葉俊輔; 定昌史; 前田哲利; 矢口裕之; 平山秀樹
  電子情報通信学会技術研究報告, Volume：119, Number：304(LQE2019 76-101), 2019
  ISSN：0913-5685, J-Global ID：202002288409055443
• 有機鉛ペロブスカイト製膜過程リアルタイム観察　　　　　　　　　　　　　　　
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  Volume：66th, 2019
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• 第一原理計算によるGaAsN混晶中のN原子配置のバンド構造への影響の検討
  塚原悠太; 八木修平; 矢口裕之
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  Japanese
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• 二波長励起PL測定によるGaPN混晶のアップコンバージョン発光特性評価
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  J-Global ID：201802238518840151
• 規則配列化InNドットの作製に向けた立方晶GaN表面ステップ構造の成長条件依存性
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  J-Global ID：201802262792771299
• RF‐MBE成長による4H‐SiC(000-1)基板上へのN極性GaNの作製
  杉浦亮; 高宮健吾; 八木修平; 矢口裕之
  応用物理学会秋季学術講演会講演予稿集(CD-ROM), Volume：79th, First page：ROMBUNNO.19p‐PA4‐14, Sep. 2018
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  J-Global ID：201802290158483556
• MBE成長したErドープGaAsの発光特性に対するアニーリングの影響
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  J-Global ID：201802217506237741
• 真空プロセスによる有機鉛ペロブスカイトの結晶成長制御　　　　　　　　　　　　　　　
  宮寺哲彦; 阿内悠人; 小金澤智之; 矢口裕之; 吉田郵司; 近松真之
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• Investigation of SiC/Oxide Interface Structures by Spectroscopic Ellipsometry　　　　　　　　　　　　　　　
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  {InTech}
  DOI：https://doi.org/10.5772/61082
  DOI ID：10.5772/61082, ORCID put code：79779725
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  J-Global ID：201502207598351728
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• 円偏光PLEによるGe直接遷移端への光スピン注入
  安武裕輔; 安武裕輔; 太野垣健; 太野垣健; 大川洋平; 矢口裕之; 金光義彦; 深津晋
  応用物理学会秋季学術講演会講演予稿集(CD-ROM), Volume：76th, First page：ROMBUNNO.14A-2N-8, 31 Aug. 2015
  Japanese
  J-Global ID：201502209609017925
• GaAs:Nδドープ超格子を有する太陽電池の二段階光吸収
  鈴木智也; 八木修平; 土方泰斗; 岡田至崇; 矢口裕之
  応用物理学会春季学術講演会講演予稿集(CD-ROM), Volume：62nd, First page：ROMBUNNO.13P-P19-17, 26 Feb. 2015
  Japanese
  J-Global ID：201502212728546006
• 4H‐SiC(0001)微傾斜基板を用いたInNドット配列の自己形成
  森誠也; 高宮健吾; 折原操; 八木修平; 土方泰斗; 矢口裕之
  応用物理学会春季学術講演会講演予稿集(CD-ROM), Volume：62nd, First page：ROMBUNNO.12P-P16-9, 26 Feb. 2015
  Japanese
  J-Global ID：201502237562705111
• 第一原理計算によるInAsN混晶のバンド構造に関する研究
  宮崎貴史; 八木修平; 土方泰斗; 矢口裕之
  応用物理学会春季学術講演会講演予稿集(CD-ROM), Volume：62nd, First page：ROMBUNNO.13A-P15-2, 26 Feb. 2015
  Japanese
  J-Global ID：201502238490747422
• 添加剤導入によるP3HT:PCBM混合膜の結晶成長過程のその場観察評価　　　　　　　　　　　　　　　
  新井康司; 新井康司; 柴田陽生; 伊藤英輔; 小金澤智之; 宮寺哲彦; 宮寺哲彦; 近松真之; 矢口裕之
  Volume：62nd, 2015
  J-Global ID：201502277517255255
• 中間バンド型太陽電池に向けたGaAs:Nδドープ超格子のMBE成長
  鈴木智也; 長田一輝; 八木修平; 内藤駿弥; 土方泰斗; 岡田至崇; 矢口裕之
  応用物理学会秋季学術講演会講演予稿集(CD-ROM), Volume：75th, First page：ROMBUNNO.19P-PB3-10, 01 Sep. 2014
  Japanese
  J-Global ID：201402204873316264
• SiC酸化へのArアニール導入による酸化膜成長速度の変化
  今野良太郎; 八木修平; 土方泰斗; 矢口裕之
  応用物理学会秋季学術講演会講演予稿集(CD-ROM), Volume：75th, First page：ROMBUNNO.19A-PB5-11, 01 Sep. 2014
  Japanese
  J-Global ID：201402218643252926
• GaAs:Nδドープ超格子による中間バンド構造のエネルギー制御
  長田一輝; 鈴木智也; 八木修平; 内藤駿弥; 庄司靖; 岡田至崇; 土方泰斗; 矢口裕之
  応用物理学会秋季学術講演会講演予稿集(CD-ROM), Volume：75th, First page：ROMBUNNO.19A-S1-6, 01 Sep. 2014
  Japanese
  J-Global ID：201402223396439019
• Geの磁場中時間分解円偏光フォトルミネッセンス
  安武裕輔; 矢口裕之; 深津晋
  応用物理学会秋季学術講演会講演予稿集(CD-ROM), Volume：75th, First page：ROMBUNNO.17P-PA3-7, 01 Sep. 2014
  Japanese
  J-Global ID：201402279887395531
• RF‐MBE法によるGaAs(110)基板上へのGaNの成長
  五十嵐健; 折原操; 八木修平; 土方泰斗; 窪谷茂幸; 片山竜二; 矢口裕之
  応用物理学会春季学術講演会講演予稿集(CD-ROM), Volume：61st, First page：ROMBUNNO.20A-PG1-15, 03 Mar. 2014
  Japanese
  J-Global ID：201402228659986330
• 二波長励起PLによるGaPN混晶の光学特性評価
  末次麻希子; TOUHIDUL ISLAM A.Z.M; 花岡司; 福田武司; 鎌田憲彦; 八木修平; 矢口裕之
  照明学会全国大会講演論文集(CD-ROM), Volume：47th, First page：ROMBUNNO.10-3, 2014
  Japanese
  J-Global ID：201402295481095788
• 六方晶SiC無極性面の酸化過程の実時間観察
  後藤大祐; 八木修平; 土方泰斗; 矢口裕之
  応用物理学会秋季学術講演会講演予稿集(CD-ROM), Volume：74th, First page：ROMBUNNO.19A-P9-4, 31 Aug. 2013
  Japanese
  J-Global ID：201302203339195393
• 窒素δドープGaAs中の単一等電子トラップによる励起子分子発光の時間分解フォトルミネッセンス測定
  高宮健吾; 八木修平; 土方泰斗; 望月敏光; 吉田正裕; 秋山英文; 窪谷茂幸; 片山竜二; 尾鍋研太郎; 矢口裕之
  応用物理学会秋季学術講演会講演予稿集(CD-ROM), Volume：74th, First page：ROMBUNNO.19A-P8-11, 31 Aug. 2013
  Japanese
  J-Global ID：201302208930844769
• GaInNAs量子井戸の発光効率へのレーザー照射の影響
  岩崎卓也; 八木修平; 土方泰斗; 上田修; 矢口裕之
  応用物理学会秋季学術講演会講演予稿集(CD-ROM), Volume：74th, First page：ROMBUNNO.19A-P8-13, 31 Aug. 2013
  Japanese
  J-Global ID：201302210710989914
• GaAsN/GaAs量子井戸構造からの発光の励起強度依存性
  山崎泰由; 八木修平; 土方泰斗; 尾鍋研太郎; 矢口裕之
  応用物理学会秋季学術講演会講演予稿集(CD-ROM), Volume：74th, First page：ROMBUNNO.19A-P8-14, 31 Aug. 2013
  Japanese
  J-Global ID：201302253457891105
• GaAs:Nδドープ超格子を用いた中間バンド型太陽電池の特性評価
  八木修平; 野口駿介; 土方泰斗; 窪谷茂幸; 尾鍋研太郎; 岡田至崇; 矢口裕之
  応用物理学会秋季学術講演会講演予稿集(CD-ROM), Volume：74th, First page：ROMBUNNO.17P-D6-14, 31 Aug. 2013
  Japanese
  J-Global ID：201302263267421817
• InN/GaNドット多重積層構造に向けたGaNキャップ層成長条件の検討　　　　　　　　　　　　　　　
  徳田英俊; 折原操; 八木修平; 土方泰斗; 矢口裕之
  応用物理学会秋季学術講演会講演予稿集(CD-ROM), Volume：74th, Number：8, First page：ROMBUNNO.17P-P7-15, Last page：08JL06-4, 31 Aug. 2013
  Creation of short-period InN/GaN superlattices is one of the possible ways of conducting band gap engineering in the green-blue range of the spectrum. The present paper reports results of photoluminescence experiments, including pressure effects, on a superlattice sample consisting of unit cells with one monolayer of InN and 40 monolayers of GaN. The results are compared with calculations performed for different types of superlattices: InN/GaN, InGaN/GaN, and InN/InGaN/GaN with single monolayers of InN and/or InGaN. The superlattices are simulated by band structure calculations based on the local density approximation (LDA) with a semi-empirical correction for the ``LDA gap error''. A similarity is observed between the results of calculations for an InGaN/GaN superlattice (with one monolayer of InGaN) and the experimental results. This indicates that the fabricated InN quantum wells may contain some Ga atoms due to interdiffusion.
  The Japan Society of Applied Physics, Japanese
  DOI：https://doi.org/10.7567/JJAP.52.08JL06
  DOI ID：10.7567/JJAP.52.08JL06, ISSN：0021-4922, J-Global ID：201302285385764625, CiNii Articles ID：40019758965, CiNii Books ID：AA12295836
• Ge/SiGe多重量子井戸への室温光スピン注入
  安武裕輔; 矢口裕之; 深津晋
  応用物理学会秋季学術講演会講演予稿集(CD-ROM), Volume：74th, First page：ROMBUNNO.16P-C15-3, 31 Aug. 2013
  Japanese
  J-Global ID：201302231556794835
• An attempt for clarification of SiC oxidation mechanism : Common/different point to Si oxidation　　　　　　　　　　　　　　　
  HIJIKATA Yasuto; YAGI Shuhei; YAGUCHI Hiroyuki
  Technical report of IEICE. SDM, Volume：113, Number：87, First page：91, Last page：96, 18 Jun. 2013
  Further understanding of the SiC oxidization mechanism is indispensable for MOSFET using a SiC semiconductor to exceed the conventional Si-based power devices. In this report, we summarize what have been found so far about the oxidization mechanism of SiC, and the research tendency and its subjects in recent years are introduced in terms of common or difference against Si oxidization.
  The Institute of Electronics, Information and Communication Engineers, Japanese
  ISSN：0913-5685, CiNii Articles ID：110009779110, CiNii Books ID：AN10013254
• RF‐MBE法による立方晶InNドット積層構造の作製
  鈴木潤一郎; 折原操; 八木修平; 土方泰斗; 矢口裕之
  応用物理学会春季学術講演会講演予稿集(CD-ROM), Volume：60th, First page：ROMBUNNO.28P-PA1-1, 11 Mar. 2013
  Japanese
  J-Global ID：201302223183186110
• 4H‐SiCエピ膜中積層欠陥への熱酸化の影響について
  宮野祐太郎; 八木修平; 土方泰斗; 矢口裕之
  応用物理学会春季学術講演会講演予稿集(CD-ROM), Volume：60th, First page：ROMBUNNO.29P-PB4-9, 11 Mar. 2013
  Japanese
  J-Global ID：201302267568241755
• 中間バンド型太陽電池へ向けたGaAs中窒素ドープ超格子のE₊バンド光吸収の観測
  野口駿介; 八木修平; 土方泰斗; 窪谷茂幸; 岡田至崇; 尾鍋研太郎; 矢口裕之
  応用物理学会春季学術講演会講演予稿集(CD-ROM), Volume：60th, First page：ROMBUNNO.29A-PB7-19, 11 Mar. 2013
  Japanese
  J-Global ID：201302299241158730
• Thermal Oxidation Mechanism of Silicon Carbide　　　　　　　　　　　　　　　
  Yasuto Hijikata; Shuhei Yagi; Hiroyuki Yaguchi; Sadafumi Yoshi
  Physics and Technology of Silicon Carbide Devices, Oct. 2012
  {InTech}
  DOI：https://doi.org/10.5772/50748
  DOI ID：10.5772/50748, ORCID put code：79780638
• Nondestructive and Contactless Characterization Method for Spatial Mapping of the Thickness and Electrical Properties in Homo-Epitaxially Grown SiC Epilayers Using Infrared Reflectance Spectroscopy　　　　　　　　　　　　　　　
  Sadafumi Yoshida; Yasuto Hijikata; Hiroyuki Yaguchi
  Physics and Technology of Silicon Carbide Devices, Oct. 2012
  {InTech}
  DOI：https://doi.org/10.5772/50749
  DOI ID：10.5772/50749, ORCID put code：79780627
• スパッタ薄膜成長による4H‐SiC基板中の非発光再結合中心生成
  加藤寿悠; 八木修平; 土方泰斗; 矢口裕之
  応用物理学会学術講演会講演予稿集(CD-ROM), Volume：73rd, First page：ROMBUNNO.11P-PB2-12, 27 Aug. 2012
  Japanese
  J-Global ID：201202222514720266
• 堆積と熱酸化による4H‐SiC MOS構造の作製
  大谷篤志; 八木修平; 土方泰斗; 矢口裕之
  応用物理学会学術講演会講演予稿集(CD-ROM), Volume：73rd, First page：ROMBUNNO.11P-PB2-4, 27 Aug. 2012
  Japanese
  J-Global ID：201202230425306688
• InN成長におけるInN高温バッファ層の効果に関する検討
  増田篤; 折原操; 八木修平; 土方泰斗; 矢口裕之
  応用物理学会学術講演会講演予稿集(CD-ROM), Volume：73rd, First page：ROMBUNNO.12A-PB4-11, 27 Aug. 2012
  Japanese
  J-Global ID：201202235572897960
• 第一原理計算によるGaAsNの電子構造に対する原子配置の影響に関する研究
  坂本圭; 八木修平; 土方泰斗; 矢口裕之
  応用物理学会学術講演会講演予稿集(CD-ROM), Volume：73rd, First page：ROMBUNNO.12A-PB4-22, 27 Aug. 2012
  Japanese
  J-Global ID：201202252900504833
• 窒素δドープGaAs中の単一等電子トラップからの発光のフォトルミネッセンス励起分光測定
  高宮健吾; 八木修平; 土方泰斗; 望月敏光; 吉田正裕; 秋山英文; 窪谷茂幸; 尾鍋研太郎; 片山竜二; 矢口裕之
  応用物理学会学術講演会講演予稿集(CD-ROM), Volume：73rd, First page：ROMBUNNO.12P-PB11-20, 27 Aug. 2012
  Japanese
  J-Global ID：201202257209482469
• MBE法によるGaAs(001)基板上へのErGaAs混晶の成長
  JIN R; 八木修平; 土方泰斗; 窪谷茂幸; 尾鍋研太郎; 片山竜二; 矢口裕之
  応用物理学会学術講演会講演予稿集(CD-ROM), Volume：73rd, First page：ROMBUNNO.12P-PB11-16, 27 Aug. 2012
  Japanese
  J-Global ID：201202271314197829
• RF‐MBE法によるGaAs(110)基板上への半極性InN成長に対する窒化の影響
  五十嵐健; 折原操; 八木修平; 土方泰斗; 矢口裕之
  応用物理学会学術講演会講演予稿集(CD-ROM), Volume：73rd, First page：ROMBUNNO.12A-PB4-12, 27 Aug. 2012
  Japanese
  J-Global ID：201202279081759741
• RF‐MBE法によるTiO₂(001)基板上への立方晶GaNの成長
  折原操; 八木修平; 土方泰斗; 矢口裕之
  応用物理学会学術講演会講演予稿集(CD-ROM), Volume：73rd, First page：ROMBUNNO.13P-H9-17, 27 Aug. 2012
  Japanese
  J-Global ID：201202285680090400
• 熱酸化が4H‐SiCエピ膜中積層欠陥に及ぼす影響の顕微フォトルミネッセンスによる観察
  山形光; 八木修平; 土方泰斗; 矢口裕之
  応用物理学関係連合講演会講演予稿集(CD-ROM), Volume：59th, First page：ROMBUNNO.17P-A8-11, 29 Feb. 2012
  Japanese
  J-Global ID：201202246861327481
• 窒素δドープGaAsにおける単一等電子トラップからの励起子分子発光
  高宮健吾; 福島俊之; 星野真也; 八木修平; 土方泰斗; 望月敏光; 吉田正裕; 秋山英文; 窪谷茂幸; 尾鍋研太郎; 片山竜二; 矢口裕之
  応用物理学関係連合講演会講演予稿集(CD-ROM), Volume：59th, First page：ROMBUNNO.17A-A8-9, 29 Feb. 2012
  Japanese
  J-Global ID：201202254067781707
• 分光エリプソメトリによる立方晶InNの光学的特性評価
  吉田倫大; 折原操; 八木修平; 土方泰斗; 矢口裕之
  応用物理学関係連合講演会講演予稿集(CD-ROM), Volume：59th, First page：ROMBUNNO.16A-DP1-27, 29 Feb. 2012
  Japanese
  J-Global ID：201202270422534312
• GaAs中窒素δドープ超格子のエネルギー構造評価
  野口駿介; 八木修平; 土方泰斗; 窪谷茂幸; 尾鍋研太郎; 矢口裕之
  応用物理学関係連合講演会講演予稿集(CD-ROM), Volume：59th, First page：ROMBUNNO.17P-DP3-12, 29 Feb. 2012
  Japanese
  J-Global ID：201202272956548214
• 窒素δドープGaAs中の窒素原子対が形成する単一の等電子トラップからの発光に対する一軸応力の影響
  新井佑也; 星野真也; 高宮健吾; 八木修平; 土方泰斗; 望月敏光; 吉田正裕; 秋山英文; 窪谷茂幸; 尾鍋研太郎; 矢口裕之
  応用物理学関係連合講演会講演予稿集(CD-ROM), Volume：59th, First page：ROMBUNNO.17P-DP3-13, 29 Feb. 2012
  Japanese
  J-Global ID：201202279946154581
• 共鳴トンネル構造を用いたエネルギー選択層における熱励起電流のホットキャリア型太陽電池特性への影響
  八木修平; 土方泰斗; 岡田至崇; 矢口裕之
  応用物理学会学術講演会講演予稿集(CD-ROM), Volume：72nd, First page：ROMBUNNO.1A-H-12, 16 Aug. 2011
  Japanese
  J-Global ID：201102252261232919
• Growth rate enhancement of silicon-carbide oxidation in thin oxide regime　　　　　　　　　　　　　　　
  Hijikata Yasuto; Yaguchi Hiroyuki; Yoshida Sadafumi; Gerhardt R
  Properties and Applications of Silicon Carbide, First page：77, Last page：87, 2011, [Reviewed]
  DOI：https://doi.org/10.5772/14591
  DOI ID：10.5772/14591, ORCID put code：30384781, Web of Science ID：WOS:000363729000005
• 極低窒素濃度GaAsNのフォトリフレクタンススペクトル
  大久保航; 石川輝; 八木修平; 土方泰斗; 吉田貞史; 片山竜二; 尾鍋研太郎; 矢口裕之
  応用物理学会学術講演会講演予稿集(CD-ROM), Volume：71st, First page：ROMBUNNO.14P-ZV-1, 30 Aug. 2010
  Japanese
  J-Global ID：201002208945322457
• 極低窒素濃度GaAsN中の等電子トラップからの発光に対する一軸応力の影響
  新井佑也; 遠藤雄太; 八木修平; 土方泰斗; 窪谷茂幸; 尾鍋研太郎; 片山竜二; 矢口裕之
  応用物理学会学術講演会講演予稿集(CD-ROM), Volume：71st, First page：ROMBUNNO.14P-ZV-2, 30 Aug. 2010
  Japanese
  J-Global ID：201002211648568235
• 酸化中のSiC層へのSiおよびC原子放出についての理論的検討
  土方泰斗; 八木修平; 矢口裕之; 吉田貞史
  応用物理学会学術講演会講演予稿集(CD-ROM), Volume：71st, First page：ROMBUNNO.15A-ZS-10, 30 Aug. 2010
  Japanese
  J-Global ID：201002219694574542
• Theoretical studies for Si and C emission into SiC layer during oxidation　　　　　　　　　　　　　　　
  土方 泰斗; 矢口 裕之; 吉田 貞史
  埼玉大学工学部紀要 第一部 論文集, Volume：44, First page：34, Last page：37, 2010
  To understand the structure of SiC-oxide interface more in detail, we propose a theory for calculating the depth profiles of Si and C emitted into SiC layer during oxidation. Simulations of the depth profiles of Si and C interstitials results in the structures analogous with those observed from a spectroscopic ellipsometry. To determine the diffusivities of Si and C interstitials, we performed capacitance-voltage measurements for examining the re-distribution profiles of nitrogen after oxidation. By comparing between observed and calculated profile, we obtained the self-diffusivity of C interstitials and confirmed that the proposed theory was appropriate to estimate depth profiles of Si and C interstitials emitted into SiC layer.
  埼玉大学工学部広報委員会, Japanese
  ISSN：1880-4446, CiNii Articles ID：120005386082
• Characterization of oxidizing interface and elucidation of oxidation mechanism of SiC semiconductor using spectroscopic ellipsometry　　　　　　　　　　　　　　　
  土方 泰斗; 矢口 裕之; 吉田 貞史
  埼玉大学工学部紀要 第一部 論文集, Volume：43, First page：17, Last page：21, 2009
  We tried to elucidate the oxidizing interface structure of SiC semiconductor and its oxidation mechanism. First of all, we investigated the analysis method for deriving the thickness of interface layer and verified the validity of the method by analyzing the multi-angle measurement data. As a result of analysis for SiC-oxide interfaces using the analysis method, it is found that the photon energy dispersion of optical constants of the interface layer is similar to that for SiC, the real part of dielectric function is larger than that of SiC, and the imaginary part agrees with that of SiC. In addition, we examined the thickness dependence of optical constants of interface layer and found that the standing point in energy dispersion of the imaginary part of dielectric function shifted to the lower energy-side at 40 nm of oxide thickness. In addition to the observation of SiC-oxide interface, real-time measurements of oxide growth-rates of SiC at various oxidation temperatures were conducted using an in-situ spectroscopic ellipsometer. We tried to apply 'Si and C emission model', which is proposed as the SiC oxidation model by us, to the experimental growth-rate data. As a result, the Si and C emission model well reproduced the growth-rate at the entire oxide thickness region at all of the oxidation temperatures measured for both of (0001)Si-face and (000-1)C-face. Based on the knowledge on oxidizing interface layer and oxidation mechanism obtained from spectroscopic ellipsometry studies, we discuss the structure of interface layer and the formation mechanism of interface states.
  埼玉大学工学部, Japanese
  CiNii Articles ID：120005386070
• RF-MBE法を用いた3C-SiC基板上への立方晶InNの結晶成長およびその物性評価　　　　　　　　　　　　　　　
  富田康浩; 井上赳; 折原操; 土方泰斗; 矢口裕之; 吉田貞史; 平林康男
  Volume：55th, Number：1, 2008
  J-Global ID：200902203029436754
• Single photon emission from locally doped semiconductors
  矢口 裕之
  旭硝子財団助成研究成果報告, First page：1, Last page：7, 2008
  旭硝子財団, Japanese
  ISSN：1882-0069, CiNii Articles ID：40019970578
• 閃亜鉛鉱構造窒化物半導体のエピタキシャル成長　　　　　　　　　　　　　　　
  矢口裕之
  日本結晶成長学会誌, Volume：34, Number：4, First page：201, Last page：206, 2007
• RF-MBE growth of a-plane InN on r-plane sapphire substrates　　　　　　　　　　　　　　　
  吉田 貞史; 矢口 裕之; 折原 操
  Report of Cooperative Research Center, Saitama University, Number：8, First page：48, Last page：51, 2007
  The improvement of the surface morphology of a-plane InN films grown by RF molecular beam epitaxy is reported. Using low-temperature (LT) InN buffer layers, we could successfully obtain InN films with a smooth surface. The full width at half maximum of the x-ray diffraction (11-20) rocking curve along the [0001] InN direction was 2200 arcsec for a-plane InN samples grown at 450°C with a LT-InN buffer layer. Thus, we could improve also the crystalline quality of a-plane InN films by using LT-InN buffer layers. We observed strong polarization anisotropy in the photoluminescence spectra of a-plane InN, which is typical of nonpolar wurtzite III-nitride films.
  埼玉大学総合研究機構地域共同研究センター産学連携推進部門, Japanese
  ISSN：1347-4758, CiNii Articles ID：40016200658, CiNii Books ID：AA11808968
• Photoluminescence from Isoelectronic Traps in Dilute Nitride Semiconductor Alloys　　　　　　　　　　　　　　　
  矢口 裕之; 青木 貴嗣
  埼玉大学紀要. 工学部 第1編 第1部 論文集, Volume：39, First page：131, Last page：132, Jul. 2006
  We have studied the photoluminescence from isoelectonic traps in dilute GaAsN alloys. A number of sharp luminescence peaks due to nitrogen pairs and their phonon replicas were observed. The energy differences between the luminescence peaks and phonon replicas were 36 meV, which is in agreement with the energy of the longitudinal optical phonon at the Γ point . This indicates that the formation of isoelectronic traps is largely affected by the conduction band state at the Γ point in dilute GaAsN alloys. We have also investigated the temperature dependence of the photoluminescence related to isoelectronic traps. The energy shift of the luminescence peaks with increasing temperature is found to be almost the same as that of E0 gap of GaAs, also showing that the conduction band state at the Γ point significantly contributes to the formation of isoelectronic traps in dilute GaAsN alloys.
  埼玉大学工学部, Japanese
  ISSN：1880-4446, CiNii Articles ID：120001370441
• Towards Frontier Photonics Based on Advanced Materials　　　　　　　　　　　　　　　
  鎌田 憲彦; 明連 広昭; 矢口 裕之; 谷口 弘三
  埼玉大学紀要. 工学部 第1編 第1部 論文集, Volume：39, First page：138, Last page：142, Jul. 2006
  Based on science and technology of advanced materials, the quantum mechanical nature of photons can be utilized for expanding the available spectral window and strengthening the security of our social systems. Towards such frontier photonics, we started to study some basic elements from physical and technological aspects. We succeeded in growing β'-(BEDT-TTF)2ICl2 single crystals, detecting THz signal by our superconducting tunneling junction device. An in-situ ellipsometry enabled us to monitor thermal oxidation process of SiC surface, and a spectroscopic detection of non-radiative centers in a InAs/GaAs quantum dot structure became possible. The combination of quantum-mechanical design, nano-scale fabrication and detailed characterization is considered to be essential for proceeding the research frontier of brilliant photonics world.
  埼玉大学工学部, Japanese
  ISSN：1880-4446, CiNii Articles ID：120001370444
• RF-MBE Growth of InN/InGaN Quantum Well Structures　　　　　　　　　　　　　　　
  吉田 貞史; 矢口 裕之; 折原 操
  埼玉大学地域共同研究センター紀要, Volume：7, First page：63, Last page：63, 2006
  埼玉大学総合研究機構地域共同研究センター産学連携推進部門, Japanese
  ISSN：1347-4758, CiNii Articles ID：120001371315
• RF-MBE growth of cubic InN films on MgO (001) substrates　　　　　　　　　　　　　　　
  吉田 貞史; 矢口 裕之; 折原 操
  埼玉大学地域共同研究センター紀要, Volume：6, First page：71, Last page：71, 2005
  埼玉大学総合研究機構地域共同研究センター産学連携推進部門, Japanese
  ISSN：1347-4758, CiNii Articles ID：120001371341
• RF-MBE growth of InN epitaxial layers and InN/InGaN quantum wells on SiC substrates　　　　　　　　　　　　　　　
  吉田 貞史; 矢口 裕之; 土方 泰斗; 折原 操
  埼玉大学地域共同研究センター紀要, Volume：5, First page：63, Last page：63, 2004
  埼玉大学地域共同研究センター, Japanese
  ISSN：1347-4758, CiNii Articles ID：120001371469
• Photoemission spectroscopy and in-situ spectroscopic ellipsometry studies on the Ar post-oxidation-annealing effects of oxide/SiC interfaces　　　　　　　　　　　　　　　
  Y. Hijikata; S. Kawato; S. Sekiguchi; H. Yaguchi; Y. Ishida; M. Yoshiawa; T. Kamiya; S. Yoshida
  Proceedings of 1st Asia-Pacific Workshop on Widegap Semiconductors, First page：127, Last page：132, 2003
• Spectroscopic ellipsometry study on the dielectric functions of GaPN alloys　　　　　　　　　　　　　　　
  H Kanaya; H Yaguchi; Y Hijikata; S Yoshida; S Miyoshi; K Onabe
  5TH INTERNATIONAL CONFERENCE ON NITRIDE SEMICONDUCTORS (ICNS-5), PROCEEDINGS, Volume：0, Number：7, First page：2753, Last page：2756, 2003
  We have determined the complex dielectric functions of GaP1-xNx alloys using spectroscopic ellipsometry to clarify the electronic structure. With increasing N concentration, the E-1-gap peak height for both epsilon(1) and epsilon(2) decreases and the E-1-gap energy shifts to higher energies, showing that the electronic state at the L point is considerably changed due to the N incorporation. In the lower energy range, a broad peak appears near the fundamental band gap energy of GaP. With increasing N concentration, this peak becomes broader and the peak height increases. This indicates that the band-edge formation in GaP1-xNx alloys is extremely unique compared to that in conventional semiconductor alloys. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  WILEY-VCH, INC, English
  DOI：https://doi.org/10.1002/pssc.200303430
  DOI ID：10.1002/pssc.200303430, ISSN：1862-6351, ORCID put code：56291710, Web of Science ID：WOS:000189401700183
• Epitaxial Growth of hexagonal and cubic InN using RF-MBE　　　　　　　　　　　　　　　
  吉田 貞史; 矢口 裕之; 土方 泰斗; 折原 操
  Report of Cooperative Research Center, Saitama University, Number：4, First page：61, Last page：64, 2003
  We have grown InN films on 3C-SiC (001) substrates with and without cubic GaN underlayers by RF-MBE. It was found that, in the case of direct growth on 3C-SiC (001), hexagonal InN grows with the crystal orientation as hexagonal InN [1-100]//3C-SiC [110], while, in the case of the growth on cubic GaN underlayers, cubic InN grows with the crystal orientation as cubic InN [110]//cubic GaN [110]. Photoluminescence emissions from the cubic and hexagonal InN films were clearly observed at around 0.7 eV.
  埼玉大学地域共同研究センター, Japanese
  DOI：https://doi.org/10.24561/00016696
  DOI ID：10.24561/00016696, ISSN：1347-4758, CiNii Articles ID：120006388491, CiNii Books ID：AA11808968
• Development of Deep Ultraviolet Spectroscopic Characterization System for Nano Surface Structure of Wide Bandgap Semiconductors　　　　　　　　　　　　　　　
  矢口 裕之; 土方 泰斗
  埼玉大学地域共同研究センター紀要, Volume：3, First page：40, Last page：40, 2002
  埼玉大学地域共同研究センター, Japanese
  ISSN：1347-4758, CiNii Articles ID：120001371525
• Characterization of Oxide Films on SiC by Spectroscopic Ellipsometry　　　　　　　　　　　　　　　
  吉田 貞史; 矢口 裕之; 土方 泰斗; 折原 操
  Report of Cooperative Research Center, Saitama University, Number：3, First page：41, Last page：48, 2002
  We have developed the method of obtaining the refractive indices of SiC/oxide interfaces by use of spectroscopic ellipsometry, and by using this method we have characterized SiC/oxide interfaces obtained by various oxidation methods and/or post oxidation annealing (POA). We have designed and fabricated the system with which in situ spectroscopic ellipsometry measurements can be carried out. We have observed the initial oxidation stage of SiC. We have also observed the changes of the refractive indices of interfaces by annealing in Ar atmosphere (Ar POA). The changes of atomic bond states at the interface by Ar POA were also observed by angle-resolved XPS and UPS, and compared with the results obtained form optical measurements and C-V measurements. We have developed the measurement method of obtaining carrier density and mobility distribution in SiC wafers by use of microscopic FT-IR. We have shown that the values obtained by this method well agree with those obtained from Hall measurements, suggesting that the method is useful to characterize electrical properties of SiC wafers quantitatively, non-destructively and without contact.
  埼玉大学地域共同研究センター, Japanese
  DOI：https://doi.org/10.24561/00016656
  DOI ID：10.24561/00016656, ISSN：1347-4758, CiNii Articles ID：120006388453, CiNii Books ID：AA11808968
• Characterization of Oxide Films on SiC by Spectroscopic Ellipsometry　　　　　　　　　　　　　　　
  吉田 貞史; 矢口 裕之; 土方 泰斗; 折原 操
  Report of Cooperative Research Center, Saitama University, Number：2, First page：150, Last page：156, 2001
  The characterization of oxidized films on SiC and oxide/SiC interfaces has been carried out by use of spectroscopic ellipsometry and XPS in order to make clear their dependences on the oxidation process. It was found that the refractive indices of the interfaces depend both on the oxide formation method and the method of post oxidation annealing. We found that the refractive indices for the oxide films deposited by low temperature CVD have lower interface refractive indices than those for dry oxidation and pyrogenic oxidation, and those for post oxidation annealed in· Ar atmosphere are lower that those for quenched samples. These results correspond well with the tendencies of interface state densities obtained by electrical measurements for the samples with the corresponding oxidation processes, except the cases of the oxidation processes containing hydrogen orland hydro-oxide base, like pyrogenic oxidation and wet re-oxidation. The XPS measurements have also shown the changes in the composition and bonding nature at the interfaces by the oxidation processes. We have shown the capability of microscopic FT -IR measurements for obtaining carrier density and mobility mapping of bulk SiC wafers.
  埼玉大学地域共同研究センター, Japanese
  ISSN：1347-4758, CiNii Articles ID：40006206458, CiNii Books ID：AA11808968
• 分光偏光解析等によるSiC酸化膜の評価　　　　　　　　　　　　　　　
  吉田 貞史; 矢口 裕之; 土方 泰斗
  Number：1, First page：25, Last page：32, 2000
  Japanese
  ISSN：1347-4758, CiNii Articles ID：40006206430, CiNii Books ID：AA11808968
• Development of A New Crystal Growth Method of Silicon Carbide High-Temperature Semiconductor - Characterization of Crystal Structures andProperties　　　　　　　　　　　　　　　
  吉田 貞史; 矢口 裕之; 土方 泰斗; 折原 操
  埼玉大学地域共同研究センター紀要, Volume：1, First page：74, Last page：74, 2000
  埼玉大学地域共同研究センター, Japanese
  ISSN：1347-4758, CiNii Articles ID：120001389831
• Arsenic Surfactant and Incorporation Effects on Cubic GaN Grown by Metalorganic Vapor Phase Epitaxy
  Tokuharu KIMURA; Seikoh YOSHIDA; Jun WU; Hiroyuki YAGUCHI; Kentaro ONABE; Yasuhiro SHIRAKI
  Extended Abstracts of the 1999 International Conference on Solid State Devices and Materials, 1999, [Reviewed]
  The Japan Society of Applied Physics, English
  DOI：https://doi.org/10.7567/ssdm.1999.c-1-5
  DOI ID：10.7567/ssdm.1999.c-1-5, ORCID put code：56291742
• MOVPE Growth and Characterization of Cubic Nitrides　　　　　　　　　　　　　　　
  YAGUCHI Hiroyuki; WU Jun; ONABE Kentaro
  Technical report of IEICE. LQE, Volume：98, Number：109, First page：73, Last page：78, 16 Jun. 1998
  We have studied the growth characteristics in metalorganic vapor phase epitaxy of GaN to improve the crystal quality of cubic GaN. Photoluminescence properties of cubic nitrides of good quality have been examined in detail. In addition, we have observed stimulated emission from an optically pumped cubic GaN/AlGaN double heterostructure.
  The Institute of Electronics, Information and Communication Engineers, Japanese
  CiNii Articles ID：110003307581, CiNii Books ID：AN10442705
• Metalorganic vapor phase epitaxy of high quality cubic GaN, AlGaN and their application to optical devices
  J Wu; H Yaguchi; K Onabe; Y Shiraki
  BLUE LASER AND LIGHT EMITTING DIODES II, First page：715, Last page：718, 1998, [Reviewed]
  We report on the growth of cubic GaN and AlGaN on GaAs (100) substrates by metalorganic vapor phase epitaxy (MOVPE). High optical quality cubic nitrides were obtained by optimizing the growth conditions. X-ray diffraction measurements confirmed the highly cubic nature of these films. Photoluminescence spectra showed dominant excitonic transition for both cubic GaN and AlGaN. Strong stimulated emission was observed from the cleaved edge of optically pumped cubic GaN/AlGaN double hetero (DH) structures.
  OHMSHA LTD, English
  ORCID put code：56291604, Web of Science ID：WOS:000079631200176
• MOVPE growth of GaPAsN quaternary alloys lattice-matched to GaP　　　　　　　　　　　　　　　
  G Biwa; H Yaguchi; K Onabe; Y Shiraki
  NITRIDE SEMICONDUCTORS, Volume：482, First page：173, Last page：178, 1998, [Reviewed]
  GaP1-x-yAsyNx (x similar to 2.3%, 0 < y < 19%) quaternary alloy semiconductor films on GaP substrates have been successfully grown by metalorganic vapor phase epitaxy (MOVPE). With the fixed supplies of trimethylgallium(TMG), AsH3 and dimethylhydrazine(DMHy) during the growth, the As concentration in the solid increased with increasing AsH3 supply, while the N concentration was almost unaffected. It has been demonstrated that the crystalline quality of the alloy films is much improved with the close lattice-matching to the GaP substrate, giving a superior surface morphology without any cross-hatches, a much narrower x-ray diffraction linewidth, and a significantly higher photoluminescence(PL) intensity.
  MATERIALS RESEARCH SOCIETY, English
  ISSN：0272-9172, Web of Science ID：WOS:000073983100026
• Metalorganic Vapor Phase Epitaxy of High Quality Cubic GaN,AlGaN and Their Application to Optical Devices　　　　　　　　　　　　　　　
  J. Wu; H. Yaguchi; K. Onabe; Y. Shiraki
  Proceeding of the 2nd International Symposium on Blue Laser and Light Emitting Diodes, First page：715, Last page：718, 1998
• カソードルミネッセンスによる半導体低次元構造の評価　　　　　　　　　　　　　　　
  矢口裕之; 辻川智子; 尾鍋研太郎
  電子顕微鏡, Volume：33, First page：217, Last page：220, 1998
• High Quality Cubic GaN Growth on GaAs (100) Substrates by Metalorganic Vapor Phase Epitaxy　　　　　　　　　　　　　　　
  WU Jun; YAGUCHI Hiroyuki; ONABE Kentaro; SHIRAKI Yasuhiro; ITO Ryoichi
  Volume：1997, First page：194, Last page：195, 16 Sep. 1997
  English
  CiNii Articles ID：10017194491, CiNii Books ID：AA10777858
• Polarization Characteristics of Crescent-Shaped Tensile-Strained GaAsP/AlGaAs Quantum Wire Lasers　　　　　　　　　　　　　　　
  ISHIKAWA Mitsuteru; PAN Wugen; KANEKO Yasuhisa; YAGUCHI Hiroyuki; ONABE Kentaro; ITO Ryoichi; SHIRAKI Yasuhiro
  Volume：1997, First page：342, Last page：343, 16 Sep. 1997
  English
  CiNii Articles ID：10017194971, CiNii Books ID：AA10777858
• GaAs/AlGaAs Quantum Structures Grown in Tetrahedral-Shaped Recesses on GaAs (111)B Substrates by MOVPE　　　　　　　　　　　　　　　
  TSUJIKAWA Tomoko; MOMMA Keishi; YAGUCHI Hiroyuki; ONABE Kentaro; SHIRAKI Yasuhiro; ITO Ryoichi
  Volume：1997, First page：318, Last page：319, 16 Sep. 1997
  English
  CiNii Articles ID：10017194909, CiNii Books ID：AA10777858
• MOVPE Growth and Optical Characterization of GaPN Alloys　　　　　　　　　　　　　　　
  YAGUCHI Hiroyuki
  Technical report of IEICE. LQE, Volume：97, Number：100, First page：25, Last page：30, 17 Jun. 1997
  We have studied the growth characteristics in metalorganic vapor phase epitaxy of GaP_<1-x>N_x alloys and found that the nitrogen content in GaP_<1-x>N_x is considerably affected by the nitrogen desorption from the surface during the growth. In addition, we have clarified the radiative transition and carrier relaxation processes and the conduction band edge formation in GaP_<1-x>N_x alloys using various optical measurements.
  The Institute of Electronics, Information and Communication Engineers, Japanese
  CiNii Articles ID：110003307129, CiNii Books ID：AN10442705
• Polarization properties of GaAsP/AlGaAs tensilely strained quantum wire structures grown on V-grooved GaAs substrates
  W Pan; H Yaguchi; K Onabe; R Ito; N Usami; Y Shiraki
  COMPOUND SEMICONDUCTORS 1995, Volume：145, First page：925, Last page：930, 1996, [Reviewed]
  Crescent-shaped tensilely strained GaAs1-xPx/AlyGa1-yAs quantum wires (x = 0.11, y = 0.33) have been grown on 3-mu m-period V-grooved GaAs substrates by low-pressure metalorganic vapor phase epitaxy and characterized by cross-sectional transmission electron microscope observation, low temperature cross-sectional photoluminescence and cathodoluminescence. A drastic polarization transition from TM to TE with decreasing quantum wire size has been found in cross-sectional polarized photoluminescence.
  IOP PUBLISHING LTD, English
  ISSN：0951-3248, ORCID put code：56291587, Web of Science ID：WOS:A1996BF51P00168
• Time-resolved photoluminescence study of radiative transition processes in GaP1-xNx alloys
  H Yaguchi; S Miyoshi; H Arimoto; S Saito; H Akiyama; K Onabe; Y Shiraki; R Ito
  COMPOUND SEMICONDUCTORS 1995, Volume：145, First page：307, Last page：312, 1996, [Reviewed]
  Time-resolved photoluminescence (PL) measurements reveal that the radiative transition and carrier relaxation processes in GaP1-xNx alloys with high N concentrations are significantly different from those with low concentrations where NNi lines are clearly observed. The PL decay curve shows two distinct exponential processes for high concentrations while it is represented by a single exponential for low concentrations. The slow decay in GaP1-xNx alloys with high N concentrations indicates both the long radiative lifetime caused by the weak localization of excitons and the slow relaxation due to the scattered spatial distribution of the stales. This is consistent with the fact that the PL occurs at the tails of density of states, which is found from the comparison between absorption and PL spectra.
  IOP PUBLISHING LTD, English
  ISSN：0951-3248, ORCID put code：56291776, Web of Science ID：WOS:A1996BF51P00055
• Strain effect on direct- and indirect-gap band lineups of GaAs1-xPx/GaP quantum wells
  A Shima; H Yaguchi; K Onabe; Y Shiraki; R Ito
  COMPOUND SEMICONDUCTORS 1995, Volume：145, First page：403, Last page：408, 1996, [Reviewed]
  Strain effect on direct- and indirect-gap band lineups of strained GaAs1-xPx/GaP quantum wells with a wide range of x is studied using photoluminescence (PL) and photoreflectance (PR) spectroscopy. By comparing the transition energies obtained by PL and PR measurements with the calculation based on the effective mass approximation, it is found that the band lineups of strained GaAs1-xPx/GaP QWs on GaP substrates at any rr are of type I at the X and Gamma point and that the valence band offset of heavy hole is 506(1 - x) meV. As a result, it is deduced that biaxial compressive strain makes the energy gap of GaAs1-xPx alloys grown on GaP substrates indirect at any x.
  IOP PUBLISHING LTD, English
  ISSN：0951-3248, ORCID put code：56291588, Web of Science ID：WOS:A1996BF51P00072
• Reflectance spectroscopy of ZnCdSe/ZnSe single quantum wells　　　　　　　　　　　　　　　
  B. P. Zhang; T. Yasui; T. Yasuda; Y. Segawa; H. Yaguchi; Y. Shiraki
  Volume：11, First page：23, Last page：24, 1995
• MOVPE GROWTH OF STRAINED GAP1-XNX AND GAP1-XNX/GAP QUANTUM-WELLS
  S MIYOSHI; H YAGUCHI; K ONABE; Y SHIRAKI; R ITO
  GALLIUM ARSENIDE AND RELATED COMPOUNDS 1993, Volume：136, Number：136, First page：637, Last page：642, 1994, [Reviewed]
  We report the successful growth of GaP1-xNx (x < 0.04) alloys on GaP by metalorganic vapor phase epitaxy (MOVPE). In spite of the large miscibility gap, which is calculated to el;tend from x = 0.00001 to 0.99999 at 700 degrees C, GaP1-xNx alloys have been obtained at the growth temperature of 630 similar to 700 degrees C. The peak energy of low-temperature photoluminescence (PL) spectra shows a redshift with increasing x. We have made strained GaP1-xNx (well) / GaP (barrier) multiple quantum wells (MQWs) and observed strong PL emission from these MQWs.
  IOP PUBLISHING LTD, English
  ISSN：0951-3248, ORCID put code：56291580, Web of Science ID：WOS:A1994BB30L00105
• DETERMINATION OF BAND OFFSETS IN GAASP/GAP STRAINED-LAYER QUANTUM-WELL STRUCTURES USING PHOTOREFLECTANCE AND PHOTOLUMINESCENCE SPECTROSCOPY
  Y HARA; H YAGUCHI; K ONABE; Y SHIRAKI; R ITO
  GALLIUM ARSENIDE AND RELATED COMPOUNDS 1993, Volume：136, Number：136, First page：361, Last page：366, 1994, [Reviewed]
  GaAs1-xPx(x=0.81,0.84,0.86) /GaP strained-layer quantum well (SLQW) structures have been studied using photoreflectance(PR) as well as photoluminescence(PL) spectroscopy. The PR measurements have revealed the optical transitions between the quantized subbands in the higher-lying quantum well at the Gamma point. From the PR measurements, combined with a square-potential effective-mass calculation, the conduction band offset ratio has been determined to be 0.68+/-0.1 for x=0.84. This result leads to the type-I quantum well at the X-point conduction band minima. The low-temperature PL spectra are very consistent with the type-I band scheme.
  IOP PUBLISHING LTD, English
  ISSN：0951-3248, ORCID put code：56291623, Web of Science ID：WOS:A1994BB30L00060
• Initial Oxidation of MBE-Grown Si Surfaces　　　　　　　　　　　　　　　
  T. Igarashi; H. Yaguchi; K. Fujita; S. Fukatsu; Y. Shiraki; R. Ito; T. Hattori
  MRS Proceedings, Volume：220, First page：35, Last page：39, 1991, [Reviewed]
  We investigated the initial oxidation of MBE-grown Si (100) surfaces with atomic flatness using x-ray photoemission spectroscopy (XPS) and reflection high energy electron diffraction (RHEED). It was found that the MBE-grown surfaces are inert and hardly oxidized even after exposure to molecular oxygen up to 1500 Langmuir (L) at room temperature. At elevated temperatures, the surface oxidation was substantially promoted. On the contrary, the surface oxidation was found to be substantiated on a deliberately corrugated Si surface prepared by low temperature MBE growth, even at room temperature.
  Springer Science and Business Media LLC, English
  DOI：https://doi.org/10.1557/proc-220-35
  DOI ID：10.1557/proc-220-35, ISSN：0272-9172, eISSN：1946-4274, ORCID put code：56291586, Web of Science ID：WOS:A1991BU84B00005
• Suppression of Interfacial Mixing by Sb Deposition in Si/Ge Strained-Layer Superlattices　　　　　　　　　　　　　　　
  K. Fujita; S. Fukatsu; H. Yaguchi; T. Igarashi; Y. Shiraki; R. Ito
  MRS Proceedings, Volume：220, First page：193, Last page：197, 1991, [Reviewed]
  We have studied interfacial mixing of Si/Ge strained-layer superlattices during Si molecular beam epitaxy. The mixing has been shown to be primarily due to the surface segregation of Ge atoms during Si overlayer growth. It has been found that only the Ge atoms on the topmost Ge layer dominantly segregate to the growing surface. It has also been found that the surface segregation of Ge is effectively suppressed by depositing Sb atoms on the Ge layers. It has been demonstrated that Si/Ge superlattices with abrupt Si/Ge interfaces can be grown by depositing Sb. The two state exchange model is used to discuss the surface segregation of Ge and the suppression of the segregation by Sb deposition.
  Springer Science and Business Media LLC, English
  DOI：https://doi.org/10.1557/proc-220-193
  DOI ID：10.1557/proc-220-193, ISSN：0272-9172, eISSN：1946-4274, ORCID put code：56291656, Web of Science ID：WOS:A1991BU84B00029
• KINETICS OF GE SEGREGATION IN THE PRESENCE OF SB DURING MOLECULAR-BEAM EPITAXY　　　　　　　　　　　　　　　
  S FUKATSU; K FUJITA; H YAGUCHI; Y SHIRAKI; R ITO
  SILICON MOLECULAR BEAM EPITAXY, Volume：220, First page：217, Last page：222, 1991, [Reviewed]
  MATERIALS RESEARCH SOC, English
  DOI：https://doi.org/10.1557/PROC-220-217
  DOI ID：10.1557/PROC-220-217, ORCID put code：56291583, Web of Science ID：WOS:A1991BU84B00033
• Initial oxidation of MBE-grown Si surfaces
  T. Igarashi; H. Yaguchi; K. Fujita; S. Fukatsu; Y. Shiraki; R. Ito; T. Hattori
  Silicon Molecular Beam Epitaxy Symposium, Volume：651, First page：35, Last page：39, 1991
  We investigated the initial oxidation of MBE-grown Si (100) surfaces with atomic flatness using x-ray photoemission spectroscopy (XPS) and reflection high energy electron diffraction (RHEED). It was found that the MBE-grown surfaces are inert and hardly oxidized even after exposure to molecular oxygen up to 1500 Langmuir (L) at room temperature. At elevated temperatures, the surface oxidation was substantially promoted. On the contrary, the surface oxidation was found to be substantiated on a deliberately corrugated Si surface prepared by low temperature MBE growth, even at room temperature.
  Springer Science and Business Media LLC
  DOI：https://doi.org/10.1557/proc-220-35
  DOI ID：10.1557/proc-220-35, ISSN：0272-9172, eISSN：1946-4274
• Suppression of interfacial mixing by Sb deposition in Si/Ge strained-layer superlattices
  K. Fujita; S. Fukatsu; H. Yaguchi; T. Igarashi; Y. Shiraki; R. Ito
  Silicon Molecular Beam Epitaxy Symposium, Volume：651, First page：193, Last page：197, 1991
  We have studied interfacial mixing of Si/Ge strained-layer superlattices during Si molecular beam epitaxy. The mixing has been shown to be primarily due to the surface segregation of Ge atoms during Si overlayer growth. It has been found that only the Ge atoms on the topmost Ge layer dominantly segregate to the growing surface. It has also been found that the surface segregation of Ge is effectively suppressed by depositing Sb atoms on the Ge layers. It has been demonstrated that Si/Ge superlattices with abrupt Si/Ge interfaces can be grown by depositing Sb. The two state exchange model is used to discuss the surface segregation of Ge and the suppression of the segregation by Sb deposition.
  Springer Science and Business Media LLC
  DOI：https://doi.org/10.1557/proc-220-193
  DOI ID：10.1557/proc-220-193, ISSN：0272-9172, eISSN：1946-4274
• Kinetics of Ge segregation in the presence of Sb during molecular beam epitaxy　　　　　　　　　　　　　　　
  S. Fukatsu; K. Fujita; H. Yaguchi; Y. Shiraki; R. Ito
  Silicon Molecular Beam Epitaxy Symposium, Volume：651, First page：217, Last page：222, 1991
• 28p-K-10 Glide Velocity of Dislocations in Heteroepitaxial Thin Films　　　　　　　　　　　　　　　
  Yamashita Y.; Maeda K.; Mera Y.; Yaguchi H.; Shiraki Y.
  Meeting Abstracts of the Physical Society of Japan, Volume：46, Number：0, First page：41, Last page：41, 1991
  The Physical Society of Japan, Japanese
  DOI ID：10.11316/jpsgaiyod.46.2.0_41_2, CiNii Articles ID：110002149886, CiNii Books ID：AN10453938