Faculty Profiles - HONDA, Yoshio

Papers - HONDA, Yoshio

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m-Plane GaN Schottky Barrier Diodes Fabricated With MOVPE Layer on Several Off-Angle m-Plane GaN Substrates Open Access

Atsushi Tanaka, Yuto Ando, Kentaro Nagamatsu, Manato Deki, Heajeong Cheong, Barry Ousmane, Maki Kushimoto, Shugo Nitta, Yoshio Honda, Hiroshi Amano

Physica Status Solidi (A) Applications and Materials Science Vol. 215 ( 9 ) 2018.5

Language：English Publishing type：Research paper (scientific journal) Publisher：Wiley-VCH Verlag

In this study, GaN m-plane Schottky barrier diodes are fabricated by metalorganic vapor-phase epitaxy (MOVPE) on several off-angle gallium nitride (GaN) substrates, and the off-cut angle dependence of impurity incorporation is investigated. We show that the MOVPE layer on the substrate inclined 5° toward the [000–1] direction has extremely low impurity incorporation. These results provide important suggestions for the fabrication of m-plane power devices.

DOI： 10.1002/pssa.201700645

Interface amorphization in hexagonal boron nitride films on sapphire substrate grown by metalorganic vapor phase epitaxy Reviewed Open Access

Vol. 11 ( 5 ) 2018.5

Reduction of Dislocations in GaN on Silicon Substrate Using In Situ Etching Open Access

Koji Matsumoto, Toshiaki Ono, Yoshio Honda, Tetsuya Yamamoto, Shigeyoshi Usami, Maki Kushimoto, Satoshi Murakami, Hiroshi Amano

PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS Vol. 255 ( 5 ) 2018.5

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

A gallium nitride (GaN) epitaxial layer with a low density of threading dislocations is successfully grown on a silicon substrate by using in situ gas etching. Silicon nitride (SiNx) film is used as a mask, and ammonia is intermittently supplied in hydrogen ambient during the etching. After etching, high-density deep pits appeared on the surface of a GaN template layer and corresponded to the threading dislocations in the layer. In this novel method, before growing an additional GaN layer on the template GaN layer, a second SiNx layer is deposited after the etching process, and this layer prevents GaN nuclei from growing on the upper side-walls of the pits. By using this method, the density of threading dislocations of the GaN surface is reduced to 6.7x10(7)cm(-2). This method is cost effective, completing all the necessary processes in one growth run without taking samples out from a metalorganic chemical vapor deposition (MOCVD) reactor.

DOI： 10.1002/pssb.201700387

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 ) 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

Growth of hexagonal boron nitride on sapphire substrate by pulsed-mode metalorganic vapor phase epitaxy International journal 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 page： 1 - 8 2018.1

Language：English 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

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

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

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

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

Charge-to-time converting leading-edge discriminator for plastic-scintillator signals International journal

T. Ishikawa, Y. Takeda, Y. Honda, Y. Inoue, H. Kanda, S. Kido, Y. Matsumura, M. Miyabe, I. Nagasawa, H. Shimizu, T. Takeda, A. O. Tokiyasu, Y. Tsuchikawa, H. Yamazaki

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT Vol. 875 page： 193 - 200 2017.12

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

We have developed a charge-to-time converting (QTC) leading-edge discriminator for plastic-scintillator signals, which is packaged in a NIM-standard double-width module. The pulse width of the discriminator output is approximately proportional to the charge integration of input signals up to 40-50 pC. The non-linearity is 20%, 10%, 4%, and 2% at maximum for the input charges below 7 pC, for 7-10 pC, for 10-20 pC, and above 20 pC, respectively, for the minimum input charges larger than 2 pC. The discriminator could be suitable in the measurement of the timing and charge of plastic-scintillator signals together with a multi-hit time-to-digital converter (TDC) module. (C) 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.nima.2017.09.040

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

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

APPLIED PHYSICS LETTERS Vol. 111 ( 12 ) 2017.9

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

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 International journal

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

APPLIED PHYSICS EXPRESS Vol. 10 ( 8 ) 2017.8

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

The internal electric fields in III-polar (0001), N-polar (0001), and semipolar (1011) InGaN/GaN light-emitting diodes were investigated by electroreflectance (ER) spectroscopy. The ER spectra reflected the difference in the direction and strength of internal electric fields. Phase analyses of the ER signal revealed that only III-polar InGaN wells have the opposite direction of the internal electric field at zero bias voltage; this finding is in good agreement with the results of numerical analyses. Quantitative analyses of internal electric fields were conducted by the linewidth analyses of ER spectra. Our experimental results indicate that the absolute value of internal electric fields can be measured from ER spectra. (C) 2017 The Japan Society of Applied Physics

DOI： 10.7567/APEX.10.082101

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

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

PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS Vol. 254 ( 8 ) 2017.8

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

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. (C) 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

DOI： 10.1002/pssb.201600722

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

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

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

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

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 International journal

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

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

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

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

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

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

PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS Vol. 254 ( 8 ) 2017.8

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

In this study, by using time-of-flight (TOF) high-resolution and high-sensitivity mass spectrometry measurements, the decomposition of trimethylgallium into dimethylgallium and monomethylgallium along with its adduct formation with NHx in a commercially available horizontal metalorganic vapor-phase epitaxy (MOVPE) reactor with a resistive heater was investigated and observed in more detail than previously reported. The results confirmed the use of the TOF monitoring system in analyzing the elementary reaction process in actual MOVPE systems. (C) 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

DOI： 10.1002/pssb.201600737

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

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

JOURNAL OF CRYSTAL GROWTH Vol. 468 page： 866 - 869 2017.6

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

A-plane GaN was attempted to be grown on (11-20) 4H-SiC bulk substrate without using a traditional thick buffer layer. By inducing TMAl treatment before the GaN growth step and using both a low pressure and V/III ratio, the interlayer thickness of the a-plane GaN/SiC was reduced to 1.7 +/- 0.5 nm. The ultrathin interlayer was observed to be either AlN or AlGaN with a low Ga composition. This study is aimed to contribute to the understanding of GaN growth on the sidewalls of c-plane trench structure SiC. The ultrathin growth technique is also hoped to be applied to the fabrication of GaN-based vertical structure nonpolar optical or electrical devices.

DOI： 10.1016/j.jcrysgro.2017.01.031

Orientation-controlled epitaxial lateral overgrowth of semipolar GaN on Si(001) with a directionally sputtered AlN buffer layer International journal

Ho-Jun Lee, Si-Young Bae, Kaddour Lekhal, Akira Tamura, Takafumi Suzuki, Maki Kushimoto, Yoshio Honda, Hiroshi Amano

JOURNAL OF CRYSTAL GROWTH Vol. 468 page： 547 - 551 2017.6

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

We successfully grew semipolar (10 (1) over bar3) and (10 (1) over bar5) GaN films on Si(001) substrates employing metal-organic chemical vapor deposition (MOCVD) by inserting a directionally sputtered AlN (DS-AlN) buffer layer. To improve the crystal quality of the orientation-controlled semipolar (10 (1) over bar3) and (10 (1) over bar5) GaN films, a two-step epitaxial lateral overgrowth (ELO) process was performed with a striped mask. According to low-temperature cathodoluminescence (LT-CL) characterization, the ELO results in a coalesced morphology and a low defect density of < 2.72x10(8) cm(-2) for both semipolar (10<(1)over bar>3) and (10 (1) over bar5) GaN films. For comparing the properties of planar and ELO semipolar GaN, a rocking curve of x-ray diffraction (XRD) and low-temperature photoluminescence (LT-PL) spectra was measured. The crystal orientation of semipolar GaN films was confirmed using electron backscatter diffraction (EBSD).

DOI： 10.1016/j.jcrysgro.2016.11.116

Effect of V/III ratio on the surface morphology and electrical properties of m-plane (10(1)over-bar0) GaN homoepitaxial layers International journal

Ousmane I. Barry, Atsushi Tanaka, Kentaro Nagamatsu, Si-Young Bae, Kaddour Lekhal, Junya Matsushita, Manato Deki, Shugo Nitta, Yoshio Honda, Hiroshi Amano

JOURNAL OF CRYSTAL GROWTH Vol. 468 page： 552 - 556 2017.6

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

We have investigated the effect of V/III ratio on the surface morphology, impurity concentration and electrical properties of m-plane (10 (1) over bar0) Gallium Nitride (GaN) homoepitaxial layers. Four-sided pyramidal hillocks are observed on the nominally on-axis m-plane GaN films. Hillocks sizes relatively increase by increasing the V/III ratio. All facets of pyramidal hillocks exhibit well-defined step-terrace features. Secondary ion mass spectrometry depth profiles reveal that carbon impurities decrease by increasing the V/III ratio while the lowest oxygen content is found at an optimized V/III ratio of 900. Vertical Schottky barrier diodes fabricated on the m-GaN samples were characterized. Low leakage current densities of the order of 10(-10) A/cm(2) at -5 V are obtained at the optimum V/III ratio. Oxygen impurities and screw-component dislocations around hillocks are found to have more detrimental impact on the leakage current mechanism.

DOI： 10.1016/j.jcrysgro.2016.12.012

Uneven AlGaN multiple quantum well for deep-ultraviolet LEDs grown on macrosteps and impact on electroluminescence spectral output Reviewed

Vol. 56 ( 6 ) 2017.6

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

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

JOURNAL OF CRYSTAL GROWTH Vol. 468 page： 110 - 113 2017.6

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

Severe melt-back etching has forced the epitaxy of GaN on Si to use an AlN buffer layer for growing high-quality two-dimensional layers, despite its high resistivity. Herein, we report a metal-based pre-orienting layer (POL) for growing GaN nanostructures (NSs) to replace the traditional AlN buffer layer. Two metals, titanium (Ti) and hafnium (Hf), were evaluated as POLs. We succeeded in fabricating arrays of GaN NSs with highly preferred orientation using selective-area growth. The crystallographic phase of the POLs critically affected the evolved orientation of the crystals. Photoluminescence measurements revealed that GaN NSs with Hf-based POLs were of reasonably high quality. We believe that this result will facilitate broader III-V semiconductor applications using alternative substrates moving beyond conventional Si-based optoelectronics.

DOI： 10.1016/j.jcrysgro.2016.10.032

Annealing effect on threading dislocations in a GaN grown on Si substrate International journal

H. Iwata, H. Kobayashi, T. Kamiya, R. Kamei, H. Saka, N. Sawaki, M. Irie, Y. Honda, H. Amano

JOURNAL OF CRYSTAL GROWTH Vol. 468 page： 835 - 838 2017.6

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

Effect of rapid thermal annealing (RTA) on crystal defects in a GaN layer grown on a (111) Si substrate was investigated by photoluminescence (PL) and transmission electron microscopy (TEM) analyses. The PL spectra suggested that the density of gallium vacancy is not changed by the heat treatment up to 700 degrees C. In the TEM specimen, we had dislocation half loops generated by off-axis propagation of the threading dislocation. We found that the half-loop of c-type dislocation shrinks/moves by a repetitive RTA at 600-700 degrees C. In contrast, we could find no remarkable changes in the a-type or a+c-type dislocations.

DOI： 10.1016/j.jcrysgro.2017.01.001

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