Yoshinao Kumagai

Tokyo University of Agriculture and Technology

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Hisashi Murakami

Tokyo University of Agriculture and Technology

176

Akinori Koukitu

Tokyo University of Agriculture and Technology

169

Ken Goto

Tokyo University of Agriculture and Technology

Rie Togashi

Sophia University

Masataka Higashiwaki

National Institute of Information and Communications Technology

Akito Kuramata

Crystal Research (United States)

Bo Monemar

Lund University

Shigenobu Yamakoshi

Tokyo University of Agriculture and Technology

Toru Nagashima

Tokuyama (Japan)

Keita Konishi

Crystal Research (United States)

Cooperative Institutions

Tokyo University of Agriculture and Technology

136

Tohoku University

Osaka University

The University of Tokyo

University of Tsukuba

Nagoya University

Tokyo Institute of Technology

Kyoto University

National Institute of Information and Communications Technology

North Carolina State University

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Vacancy compensation and related donor-acceptor pair recombination in bulk AlN

Applied Physics Letters (2013)

Benjamin E. Gaddy Zachary Bryan Isaac Bryan Ronny Kirste Jinqiao Xie

A prominent 2.8 eV emission peak is identified in bulk AlN substrates grown by physical vapor transport. This peak is shown to be related to the carbon concentration in the samples. Density functional theory calculations predict that this emission is caused by a donor-acceptor pair (DAP) recombination between substitutional carbon on the nitrogen site and a nitrogen vacancy. Photoluminescence and photoluminescence-excitation spectroscopy are used to confirm the model and indicate the DAP character of the emission. The interaction between defects provides a pathway to creating ultraviolet-transparent AlN substrates for optoelectronics applications.

Acceptor

Carbon fibers

Wide-bandgap semiconductor

Ultraviolet

10.1063/1.4824731

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Citations (88)

Introduction of Singular Structure of Group-III Nitrides by HVPE Using a Mixed System of III-Cl and III-Cl 3

The Japan Society of Applied Physics (2015)

Yoshinao Kumagai

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Thermodynamic analysis of β-Ga₂O₃ growth by molecular beam epitaxy

Japanese Journal of Applied Physics (2022)

Rie Togashi Haruka Ishida Ken Goto Masataka Higashiwaki Yoshinao Kumagai

Abstract Thermodynamic analyses of β -Ga 2 O 3 growth by both ozone and plasma-assisted molecular beam epitaxy (MBE) were performed. In either case, the growth mechanism was found to differ depending on whether the input VI/III ratio was above or below 1.5. Under O-rich conditions (VI/III > 1.5), the driving force for β -Ga 2 O 3 growth ( Δ P Ga 2 O 3 ) was determined to increase linearly with increasing Ga input partial pressure ( P Ga o ) because almost all the supplied Ga was used for the growth of the β -Ga 2 O 3 . In contrast, Ga-rich conditions (VI/III < 1.5) caused Δ P Ga 2 O 3 to decrease. Etching of the β -Ga 2 O 3 occurred with increasing P Ga o due to the formation of volatile Ga 2 O. This work also demonstrated that the use of ozone allowed growth at higher temperatures than the use of O radicals. The calculated results were in good agreement with experimental values, indicating that β -Ga 2 O 3 growth by MBE can be explained by thermodynamics.

10.35848/1347-4065/ac9bb2

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Citations (4)

Two-Step Growth of (0001) ZnO Single-Crystal Layers on (0001) Sapphire Substrates by Halide Vapor Phase Epitaxy

Japanese Journal of Applied Physics (2011)

Rui Masuda Rie Togashi Hisashi Murakami Yoshinao Kumagai Akinori Koukitu

The heteroepitaxial growth of (0001) ZnO on (0001) sapphire substrates by halide vapor phase epitaxy using a two-step growth procedure was investigated. X-ray diffraction analysis revealed that single-crystal (0001) ZnO layers on (0001) sapphire substrates were grown at 400 °C. High-temperature heteroepitaxy at 1000 °C on (0001) sapphire substrates was realized by two-step growth using the ZnO layer grown at 400 °C as a buffer layer. Two-dimensional layer growth at 1000 °C was realized on buffer layers thicker than 0.4 µm. Photoluminescence (PL) measurements performed at room temperature for the ZnO layer grown on the 0.4-µm-thick buffer layer showed a significant blueshift of near-band-edge emission (NBE). A thick buffer layer of 0.8 µm was found to be necessary for a successful two-step growth without a blueshift of NBE in the PL spectra, which is caused by a large compressive stress.

Blueshift

Crystal (programming language)

10.7567/jjap.50.125503

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High-speed epitaxial growth of AlN above by hydride vapor phase epitaxy

Journal of Crystal Growth (2007)

Toru Nagashima Manabu Harada Hiroyuki Yanagi Yoshinao Kumagai Akinori Koukitu

Susceptor

Atmospheric temperature range

Vapor phase

10.1016/j.jcrysgro.2006.10.260

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Citations (39)

Impact of crystallization manner of the buffer layer on the crystalline quality of GaN epitaxial layers on GaAs (1 1 1)A substrate

Journal of Crystal Growth (2004)

Hisashi Murakami Nobuhiko Kawaguchi Yoshihiro Kangawa Yoshinao Kumagai Akinori Koukitu

Buffer (optical fiber)

10.1016/j.jcrysgro.2004.11.197

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Citations (5)

Formation of periodic step and terrace structure on Si(100) surface during annealing in hydrogen diluted with inert gas

Journal of Vacuum Science & Technology A Vacuum Surfaces and Films (1998)

Yoshinao Kumagai Keiichi Namba Tadahiro Komeda Yasushiro Nishioka

Annealing of a Czochralski Si(100) substrate in a gas flow in which H2 is diluted to a concentration of 3% in He was investigated. The surfaces annealed at 900 °C or above showed well-developed terraces with mono-atomic steps that alternate between the straight A-step and the zigzag B-step configurations, whereas no morphological improvement occurred in the surfaces annealed at temperatures below 900 °C, as confirmed by atomic force microscopy. Reflection high-energy electron diffraction observations and Fourier-transform infrared attenuated total reflection spectra of the flat surfaces clarified that the surface Si atoms make dimers with their dangling bonds terminated by H atoms, i.e., the surface reconstruction is Si(100)2×1/1×2-H. We show that the depth of the etching was not sufficient to account for the observed smoothening of the surface during the annealing at high temperatures, and conclude that the main mechanism of surface flattening is surface migration of the Si atoms.

Flattening

Dangling bond

Surface reconstruction

Inert gas

10.1116/1.581301

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Citations (31)

Transmission Electron Microscope Analysis of Microstructures in GaN Grown on (111)A and (111)B of GaAs by Metalorganic Hydrogen Chloride Vapor-Phase Epitaxy

physica status solidi (a) (2001)

T. Mitate Yoshiko Sonoda K. Oki N. Kuwano Yoshinao Kumagai

Cross-sectional transmission electron microscope (TEM) observation has been performed for GaN grown simultaneously on (111)A and (111)B of a GaAs substrate by metalorganic hydrogen chloride vapor-phase epitaxy. A low-temperature (LT) buffer layer of GaN about 85 nm thick was deposited at 550°C, and then a thick layer of GaN (HT-GaN) was grown at 920°C. On GaAs(111)A, the LT-buffer layer has a fine columnar structure and its stacking order is of 2H (wurtzite) or a mixture of 2H and 3C (zincblende). On the LT-layer, the HT-GaN was grown in the wurtzite structure with Ga-polarity. In the HT-GaN, a columnar structure is formed on the interface of GaN/LT-GaN, and a good quality GaN is grown in the upper region. These characteristics in microstructure are very similar to those in GaN grown on α-Al 2 O 3 by the conventional two-step growth method. On GaAs(111)B, the LT-buffer layer has a disordered stacking sequence. A block structure is formed on the interface of GaN/LT-GaN, and the HT-GaN has a fairly good quality. The HT-GaN has Ga-polarity in spite of the fact that the substrate has As-polarity.

Wurtzite crystal structure

10.1002/1521-396x(200112)188:2<557::aid-pssa557>3.0.co;2-

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Preface

Journal of Crystal Growth (2011)

Jaime A. Freitas Zlatko Sitar Yoshinao Kumagai Elke Meissener

Poisson's equation

10.1016/j.jcrysgro.2011.12.011

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Preparation of Large Freestanding GaN Substrates by Hydride Vapor Phase Epitaxy Using GaAs as a Starting Substrate : Semiconductors