Faculty Profiles - AMANO, Hiroshi

Papers - AMANO, Hiroshi

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Correlation between dislocations and leakage current of p-n diodes on a free-standing GaN substrate

Shigeyoshi Usami, Yuto Ando, Atsushi Tanaka, Kentaro Nagamatsu, Manato Deki, Maki Kushimoto, Shugo Nitta, Yoshio Honda, Hiroshi Amano, Yoshihiro Sugawara, Yong-Zhao Yao, Yukari Ishikawa

APPLIED PHYSICS LETTERS Vol. 112 ( 18 ) page： 182106 2018.4

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER INST PHYSICS

Dislocations that cause a reverse leakage current in vertical p-n diodes on a GaN free-standing substrate were investigated. Under a high reverse bias, dot-like leakage spots were observed using an emission microscope. Subsequent cathodoluminescence (CL) observations revealed that the leakage spots coincided with part of the CL dark spots, indicating that some types of dislocation cause reverse leakage. When etch pits were formed on the dislocations by KOH etching, three sizes of etch pits were obtained (large, medium, and small). Among these etch pits, only the medium pits coincided with leakage spots. Additionally, transmission electron microscopy observations revealed that pure screw dislocations are present under the leakage spots. The results revealed that lc pure screw dislocations are related to the reverse leakage in vertical p-n diodes. Published by AIP Publishing.

DOI： 10.1063/1.5024704

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Light output performance of red AlGaInP-based light emitting diodes with different chip geometries and structures Open Access

Oh Jeong-Tak, Lee Sang-Youl, Moon Yong-Tae, Moon Ji Hyung, Park Sunwoo, Hong Ki Yong, Song Ki Young, Oh Chan-Hyoung, Shim Jong-In, Jeong Hwan-Hee, Song June-O, Amano Hiroshi, Seong Tae-Yeon

OPTICS EXPRESS Vol. 26 ( 9 ) page： 11194-11200 2018.4

The 2018 GaN power electronics roadmap Open Access

H. Amano, Y. Baines, E. Beam, Matteo Borga, T. Bouchet, Paul R Chalker, M. Charles, Kevin J Chen, Nadim Chowdhury, Rongming Chu, Carlo De Santi, Maria Merlyne De Souza, Stefaan Decoutere, L. Di Cioccio, Bernd Eckardt, Takashi Egawa, P. Fay, Joseph J Freedsman, L. Guido, Oliver Häberlen, Geoff Haynes, Thomas Heckel, Dilini Hemakumara, Peter Houston, Jie Hu, Mengyuan Hua, Qingyun Huang, Alex Huang, Sheng Jiang, H. Kawai, Dan Kinzer, Martin Kuball, Ashwani Kumar, Kean Boon Lee, Xu Li, Denis Marcon, Martin März, R. McCarthy, Gaudenzio Meneghesso, Matteo Meneghini, E. Morvan, A. Nakajima, E. M.S. Narayanan, Stephen Oliver, Tomás Palacios, Daniel Piedra, M. Plissonnier, R. Reddy, Min Sun, Iain Thayne, A. Torres, Nicola Trivellin, V. Unni, Michael J Uren, Marleen Van Hove, David J Wallis, J. Wang, J. Xie, S. Yagi, Shu Yang, C. Youtsey, Ruiyang Yu, Enrico Zanoni, Stefan Zeltner, Yuhao Zhang

Journal of Physics D: Applied Physics Vol. 51 ( 16 ) page： 163001 2018.4

Language：English Publishing type：Research paper (scientific journal) Publisher：Institute of Physics Publishing

Gallium nitride (GaN) is a compound semiconductor that has tremendous potential to facilitate economic growth in a semiconductor industry that is silicon-based and currently faced with diminishing returns of performance versus cost of investment. At a material level, its high electric field strength and electron mobility have already shown tremendous potential for high frequency communications and photonic applications. Advances in growth on commercially viable large area substrates are now at the point where power conversion applications of GaN are at the cusp of commercialisation. The future for building on the work described here in ways driven by specific challenges emerging from entirely new markets and applications is very exciting. This collection of GaN technology developments is therefore not itself a road map but a valuable collection of global state-of-the-art GaN research that will inform the next phase of the technology as market driven requirements evolve. First generation production devices are igniting large new markets and applications that can only be achieved using the advantages of higher speed, low specific resistivity and low saturation switching transistors. Major investments are being made by industrial companies in a wide variety of markets exploring the use of the technology in new circuit topologies, packaging solutions and system architectures that are required to achieve and optimise the system advantages offered by GaN transistors. It is this momentum that will drive priorities for the next stages of device research gathered here.

DOI： 10.1088/1361-6463/aaaf9d

Analysis of Cesium Layer on InGaN by Temperature Programmed Desorption Method

Kashima Masahiro, Daiki Sato, Atsushi Koizumi, Tomohiro Nishitani, Yoshio Honda, Hiroshi Amano, Hokuto Iijima, Takashi Meguro

JSAP Annual Meetings Extended Abstracts Vol. 2018.1 ( 0 ) page： 1670 - 1670 2018.3

Chronicity of Anterior Cruciate Ligament Deficiency, Part 1: Effects on the Tibiofemoral Relationship Before and Immediately After Anatomic ACL Reconstruction With Autologous Hamstring Grafts Open Access

Tanaka, Y; Kita, K; Takao, R; Amano, H; Uchida, R; Shiozaki, Y; Yonetani, Y; Kinugasa, K; Mae, T; Horibe, S

ORTHOPAEDIC JOURNAL OF SPORTS MEDICINE Vol. 6 ( 1 ) 2018.1

Growth of hexagonal boron nitride on sapphire substrate by pulsed-mode metalorganic vapor phase epitaxy Open Access

Xu Yang, Shugo Nitta, Kentaro Nagamatsu, Si-Young Bae, Ho-Jun Lee, Yuhuai Liu, Markus Pristovsek, Yoshio Honda, Hiroshi Amano

JOURNAL OF CRYSTAL GROWTH Vol. 482 ( 15 ) page： 1 - 8 2018.1

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Hexagonal boron nitride (h-BN) was directly grown on sapphire substrate using alternating ammonia (NH3) and triethylboron (TEB) supply (pulsed mode) in metalorganic vapor phase epitaxy. The best condition is when just enough NH3 is supplied to fully convert the TEB within one cycle. Excess NH3 caused islands on h-BN film surface while a lack of NH3 does not form h-BN at all. The epitaxial relationship between grown h-BN layer and c-plane sapphire was confirmed to be [0001](h-BN)||[0001](sapphire) and [10-10](h-BN)||[11-20](sapphire). It is known that, compared to AlN, BN requires higher V/III ratios for good crystallinity, which due to severe gas-phase reactions is difficult to achieve using continuous supply. Thus using pulsed mode the FWHM of the symmetric (0002) diffraction was almost halved and the growth rate was several times faster. (C) 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jcrysgro.2017.10.036

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Electrical and Thermal Analysis of Vertical GaN-on-GaN PN Diodes

Yates Luke, Pavlidis Georges, Graham Samuel, Usami Shigeyoshi, Nagamatsu Kentaro, Honda Yoshio, Amano Hiroshi

PROCEEDINGS OF THE 17TH IEEE INTERSOCIETY CONFERENCE ON THERMAL AND THERMOMECHANICAL PHENOMENA IN ELECTRONIC SYSTEMS (ITHERM 2018) page： 831 - 837 2018

Theoretical Study of the Electronic Structure of Threading Edge Dislocations in GaN

Nakano Takashi, Araidai Masaaki, Shiraishi Kenji, Tanaka Atsushi, Honda Yoshio, Amano Hiroshi

GALLIUM NITRIDE AND SILICON CARBIDE POWER TECHNOLOGIES 8 Vol. 86 ( 12 ) page： 41 - 49 2018

DFT modeling of carbon incorporation in GaN(0001) and GaN(000(1)over-bar) metalorganic vapor phase epitaxy Reviewed

Pawel Kempisty, Yoshihiro Kangawa, Akira Kusaba, Kenji Shiraishi, Stanislaw Krukowski, Michal Bockowski, Koichi Kakimoto, and Hiroshi Amano

APPLIED PHYSICS LETTERS Vol. 111 page： 141602/1-5 2017.10

Language：English Publishing type：Research paper (scientific journal)

The carbon incorporation mechanism in GaN(0001) and GaN(000 (1) over bar) during MOVPE was investigated using density functional theory (DFT) calculations. The results confirm that the crucial factors for carbon incorporation are Fermi level pinning and accompanying surface band bending. In addition, the lattice symmetry has a strong dependence on the stability of carbon in a few subsurface layers, which results from interactions between the impurities and surface states. It was shown that these effects are responsible for facilitating or hindering the incorporation of impurities and dopants. The influence of diluent gas species (hydrogen or nitrogen) on carbon incorporation was discussed.

DOI： 10.1063/1.4991608

Initial leakage current paths in the vertical-type GaN-on-GaN Schottky barrier diodes

Liwen Sang, Bing Ren, Masatomo Sumiya, Meiyong Liao, Yasuo Koide, Atsushi Tanaka, Yujin Cho, Yoshitomo Harada, Toshihide Nabatame, Takashi Sekiguchi, Shigeyoshi Usami, Yoshio Honda, and Hiroshi Amano

APPLIED PHYSICS LETTERS Vol. 111 page： 122102/1-5 2017.9

Language：English Publishing type：Research paper (scientific journal)

Electrical characteristics of leakage current paths in vertical-type n-GaN Schottky barrier diodes (SBDs) on free-standing GaN substrates are investigated by using photon emission microscopy (PEM). The PEM mapping shows that the initial failure of the SBD devices at low voltages is due to the leakage current paths from polygonal pits in the GaN epilayers. It is observed that these polygonal pits originate from carbon impurity accumulation to the dislocations with a screw-type component by microstructure analysis. For the SBD without polygonal pits, no initial failure is observed and the first leakage appeals at the edge of electrodes as a result of electric field concentration. The mechanism of leakage at pits is explained in terms of trap assisted tunneling through fitting current-voltage characteristics.

DOI： 10.1063/1.4994627

Absolute technique for measuring internal electric fields in InGaN/GaN light-emitting diodes by electroreflectance applicable to all crystal orientations Reviewed

Tomoyuki Tanikawa, Kanako Shojiki, Ryuji Katayama, Shigeyuki Kuboya, Takashi Matsuoka, Yoshio Honda, and Hiroshi Amano

Applied Physics Express Vol. 10 page： 082101/1-4 2017.8

Low cost high voltage GaN polarization superjunction field effect transistors Open Access

H. Kawai, S. Yagi, S. Hirata, F. Nakamura, T. Saito, Y. Kamiyama, M. Yamamoto, H. Amano, V. Unni, E. M. S. Narayanan

PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE Vol. 214 ( 8 ) page： 1600834/1-10 2017.8

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

A comprehensive overview of the novel high voltage GaN field effect transistors (FETs) based on the Polarization Superjunction (PSJ) concept, and a cost-effective approach towards manufacturing these high performance devices are presented. Current challenges impeding wider adoption of GaN power switching transistors in applications, and the latest results of the scaled-up PSJ-FETs from POWDEC KK, are also discussed. The article also presents hard-switching characteristics of 400-800V boost converter, constructed using a PSJ-FET grown on sapphire substrate, and the future direction of GaN power semiconductor technology based on monolithic integration for advanced power electronics.

DOI： 10.1002/pssa.201600834

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Facet dependence of leakage current and carrier concentration in m-plane GaN Schottky barrier diode fabricated with MOVPE Reviewed

Atsushi Tanaka, Ousmane1 Barry, Kentaro Nagamatsu, Junya Matsushita, Manato Deki, Yuto Ando, Maki Kushimoto, Shugo Nitta, Yoshio Honda, and Hiroshi Amano

Phys. Status Solidi A Vol. 214 ( 8 ) page： 1600829/1-5 2017.8

Language：English Publishing type：Research paper (scientific journal)

In this study, GaN m-plane Schottky barrier diodes fabricated with a metalorganic vapor-phase epitaxy on a GaN substrate were investigated using emission microscope, photoluminescence, and cathodoluminescence. In addition, facet dependence of leakage current under reverse-biased condition was observed. We showed that the leakage-current distribution was caused by the facet dependence of the carrier concentration and oxygen concentration. These results can provide important suggestions for the fabrication of m-plane devices. (a) four-faceted hillocks on m-plane GaN MOVPE sample, facet dependence of (b) leakage current and (c) PL peak intensity of the m-plane GaN Schottky barrier diode.

DOI： 10.1002/pssa.201600829

Effect of dislocations on the growth of p-type GaN and on the characteristics of p-n diodes Invited Reviewed

Shigeyoshi Usami, Ryosuke Miyagoshi, Atsushi Tanaka, Kentaro Nagamatsu, Maki Kushimoto, Manato Deki, Shugo Nitta, Yoshio Honda, and Hiroshi Amano

Phys. Status Solidi A Vol. 214 ( 8 ) page： 1600837/1-5 2017.8

Language：English Publishing type：Research paper (scientific journal)

We investigate the influence of crystal defects on p-type GaN grown by metalorganic vapor phase epitaxy. Sets of p-type GaN films were grown on sapphire substrates and on free-standing GaN (F-GaN) substrates simultaneously using various Et-Cp2Mg flow rates. Although there is a difference of two orders of magnitude between the threading dislocation densities of p-type GaN grown on sapphire and F-GaN substrates, there is no significant difference in hole concentration. However, there are problems with the surface morphology of p-type GaN grown on sapphire. The deterioration of the surface was caused by the difference in nanopipe density. The electrical properties of a p-n junction diode formed on sapphire with a high density of nanopipes were observed using emission microscopy under both forward- and reverse-bias conditions. Our results demonstrate that the nanopipes are electrically inactive, and that other types of threading dislocation have more influence on the current-voltage characteristics.

DOI： 10.1002/pssb.201600722

Selective-area growth of doped GaN nanorods by pulsed-mode MOCVD: Effect of Si and Mg dopants Reviewed

Si-Young Bae, Kaddour Lekhal, Ho-Jun Lee, Jung-Wook Min, Dong-Seon Lee, Yoshio Honda, and Hiroshi Amano

Phys. Status Solidi B Vol. 254 ( 8 ) page： 1600722/1-7 2017.8

Language：English Publishing type：Research paper (scientific journal)

Injecting current with a uniform carrier concentration is important for applications with three-dimensional architectures such as vertical power devices or displays. In III-nitride nanostructures, dopants not only incorporate differently depending on the surface orientation but can also seriously affect the kinetic equilibrium shapes of the nanorods. Herein, we report selective-area growth of doped GaN nanorods grown by pulsed-mode metalorganic chemical vapor deposition. Two dopants, Si and Mg, were employed as donor and acceptor atoms, respectively, for a mono-doping approach. Furthermore, a mixed flow of Si and Mg was supplied for a co-doping approach. We compared the morphological effects and growth rates of each doped GaN nanorod array. Then, we proposed appropriate growth mechanisms for the doped GaN nanorods on the basis of our structural characterizations. These results might extend the morphological functionality of GaN nanorods by including doping and may also provide an appropriate foundation for the design of nanostructure-based electronic or photonic devices.

DOI： 10.1002/pssb.201600722

Decomposition of trimethylgallium and adduct formation in a metalorganic vapor phase epitaxy reactor analyzed by high-resolution gas monitoring system Reviewed

Kentaro Nagamatsu, Shugo Nitta, Zheng Ye, Hirofumi Nagao, Shinichi Miki, Yoshio Honda, and Hiroshi Amano

Phys. Status Solidi B Vol. 254 ( 8 ) page： 1600737/1-4 2017.8

Effect of dislocations on the growth of p-type GaN and on the characteristics of p-n diodes

Usami Shigeyoshi, Miyagoshi Ryosuke, Tanaka Atsushi, Nagamatsu Kentaro, Kushimoto Maki, Deki Manato, Nitta Shugo, Honda Yoshio, Amano Hiroshi

PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE Vol. 214 ( 8 ) 2017.8

Language：English Publishing type：Research paper (scientific journal) Publisher：Physica Status Solidi (A) Applications and Materials Science

We investigate the influence of crystal defects on p-type GaN grown by metalorganic vapor phase epitaxy. Sets of p-type GaN films were grown on sapphire substrates and on free-standing GaN (F-GaN) substrates simultaneously using various Et-Cp2Mg flow rates. Although there is a difference of two orders of magnitude between the threading dislocation densities of p-type GaN grown on sapphire and F-GaN substrates, there is no significant difference in hole concentration. However, there are problems with the surface morphology of p-type GaN grown on sapphire. The deterioration of the surface was caused by the difference in nanopipe density. The electrical properties of a p–n junction diode formed on sapphire with a high density of nanopipes were observed using emission microscopy under both forward- and reverse-bias conditions. Our results demonstrate that the nanopipes are electrically inactive, and that other types of threading dislocation have more influence on the current–voltage characteristics.

DOI： 10.1002/pssa.201600837

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Role of threading dislocations in strain relaxation during GaInN growth monitored by real-time X-ray reflectivity Reviewed

Guangxu Ju, Masao Tabuchi, Yoshikazu Takeda, and Hiroshi Amano

Applied Physics Letters Vol. 110 ( 26 ) page： 262105/1-5 2017.6

A-plane GaN growth on (11-20) 4H-SiC substrate with an ultrathin interlayer Reviewed

Zheng Sun, Peifeng Song, Shugo Nitta, Yoshio Honda, Hiroshi Amano

Journal of Crystal Growth Vol. 468 page： 866-869 2017.6

Selective-area growth of vertically oriented GaN nanostructures with a hafnium pre-orienting layer Reviewed

S.-Y.Bae, K. Lekhal, H.-J.Lee, T.Mitsunari, J.-W.Min, D.-S.Leed, M.Kushimoto, Y.Honda, H.Amano

Journal of Crystal Growth Vol. 468 page： 110-113 2017.6

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Papers - AMANO, Hiroshi