Faculty Profiles - HONDA, Yoshio

Papers - HONDA, Yoshio

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Visualization of Different Carrier Concentrations in n-Type GaN Semiconductors by Phase-Shifting Electron Holography with Multiple Electron Biprisms Reviewed

Kazuo Yamamoto, Kiyotaka Nakano, Atsushi Tanaka, Yoshio Honda, Yuto Ando, Masaya Ogura, Miko Matsumoto, Satoshi Anada, Yukari Ishikawa, Hiroshi Amano, Tsukasa Hirayama

Microscopy Vol. 69 ( 1 ) page： 1 - 10 2020.2

Scalable synthesis of multilayer h-BN on AlN by metalorganic vapor phase epitaxy: nucleation and growth mechanism Reviewed

Yang Xu, Nitta Shugo, Pristovsek Markus, Liu Yuhuai, Liao Yaqiang, Kushimoto Maki, Honda Yoshio, Amano Hiroshi

2D MATERIALS Vol. 7 ( 1 ) 2020.1

Language：English Publishing type：Research paper (scientific journal) Publisher：IOP PUBLISHING LTD

We studied the nucleation and growth of hexagonal BN (h-BN) on AlN template on c-plane sapphire by metalorganic vapor phase epitaxy as functions of growth temperature, deposition time, and triethylboron (TEB) partial pressure. A lateral growth rate of about 25 nm min(-1) for h-BN nuclei was obtained by atomic force microscopy and a nucleation activation energy of 2.1 eV was extracted from the temperature dependence of the nucleation density. A large TEB flow rate strongly enhances the formation of h-BN nuclei. At a reduced TEB flow rate, we observed a significantly decreased nuclei density and a delay in nucleation due to TEB desorption. By fine tuning the growth parameters, single-crystalline multilayer h-BN was successfully formed on AlN surface, as confirmed by x-ray diffraction and transmission electron microscopy (TEM). The epitaxial relationship between h-BN and AlN was [0 0 0 1](h-BN) parallel to [0 0 0 1](AlN) and [1 0 -10](h-BN) parallel to [1 1 -20](AlN) from TEM and electron backscatter diffraction measurements. In addition, TEM showed that the initial h-BN layers are not parallel and tend to form half-domes. On those half-domes (cap-shaped-like) a 2D lateral growth sets on, resulting in a well-oriented 2D multilayer observed in TEM. Thus, the surface topography further develops to form a relatively flat surface without wrinkles and finally a typical hexagon-like wrinkled surface at thicker h-BN layers. Particularly, the small h-BN nuclei have dangling bonds at their periphery that can interact with the substrate, forming actual bonds with AlN. Hence the choice on the substrate is important, despite the basal planes of multilayer h-BN are bonded by a weak van der Waals force.

DOI： 10.1088/2053-1583/ab46e6

Web of Science

Recovery of quantum efficiency on Cs/O-activated GaN and GaAs photocathodes by thermal annealing in vacuum

Daiki Sato, Tomohiro Nishitani, Yoshio Honda, Hiroshi Amano

JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B Vol. 38 ( 1 ) 2020.1

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

In this paper, the authors describe the effectiveness of thermal annealing in vacuum for quantum efficiency (QE) recovery from Cs/O-activated GaN and GaAs photocathodes. The QE of Cs/O-activated GaN photocathodes at 3.4eV dropped from 1.0% to <0.001% upon exposure to nitrogen and then increased to 0.6% upon annealing. On the other hand, the QE of Cs/O-activated GaAs at 1.42eV did not increase after annealing. In addition, after Cs/O activation, the sample was exposed to normal laboratory air and installed in an X-ray photoemission spectroscopy system. Upon annealing at 330<degrees>C, three key results were confirmed as follows: (1) the work function decreased by 0.32eV, (2) the chemical states of Cs 4d and Ga 3d were unchanged, and (3) the intensities of O 1s and C 1s on the high-binding-energy side decreased. In conclusion, the experimental results indicate that the annealing recovers the QE of Cs/O-activated GaN photocathode.

DOI： 10.1116/1.5120417

Web of Science

Characterization of AlGaN multiple-quantum-wells grown on <i>c</i>-plane AlN/sapphire templates with macro-steps

Kojima Kazunobu, Nagasawa Yosuke, Hirano Akira, Ippommatsu Masamichi, Sugie Ryuichi, Honda Yoshio, Amano Hiroshi, Akasaki Isamu, Chichibu Shigefusa F.

Journal of the Japanese Association for Crystal Growth Vol. 47 ( 3 ) page： n/a 2020

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japanese Association for Crystal Growth

<p> The microscopic structural and optical characteristics of AlGaN light-emitting diodes (LEDs) fabricated on the AlN templates with dense macrosteps are shown to clarify the origin of their high internal quantum efficiency of radiation (IQE). The cross-sectional transmission electron microscopy observations under the high-angle annular dark field scanning mode and microscopic energy dispersive X-ray spectroscopy revealed that the AlGaN cladding layer under the AlGaN quantum well (QW) layer had a microscopic compositional modulation, which originates from the macrosteps at the AlN template surface. Moreover, Ga-rich portions in the cladding layer behaved as current micropaths, and the micropaths are connected with the carrier localization structure formed in QWs. The in-plane cathodoluminescence (CL) spectroscopy showed a significant inhomogeneity of the CL characteristics. The gentle slopes at the sample surface showed brighter emissions with a lower peak photon energy, confirming the carrier localization. This carrier localization structure in the QWs combined with the current micropaths in the cladding layer can increase the IQE as well as external quantum efficiency of the AlGaN LEDs.</p>

DOI： 10.19009/jjacg.47-3-04

CiNii Research

Dielectric Ruduced Surface Field Effect on Vertical GaN-on-GaN Nanowire Schottky Barrier Diodes

Yaqiang Liao, Tao Chen, Jia Wang, Yuto Ando, Xu Yang, Hirotaka Watanabe, Jun Hirotani, Maki Kushimoto, Manato Deki, Atsushi Tanaka, Shugo Nitta, Yoshio Honda, Kevin J. Chen, Hiroshi Amano

Proceedings of the International Symposium on Power Semiconductor Devices and ICs Vol. 2020-September page： 349 - 352 2020

Language：English Publishing type：Research paper (international conference proceedings)

In this work, gallium nitride (GaN) nanowire (NW) Schottky barrier diodes was fabricated using well-optimized top-down approach. As-fabricated $100 \times 800$-nm-diameter NWs SBD with high current density over 1kA/cm2 at a forward bias of 2.2V, a low differential specific ON-resistance of $0.15\mathrm{m} \Omega \cdot cm^{2}$ are demonstrated. By the virtue of dielectric Reduced Surface Field (RESURF) effect, the device also delivers a breakdown voltage of 515V, leading to a competitive Baliga's Figure of merit of 1.76 GW/cm2.

DOI： 10.1109/ispsd46842.2020.9170101

Web of Science

Scopus

Untwinned semipolar (10(1)over-bar3) AlxGa1-xN layers grown on m-plane sapphire Reviewed

Dinh Duc V, Hu Nan, Amano Hiroshi, Honda Yoshio, Pristovsek Markus

SEMICONDUCTOR SCIENCE AND TECHNOLOGY Vol. 34 ( 12 ) 2019.12

Suppression of Green Luminescence of Mg-Ion-Implanted GaN by Subsequent Implantation of Fluorine Ions at High Temperature Reviewed

M. Takahashi, A. Tanaka, Y. Ando, H. Watanabe, M. Deki, M. Kushimoto, S. Nitta, Y. Honda, K. Shima, K. Kojima, S. F. Chichibu, K. J. Chen, H. Amano

Physica Status Solidi (b) Vol. 257 page： 1900554 - 1900554 2019.12

Two-dimensional analysis of the nonuniform quantum yields of multiple quantum wells for AlGaN-based deep-ultraviolet LEDs grown on AlN templates with dense macro-steps using cathodoluminescence spectroscopy Reviewed

Y. Nagasawa, R. Sugie, K. Kojima, A. Hirano, M. Ipponmatsu, Y. Honda, H. Amano, I. Akasaki, S. F. Chichibu

Journal of Applied Physics Vol. 126 ( 21 ) page： 215703 1 - 10 2019.12

Low Voltage High-Energy α-Particle Detectors by GaN-on-GaN Schottky Diodes with Record-High Charge Collection Efficiency. Reviewed

Sandupatla A, Arulkumaran S, Ranjan K, Ng GI, Murmu PP, Kennedy J, Nitta S, Honda Y, Deki M, Amano H

Sensors (Basel, Switzerland) Vol. 19 ( 23 ) 2019.11

Aluminium incorporation in polar, semi- and non-polar AlGaN layers: a comparative study of x-ray diffraction and optical properties Reviewed

Duc V Dinh, Hu Nan, Honda Yoshio, Amano Hiroshi, Pristovsek Markus

SCIENTIFIC REPORTS Vol. 9 ( 1 ) page： 15802 2019.11

V-shaped dislocations in a GaN epitaxial layer on GaN substrate Reviewed

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

AIP ADVANCES Vol. 9 ( 9 ) 2019.9

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

In this study, V-shaped dislocations in a GaN epitaxial layer on a free-standing GaN substrate were observed. Our investigation further revealed that the V-shaped dislocations were newly generated at the interface in the epilayer rather than propagated from the GaN substrate. V-shaped dislocations consist of two straight parts. The straight parts of the V-shaped dislocations were separated from each other in the m-direction and tilted toward the step-flow direction of the GaN epitaxial layer. The V-shaped dislocations are continuous single dislocations having a Burgers vector component of 1a and an intrinsic stacking fault between their straight parts.

DOI： 10.1063/1.5114866

Web of Science

Scopus

Precise Measurement of Carrier Concentrations in n-Type GaN by Phase-Shifting Electron Holography

Kazuo Yamamoto, Kiyotaka Nakano, Atsushi Tanaka, Yoshio Honda, Yuto Ando, Masaya Ogura, Miko Matsumoto, Satoshi Anada, Yukari Ishikawa, Hiroshi Amano, Tsukasa Hirayama

Microscopy and Microanalysis Vol. 25 ( S2 ) page： 50 - 51 2019.8

Origin of acceptor diffusion into silicon substrate during GaN growth by metal organic chemical vapor deposition Reviewed

Matsumoto Koji, Ono Toshiaki, Honda Yoshio, Torigoe Kazuhisa, Kushimoto Maki, Amano Hiroshi

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 58 ( 7 ) 2019.7

Ammonia decomposition and reaction by high-resolution mass spectrometry for group III - Nitride epitaxial growth Reviewed

Ye Zheng, Nitta Shugo, Nagamatsu Kentaro, Fujimoto Naoki, Kushimoto Maki, Deki Manato, Tanaka Atsushi, Honda Yoshio, Pristovsek Markus, Amano Hiroshi

JOURNAL OF CRYSTAL GROWTH Vol. 516 page： 63 - 66 2019.6

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

The decomposition of ammonia (NH3) in nitrogen (N-2) ambient was studied under non-equilibrium conditions similar to those in a metal organic vapor phase epitaxy (MOVPE) reactor during the epitaxial growth of group-III nitrides. The gas phase was sampled at different positions and analyzed using a time-of-flight mass spectrometry system with a high resolution (better than 0.002 u). Our results expand earlier findings. Even at the high temperature of 1200 degrees C, only 26% of NH3 decomposed in a clean metal-free reactor, whereas a higher ratio of NH3 decomposition was realized in the presence of stainless steel. The activation energy in the clean reactor was calculated to be 0.965 +/- 0.004 eV. These results demonstrate the capability of our setup and shed new light on the elucidation of the vapor phase growth mechanism of group III-nitrides by MOVPE.

DOI： 10.1016/j.jcrysgro.2019.03.025

Web of Science

Direct evidence of Mg diffusion through threading mixed dislocations in GaN p-n diodes and its effect on reverse leakage current Reviewed International journal

Shigeyoshi Usami, Norihito Mayama, Kazuya Toda, Atsushi Tanaka, Manato Deki, Shugo Nitta, Yoshio Honda, Hiroshi Amano

APPLIED PHYSICS LETTERS Vol. 114 ( 23 ) 2019.6

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

Mg diffusion is a common problem in GaN devices with p-n junctions. Although this impurity diffusion is reported to occur through threading dislocations (TDs), no direct evidence has yet been obtained. Therefore, we tried the direct observation of Mg diffusion by atom probe tomography (APT) analysis. The n-type drift layer of the fabricated p-n diode was exposed, and etch pits were formed on the drift layer to identify the TD position. The APT analysis around TDs was carried out by lifting out the drift layer around specific etch pits using a focused ion beam to include TDs. The relationship between the etch pit shape and the TD type was confirmed by cross-sectional scanning transmission electron microscopy observation. The APT analysis of two types of etch pits formed on the mixed dislocations was performed, and Mg diffusion was clearly observed through the mixed dislocations. In this work, we show direct evidence of Mg diffusion via mixed dislocations in GaN p-n diodes and its effect on reverse leakage current.

DOI： 10.1063/1.5097767

Web of Science

Computational fluid dynamics simulation study of the gas flow balance in a vertical HVPE reactor with a showerhead for low cost bulk GaN crystal growth Reviewed

Liu Qiang, Fujimoto Naoki, Nitta Shugo, Honda Yoshio, Amano Hiroshi

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 58 2019.6

Frontiers of Nitride Semiconductor Research FOREWORD Reviewed

Chichibu Shigefusa F, Kumagai Yoshinao, Kojima Kazunobu, Deura Momoko, Akiyama Toru, Arita Munetaka, Fujioka Hiroshi, Fujiwara Yasufumi, Hara Naoki, Hashizume Tamotsu, Hirayama Hideki, Holmes Mark, Honda Yoshio, Imura Masataka, Ishii Ryota, Ishitani Yoshihiro, Iwaya Motoaki, Kamiyama Satoshi, Kangawa Yoshihiro, Katayama Ryuji, Kawakami Yoichi, Kawamura Takahiro, Kobayashi Atsushi, Kuzuhara Masaaki, Matsumoto Koh, Mori Yusuke, Mukai Takashi, Murakami Hisashi, Murotani Hideaki, Nakazawa Satoshi

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 58 2019.6

Effect of photoelectrochemical etching and post-metallization annealing on gate controllability of AlGaN/GaN high electron mobility transistors Reviewed International journal

Keisuke Uemura, Manato Deki, Yoshio Honda, Hiroshi Amano, Taketomo Sato

Japanese Journal of Applied Physics Vol. 58 ( SC ) page： SCCD20-1 - SCCD20-6 2019.6

Deeply and vertically etched butte structure of vertical GaN p-n diode with avalanche capability Reviewed International journal

Hayata Fukushima, Shigeyoshi Usami, Masaya Ogura, Yuto Ando, Atsushi Tanaka, Manato Deki, Maki Kushimoto, Shugo Nitta, Yoshio Honda, Hiroshi Amano

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 58 2019.6

Language：English Publishing type：Research paper (scientific journal) Publisher：IOP PUBLISHING LTD

A vertical p-n diode with a simple edge termination structure on a GaN free-standing substrate is demonstrated. The edge of this device is terminated simply by etching a drift layer deeply and vertically. A device simulation revealed that the electric field at the device edge was more relaxed and uniformly applied by etching the mesa deeper than the depletion region. The fabricated device showed low leakage current and avalanche capability, and its breakdown characteristics could be reproduced many times. By emission microscopy observation, we found that there was no leakage current at the side wall of the device and that avalanche breakdown occurred throughout the inside of the device. This indicates that the electric field crowding at the side wall of the device was completely suppressed and a uniform electric field distribution was obtained by this structure. (C) 2019 The Japan Society of Applied Physics

DOI： 10.7567/1347-4065/ab106c

Web of Science

Correlation between nanopipes formed from screw dislocations during homoepitaxial growth by metal-organic vapor-phase epitaxy and reverse leakage current in vertical p-n diodes on a free-standing GaN substrates Reviewed International journal

Shigeyoshi Usami, Atsushi Tanaka, Hayata Fukushima, Yuto Ando, Manato Deki, Shugo Nitta, Yoshio Honda, Hiroshi Amano

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 58 2019.6

Language：English Publishing type：Research paper (scientific journal) Publisher：IOP PUBLISHING LTD

We fabricated p-n diodes under different growth pressures on free-standing GaN substrates of the same quality and observed a noteworthy difference in the reverse leakage current. A large reverse leakage current was generated by nanopipes, which were formed from screw dislocations in the homoepitaxial layer. There were two types of screw dislocation observed in this study. The first type already existed in the substrate and the other was newly generated in the epilayer by the coalescence of edge and mixed dislocations. An increase in the growth pressure suppressed the transformation of screw dislocations into nanopipes, which led to a reduction in the reverse leakage current. To reduce the leakage current further, it is necessary to apply growth conditions that do not transform screw dislocation into nanopipes and to use a free-standing substrate without threading dislocations, that become nanopipes. (C) 2019 The Japan Society of Applied Physics

DOI： 10.7567/1347-4065/ab1250

Web of Science

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Papers - HONDA, Yoshio