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Asubar, Joel T. Zenji Yatabe Gregusova, Dagmar Hashizume, Tamotsu
Published in
Journal of Applied Physics
Gallium nitride (GaN) is one of the front-runner materials among the so-called wide bandgap semiconductors that can provide devices having high breakdown voltages and are capable of performing efficiently even at high temperatures. The wide bandgap, however, naturally leads to a high density of surface states on bare GaN-based devices or interface ...
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Low, Rui Shan Asubar, Joel T. Baratov, Ali Kamiya, Shunsuke Nagase, Itsuki Urano, Shun Kawabata, Shinsaku Tokuda, Hirokuni Kuzuhara, Masaaki Nakamura, Yusui
...
Published in
Applied Physics Express
We report on the fabrication and characterization of AlGaN/GaN metal-insulator-semiconductor (MIS) capacitors and high-electron-mobility transistors (MIS-HEMTs) using a 5 nm thick Al2O3 dielectric deposited by cost-effective and environmental-friendly mist chemical vapor deposition (mist-CVD) technique. Practically hysteresis-free capacitance–volta...
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Hidema, Ruri Zenji Yatabe Takahashi, Hikari Higashikawa, Ryusei Suzuki, Hiroshi
Published in
Soft Matter
Complex fluids have a non-uniform local inner structure; this is enhanced under deformation, inducing a characteristic flow, such as an abrupt increase in extensional viscosity and drag reduction. However, it is challenging to derive and quantify the non-uniform local structure of a low-concentration solution. In this study, we attempted to charact...
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Zenji Yatabe NISHIYAMA, Koshi TSUDA, Takaaki NAKAMURA, Yusui
Published in
Journal of the Ceramic Society of Japan
Excellent quality amorphous aluminum oxide (AlOx) thin films have been obtained by atmospheric pressure solution-processed mist chemical vapor deposition (mist-CVD) technique at 400°C using water-free solvent. X-ray fluorescence investigations verified the formation of AlOx film by the mist-CVD. X-ray diffraction, X-ray photoelectron spectroscopy, ...
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Escaño, Mary Clare S. Asubar, Joel T. Zenji Yatabe David, Melanie Y. Uenuma, Mutsunori Tokuda, Hirokuni Uraoka, Yukiharu Kuzuhara, Masaaki Tani, Masahiko
Published in
Applied Surface Science
We conducted X-ray photoelectron spectroscopy (XPS) and first-principles calculations based on density functional theory (DFT) to confirm the presence of Ga2O sub-oxide in high-pressure water vapor annealed AlGaN surface. We note that the Ga 3d XPS peak broadens and shifts towards higher binding energies, which suggests surface oxide formation. Dec...
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Zenji Yatabe Nishiyama, Koshi Tsuda, Takaaki Nakamura, Yusui Nishimura, Kazuki
Published in
Japanese Journal of Applied Physics
Aluminum titanium oxide (Al1–x Ti x O y , an alloy of Al2O3 and TiO2), an attractive high-κ dielectric material, was synthesized by mist chemical vapor deposition, utilizing Al2O3 and TiO2 precursors. X-ray diffraction investigations revealed that the Al1–x Ti x O y (0
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Zenji Yatabe Nishiyama, Koshi Tsuda, Takaaki Nishimura, Kazuki Nakamura, Yusui
Published in
2019 Compound Semiconductor Week (CSW)
With its wide-bandgap (~7 eV), high breakdown field (~10 MV/cm) and high dielectric constant (~9) amorphous aluminum oxide (Al 2 O 3 ) film is an attractive material for applications as gate insulator and/or surface passivation layers for electrical devices. Using several vacuum deposition techniques, such as sputtering, metal organic chemical vapo...
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Win, Thant Zin Furukawa, Takumi Tanaka, Yudai Okita, Koshi Sue, Koji Zenji Yatabe Nakamura, Yusui
Published in
2019 Compound Semiconductor Week (CSW)
Tin oxide (SnO 2 ) is an n-type wide band-gap semiconductor with excellent properties such as optical, electrical and chemical properties. In this research, SnO 2 thin films were grown on m-plane sapphire substrates by mist chemical vapor deposition. However, it was difficult to deposit high quality SnO 2 films because of the large lattice mismatch...
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Zenji Yatabe Nishiyama, Koshi Tsuda, Takaaki Nishimura, Kazuki Nakamura, Yusui
Published in
2019 Compound Semiconductor Week (CSW)
High-k dielectric aluminum titanium oxide (AlTiO, an alloy of Al 2 O 3 and TiO 2 ) films were obtained by mist chemical vapor deposition (mist-CVD), utilizing Al 2 O 3 and TiO 2 precursors. By X-ray fluorescence (XRF) investigations, atomic composition ratios of Al and Ti ratios in the Al x Ti y O films were verified. X-ray diffraction (XRD) reveal...
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Asubar, Joel Tokuda, Hirokuni Kuzuhara, Masaaki Zenji Yatabe Nishiguchi, Kenya Hashizume, Tamotsu
Published in
PISIKA - Journal of the Physics Society of the Philippines
With its wide bandgap of 3.4 eV, gallium nitride (GaN) is considered as a key semiconductor material for realizing ultra-low-loss power devices. However, GaN-based devices is still plagued by current collapse, which is the temporary reduction of current after application of electrical stress. In this work, we present the state-of-art Multi-Mesa-Cha...
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Okita, Koshi Inaba, Katsuhiko Zenji Yatabe Nakamura, Yusui
Published in
Japanese Journal of Applied Physics
ZnS is attractive as a material for low-cost light-emitting diodes. In this study, a non-polar ZnS layer was epitaxially grown on a sapphire substrate by inserting a ZnO buffer layer between ZnS and sapphire. The ZnS and ZnO layers were grown by a mist chemical vapor deposition system with a simple setup operated under atmospheric pressure. The sam...
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Hashizume, Tamotsu Nishiguchi, Kenya Kaneki, Shota Kuzmik, Jan Zenji Yatabe
Published in
Materials Science in Semiconductor Processing
In this article, we review recent progress on AlGaN/GaN and InAlN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) using Al-based oxides, nitride dielectrics, SiO2 and high-k dielectrics. Although GaN MIS-HEMTs have been suffering from the instability of threshold voltage (VTH), recent interface technologies using in...
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Zenji Yatabe Inoue, Shinya Asubar, Joel T. Kasai, Seiya
Published in
Applied Physics Express
An analytical technique is proposed to reveal the relaxation time distribution of dynamic charge events using the current noise spectrum of a transistor, by applying an inverse integral transformation to the McWhorter model. In the proposed method, the continuous relaxation-time distribution function G(τ) can be analytically derived from the noise ...
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Okita, K. Goto, T. Tanaka, Y. Takenouchi, M. Yatabe, Z. Nakamura, Y. Zenji Yatabe
Published in
Extended Abstracts of the 2017 International Conference on Solid State Devices and Materials
Non-polar ZnS layers were epitaxially grown on mplane sapphire substrates by mist chemical vapor deposition at atmospheric pressure. For this growth, ZnO buffer layers were inserted between the ZnS and the sapphire because ZnO has an intermediate lattice constant.
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Stoklas, R Gregušová, D Blaho, M Fröhlich, K Novák, J Matys, M Zenji Yatabe Kordoš, P Hashizume, T
Published in
Semiconductor Science and Technology
The electrical properties of AlGaN/GaN MOSHFETs with HfO2 prepared by atomic layer deposition with and w/o oxygen-plasma treatment (further referred to as PHf-MOS and Hf-MOS) were investigated. The sub-threshold slope of the MOSHFETs (350 and 150 mV dec−1 for Hf-MOS and PHf-MOS, respectively) were lower than that for HFET (450 mV dec−1), which also...
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Tanoue, Hironobu Takenouchi, Masato Yamashita, Tatsuya Wada, Shohei Zenji Yatabe Nagaoka, Shoji Naka, Yoshihiro Nakamura, Yusui
Published in
physica status solidi (a)
The crystal quality of ZnO films grown by mist chemical vapor deposition (mist‐CVD) was improved by introducing ZnO buffer layers on sapphire substrates. The ZnO films were grown by high‐speed rotation‐type mist‐CVD with a ZnCl2 aqueous solution, which provided uniform epitaxial layers over 2‐inch wafers. To grow the ZnO buffer layers, it is necess...
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Matys, M. Adamowicz, B. Domanowska, A. Michalewicz, A. Stoklas, R. Akazawa, M. Zenji Yatabe Hashizume, T.
Published in
Journal of Applied Physics
The energy spectrum of interface state density, Dit(E), was determined at oxide/III-N heterojunction interfaces in the entire band gap, using two complementary photo-electric methods: (i) photo-assisted capacitance-voltage technique for the states distributed near the midgap and the conduction band (CB) and (ii) light intensity dependent photo-capa...
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Zenji Yatabe Tsuda, Takaaki Matsushita, Junya Sato, Takehide Otabe, Tatsuya Sue, Koji Nagaoka, Shoji Nakamura, Yusui
Published in
physica status solidi (c)
Tin dioxide (SnO2) thin films, as a candidate for realizing next‐generation electrical and optical devices, were grown on 2‐inch diameter m ‐plane sapphire substrates by mist chemical vapour deposition at atmospheric pressure. The SnO2 thin films were characterized by scanning electron microscope (SEM), atomic force microscope (AFM), X‐ray diffract...
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Kaneki, Shota Ohira, Joji Toiya, Shota Zenji Yatabe Asubar, Joel T. Hashizume, Tamotsu
Published in
Applied Physics Letters
Interface characterization was carried out on Al2O3/GaN structures using epitaxial n-GaN layers grown on free-standing GaN substrates with relatively low dislocation density (
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Zenji Yatabe Asubar, Joel T Hashizume, Tamotsu
Published in
Journal of Physics D: Applied Physics
Recent years have witnessed GaN-based devices delivering their promise of unprecedented power and frequency levels and demonstrating their capability as an able replacement for Si-based devices. High-electron-mobility transistors (HEMTs), a key representative architecture of GaN-based devices, are well-suited for high-power and high frequency devic...
