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Papers by Author: Isamu Akasaki

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Growth and Light Properties of Fluorescent SiC for White LEDs

Authors: Mikael Syväjärvi, Rositza Yakimova, Motoaki Iwaya, Tetsuya Takeuchi, Isamu Akasaki, Satoshi Kamiyama

Abstract: The LED technology started to developed many years ago with red light emitting diodes. To achieve the blue LED, novel growth technologies and process steps were explored, and made it possible to demonstrate efficient blue LED performance from nitrides. The efficiency was further developed and blue LEDs were commercially introduced in the 1990’s. The white LED became possible by the use of the blue LED and a phosphor that converts a part of the blue light to other colors in the visible range to combine into white light. However, even today there are limitations in the phosphor-based white LED technology, in particular for general lighting, and new solutions should be explored to speed the pace when white LEDs will be able to make substantial energy savings. In this paper we overview gallium nitride materials evolution and growth concepts for LEDs. We describe the fluorescent silicon carbide material prepared by a novel growth technology for a new type of white LED in general lighting with pure white light. This paper introduces an interesting research in fundamental growth and optical properties of light emitting silicon carbide.

AlN and AlGaN by MOVPE for UV Light Emitting Devices

Authors: Hiroshi Amano, Masataka Imura, Motoaki Iwaya, Satoshi Kamiyama, Isamu Akasaki

Abstract: The fundamental growth issues of AlN and AlGaN on sapphire and SiC using metalorganic vapor phase epitaxy, particularly the growth of AlN and AlGaN on a groove-patterned template are reviewed. In addition, the conductivity control of AlGaN is shown. The conductivity control of p-type AlGaN, particularly the realization of a high hole concentration, is essential for realizing high-efficiency UV and DUV LEDs and LDs.

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Dependence of DAP Emission Properties on Impurity Concentrations in N-/B-co-doped 6H-SiC

Authors: Satoshi Murata, Yoshihiro Nakamura, Tomohiko Maeda, Yoko Shibata, Mina Ikuta, Masaaki Sugiura, Shugo Nitta, Motoaki Iwaya, Satoshi Kamiyama, Hiroshi Amano, Isamu Akasaki, Masahiro Yoshimoto, Tomoaki Furusho, Hiroyuki Kinoshita

Abstract: The dependence of donor-acceptor pair (DAP) emission properties on impurity concentrations of N and B in 6H-SiC epilayers was investigated. Doped samples were grown by closed sublimation technique, and impurity concentrations were confirmed by secondary ion mass spectrometry (SIMS). Photoluminescence (PL) measurement results indicate that p-type 6H-SiC with NA>ND had extremely low DAP emission efficiency, whereas n-type 6H-SiC with NA

335

6H-SiC Homoepitaxial Growth and Optical Property of Boron- and Nitrogen-Doped Donor-Acceptor Pair (DAP) Emission of 1º-Off Substrate by Closed-Space Sublimation Method

Authors: Y. Kawai, Tomohiko Maeda, Yoshihiro Nakamura, Yoji Sakurai, Motoaki Iwaya, Satoshi Kamiyama, Hiroshi Amano, Isamu Akasaki, Masahiro Yoshimoto, Tomoaki Furusho, Hiroyuki Kinoshita, Hiromu Shiomi

Abstract: We demonstrate high-speed and high-quality 6H-SiC homoepitaxial growth on a 1°-off c-plane SiC substrate by a closed-space sublimation method. By optimizing the size of single-crystal source materials in the growth system, a high-quality 6H-SiC epilayer with an X-ray diffraction rocking curve (0006) full-width at the half maximum (FWHM) of 38 arcsec was obtained. We also carried out doping of nitrogen and boron during the growth of the SiC epilayer. A strong donor-acceptor pair (DAP) emission at a peak wavelength of 570 nm under excitation by a 395 nm nitride-based light-emitting diode (LED) was observed. The 6H-SiC with DAP emission is promising for use as a phosphor in a nitride-based LED, because high-quality nitride layers can be grown on the SiC substrates with small off-oriented angles.

263

Photoluminescence and Electroluminescence Characterization of In_xGa_1-xN/In_yGa_1-yN Multiple Quantum Well Light Emitting Diodes

Authors: Peder Bergman, G.R. Pozina, Bo Monemar, Satoshi Kamiyama, Motoaki Iwaya, Hiroshi Amano, Isamu Akasaki

1493

Luminescence of InGaN/GaN Multiple Quantum Wells Grown by Mass-Transport

Authors: G.R. Pozina, Peder Bergman, Bo Monemar, Motoaki Iwaya, Shoji Nitta, Hiroshi Amano, Isamu Akasaki

791

Radiative Recombination in InGaN/GaN Multiple Quantum Wells

Authors: Peder Bergman, Bo Monemar, G.R. Pozina, B.E. Sernelius, P.O. Holtz, Hiroshi Amano, Isamu Akasaki

1571

Room Temperature Photoluminescence Linewidth versus Material Quality of GaN

Authors: Bo Monemar, I.A. Buyanova, Peder Bergman, Hiroshi Amano, Isamu Akasaki

1319

Heteroepitaxy of Group III Nitrides for Device Applications

Authors: Hiroshi Amano, T. Takeuchi, Hiroshi Sakai, S. Yamaguchi, C. Wetzel, Isamu Akasaki

1115

Charactrization of Residual Transition Metal Ions in GaN and AIN

Authors: J. Baur, Ulrich Kaufmann, M. Kunzer, J. Schneider, Hiroshi Amano, Isamu Akasaki, T. Detchprohm, K. Hiramatsu