Yuya Yamaoka - Academia.edu (original) (raw)

Papers by Yuya Yamaoka

Research paper thumbnail of Relationship between Al content of AlGaN buffer layer on top of initial AlN nucleation layer on Si and vertical leakage current of AlGaN/GaN high-electron-mobility transistor structures

2016 Compound Semiconductor Week (CSW) [Includes 28th International Conference on Indium Phosphide & Related Materials (IPRM) & 43rd International Symposium on Compound Semiconductors (ISCS), 2016

Research paper thumbnail of Relationship between Al compositions of AlGaN buffer layer and vertical leakage current of AlGaN/GaN HEMT on Si substrate

The Japan Society of Applied Physics, 2016

Research paper thumbnail of Challenges and opportunities of MOVPE and THVPE/HVPE for nitride light emitting device

Light-Emitting Devices, Materials, and Applications XXIV, 2020

Challenges and opportunities of MOVPE and THVPE/HVPE for nitride light emitting devices are discu... more Challenges and opportunities of MOVPE and THVPE/HVPE for nitride light emitting devices are discussed. Attempts to grow uniform and high quality epitaxial layers for both visible and UV range are presented. In order to examine the possibility of using a bulk GaN substrate, cost parity condition of GaN on GaN LED compared with LED on sapphire is presented in terms of a lumen per dollar. It is important to improve through-put of HVPE for GaN substrate manufacturing. Tri-halide VPE (THVPE) is introduced as a newly evolving technology with a high growth rate of 300μm/h at a high growth temperature of 1250ºC, which may replace HVPE for a bulk GaN substrate. Economical consideration of the comparison of HVPE and THVPE is discussed. Regarding UVC LEDs, there is an option to use a high quality AlN template on sapphire which is fabricated by 1700ºC annealing at nitrogen with a face to face configuration. Possible cost reduction and remaining issue are described.

Research paper thumbnail of The relationship between the vertical-direction leakage current of AlN on Si substrate and the type of dislocation in AlN layer

The Japan Society of Applied Physics, 2017

The relationship between the vertical-direction leakage current of AlN on Si substrate and the ty... more The relationship between the vertical-direction leakage current of AlN on Si substrate and the type of dislocation in AlN layer 山岡 優哉 , 各務 憲 ,生方 映徳 , 矢野 良樹 , 田渕 俊也 , 松本 功 1 江川 孝志 2 (1.大陽日酸株式会社 2.名古屋工業大学) Yuya Yamaoka , Ken Kakamu, Akinori Ubukata, Yoshiki Yano, Toshiya Tabuchi, Koh Matsumoto, Takashi Egawa 2 (1.Taiyo Nippon Sanso Corp., 2.Nagoya Institute of Technology) E-mail: Yuya.Yamaoka@tn-sanso.co.jp

Research paper thumbnail of Mapping of Ni/AlGaN/GaN Schottky contacts on Si substrates using scanning internal photoemission microscopy

The Japan Society of Applied Physics, 2017

Research paper thumbnail of The influence of number of strained-layer super-lattice (SLS) periods in vertical direction breakdown voltage of AlGaN/GaN high-electron-mobility transistor on Si substrates

The Japan Society of Applied Physics, 2016

Research paper thumbnail of Optimization of p-Cladding Layer for Improvement of Deep Ultraviolet Light Emitting Diode performance

The Japan Society of Applied Physics, 2019

Research paper thumbnail of Influence of MOCVD reactor environment on AlGaN/GaN HEMT growth on Si

Influence of MOCVD reactor environment on AlGaN/GaN HEMT growth on Si 山岡 優哉 , 生方 映徳 , 矢野 良樹 , 田渕 ... more Influence of MOCVD reactor environment on AlGaN/GaN HEMT growth on Si 山岡 優哉 , 生方 映徳 , 矢野 良樹 , 田渕 俊也 , 松本 功 1 江川 孝志 2 (1.大陽日酸株式会社 2.名古屋工業大学) Yuya Yamaoka , Akinori Ubukata, Yoshiki Yano, Toshiya Tabuchi, Koh Matsumoto, and Takashi Egawa 2 (1.Taiyo Nippon Sanso Corp., 2.Nagoya Institute of Technology) E-mail: Yuya.Yamaoka@tn-sanso.co.jp まえがき Si 基板上 AlGaN/GaN HEMT は高出力、低価格次世代パワーデバイスとして普及が期待さ れているが、Si 基板等のヘテロ界面から発生する貫通転移由来の縦方向リーク電流がデバイス信頼性 を損なう点が課題となっている。我々はこれまで、GaN/Si 界面の成長プロセスとリーク電流の関係性 について調査を行ってきた。その結果、成長初期層である AlN 核形成層の結晶品質との関係性が非常 に強いことが明らかとなっている[1-3]。加えて、洗浄残渣が検出されなかった炉内部品を使用して成 長した AlN 核形成層の結晶品質は洗浄残渣が検出された炉内部品の場合とくらべ改善することが明ら かとなっている[4]。そこで、本研究では洗浄残渣による AlN 核形成層結晶品質悪化の原因の追及する ために、MOCVD 炉に基板を搬入した時点の炉内環境と Si 基板の表面状態との関係を調査した。 実験方法 MOCVD 装置は大陽日酸製 UR26K ( 8 inch ×6 枚炉)を使用した。炉内部品は洗浄残渣が付 着したものを使用した。基板搬入前に以下のような 3 通りのベーキングを行い炉内環境を制御した。 処理 1) ベーキングなし、処理 2) 水素ベーキング (1025 °C 、31 min), 処理 3) AlN 成長後水素ベーキ ング、の 3 条件である。使用した Si 基板は基板直径、200 mm、 面方位 (111)、P 型、基板厚、1 mm である。各条件にてベーキングした後に、MOCVD 炉内...

Research paper thumbnail of Investigation of high temperature N 2 annealing of AlN on 6-inch

Research paper thumbnail of Temperature dependence of vertical leakage current in AlGaN/GaN high-electron-mobility transistor on Si substrates

The Japan Society of Applied Physics, 2017

Research paper thumbnail of Defect Observations of Ni/AlGaN/GaN Schottky Contacts on Si Substrates Using Scanning Internal Photoemission Microscopy

Extended Abstracts of the 2017 International Conference on Solid State Devices and Materials, 2017

Research paper thumbnail of Effect of threading dislocation in an AlN nucleation layer and vertical leakage current in an AlGaN/GaN high-electron mobility transistor structure on a silicon substrate

Semiconductor Science and Technology, 2018

We used conductive atomic force microscopy (C-AFM) and aqueous potassium hydroxide (KOH) solution... more We used conductive atomic force microscopy (C-AFM) and aqueous potassium hydroxide (KOH) solution etching to investigate the origin of vertical leakage current through an AlN nucleation layer in AlGaN/GaN high-electron mobility transistors (HEMTs) grown on a Si substrate. The micro area vertical leakage current in the AlN nucleation layer was observed in the presence of large hexagonally shaped etch pits (Each etch pit was about 1 μm in diameter) using C-AFM measurements after KOH etching. It is considered that large hexagonally shaped etch pits originate from screw-type dislocations from the etch pit shape. Vertical leakage current in the AlN nucleation layer increased by two orders of magnitude with increasing density of large hexagonally shaped etch pits in the AlN nucleation layer. Consequently, with increased vertical leakage current in the AlN nucleation layer, the vertical leakage current in the HEMT structure also increased. These results indicate that screw-type threading dislocations in AlN nucleation layers creates the vertical leakage current path in HEMT structures on Si substrates.

Research paper thumbnail of Discrete-Pulsed Current Time Method to Estimate Channel Thermal Resistance of GaN-Based Power Devices

IEEE Transactions on Electron Devices, 2018

Research paper thumbnail of Effect of the formation temperature of the AlN/Si interface on the vertical-direction breakdown voltages of AlGaN/GaN HEMTs on Si substrates

MRS Advances, 2016

In this study, the initial AlN layer and the vertical-direction breakdown voltage (VDBV) of AlGaN... more In this study, the initial AlN layer and the vertical-direction breakdown voltage (VDBV) of AlGaN/GaN high-electron-mobility transistors (HEMTs) were characterized. Prior to the formation of the interface between the AlN layer and the Si substrate, only trimethylaluminum (TMA) was introduced without ammonia to control the crystal quality of initial AlN layer (TMA preflow). HEMT structures were simultaneously grown on identical AlN layers on Si substrates (AlN/Si templates) grown using different TMA preflow temperatures. The density of screw- or mixed-type dislocations in the initial AlN layer decreased as the TMA preflow temperature increased. Further, the VDBV of the HEMT structure increased as the TMA preflow temperature increased. It is supposed that the screw- or mixed-type dislocations are the possible source of the vertical leakage current in the HEMT structures. The improvement in the crystal quality of the initial AlN layer affects the increase in the VDBV of the AlGaN/GaN H...

Research paper thumbnail of Impact of the AlN nucleation layer on the variation of the vertical-direction breakdown voltage of AlGaN/GaN high-electron-mobility transistor structures on a Si substrate

physica status solidi (a), 2017

Research paper thumbnail of Influence of AlN nucleation layer on vertical breakdown characteristics for GaN-on-Si

physica status solidi (a), 2015

A study of metal‐organic chemical vapor deposition (MOCVD) grown AlN nucleation layer (NL) on bre... more A study of metal‐organic chemical vapor deposition (MOCVD) grown AlN nucleation layer (NL) on breakdown characteristics for GaN‐on‐Si is presented. It is widely believed that AlN NL can act as an insulator because of its large band gap ∼6.2 eV. On contrary, this study of AlN NL/Si reveals conductive nature and shows high vertical leakage. The structural examinations along with electrical characterization show AlN NL/Si quality depends on the growth temperature. The surface morphology and presence of unintentional oxygen impurities govern the vertical leakage of AlN NL/Si. Interestingly, the AlN NL influences the growth of subsequent epitaxial layers as well as their vertical breakdown voltages (BVs). Further, it is found that AlGaN intermediate layer and multipairs of AlGaN/AlN strained layer superlattice (SLS) grown over AlN NL with better surface properties enhances the vertical BV. A high BV of 1.3 kV is achieved for SLS multipairs with a total thickness of 4.4 μm and the translated breakdown field strength is 2.8 MV cm−1 for MOCVD grown GaN‐on‐Si.

Research paper thumbnail of Influence of the Al content of the AlGaN buffer layer in AlGaN/GaN high-electron-mobility transistor structures on a Si substrate

physica status solidi (a), 2017

Research paper thumbnail of Opportunities and challenges in GaN metal organic chemical vapor deposition for electron devices

Japanese Journal of Applied Physics, 2016

Research paper thumbnail of Normally-OFF Al2O3/AlGaN/GaN MOS-HEMT on 8 in. Si with Low Leakage Current and High Breakdown Voltage (825 V)

Applied Physics Express, 2014

Research paper thumbnail of High growth rates of AlN and AlGaN on 8″ silicon wafer using metal-organic vapor phase epitaxy reactor

physica status solidi (c), 2013

Research paper thumbnail of Relationship between Al content of AlGaN buffer layer on top of initial AlN nucleation layer on Si and vertical leakage current of AlGaN/GaN high-electron-mobility transistor structures

2016 Compound Semiconductor Week (CSW) [Includes 28th International Conference on Indium Phosphide & Related Materials (IPRM) & 43rd International Symposium on Compound Semiconductors (ISCS), 2016

Research paper thumbnail of Relationship between Al compositions of AlGaN buffer layer and vertical leakage current of AlGaN/GaN HEMT on Si substrate

The Japan Society of Applied Physics, 2016

Research paper thumbnail of Challenges and opportunities of MOVPE and THVPE/HVPE for nitride light emitting device

Light-Emitting Devices, Materials, and Applications XXIV, 2020

Challenges and opportunities of MOVPE and THVPE/HVPE for nitride light emitting devices are discu... more Challenges and opportunities of MOVPE and THVPE/HVPE for nitride light emitting devices are discussed. Attempts to grow uniform and high quality epitaxial layers for both visible and UV range are presented. In order to examine the possibility of using a bulk GaN substrate, cost parity condition of GaN on GaN LED compared with LED on sapphire is presented in terms of a lumen per dollar. It is important to improve through-put of HVPE for GaN substrate manufacturing. Tri-halide VPE (THVPE) is introduced as a newly evolving technology with a high growth rate of 300μm/h at a high growth temperature of 1250ºC, which may replace HVPE for a bulk GaN substrate. Economical consideration of the comparison of HVPE and THVPE is discussed. Regarding UVC LEDs, there is an option to use a high quality AlN template on sapphire which is fabricated by 1700ºC annealing at nitrogen with a face to face configuration. Possible cost reduction and remaining issue are described.

Research paper thumbnail of The relationship between the vertical-direction leakage current of AlN on Si substrate and the type of dislocation in AlN layer

The Japan Society of Applied Physics, 2017

The relationship between the vertical-direction leakage current of AlN on Si substrate and the ty... more The relationship between the vertical-direction leakage current of AlN on Si substrate and the type of dislocation in AlN layer 山岡 優哉 , 各務 憲 ,生方 映徳 , 矢野 良樹 , 田渕 俊也 , 松本 功 1 江川 孝志 2 (1.大陽日酸株式会社 2.名古屋工業大学) Yuya Yamaoka , Ken Kakamu, Akinori Ubukata, Yoshiki Yano, Toshiya Tabuchi, Koh Matsumoto, Takashi Egawa 2 (1.Taiyo Nippon Sanso Corp., 2.Nagoya Institute of Technology) E-mail: Yuya.Yamaoka@tn-sanso.co.jp

Research paper thumbnail of Mapping of Ni/AlGaN/GaN Schottky contacts on Si substrates using scanning internal photoemission microscopy

The Japan Society of Applied Physics, 2017

Research paper thumbnail of The influence of number of strained-layer super-lattice (SLS) periods in vertical direction breakdown voltage of AlGaN/GaN high-electron-mobility transistor on Si substrates

The Japan Society of Applied Physics, 2016

Research paper thumbnail of Optimization of p-Cladding Layer for Improvement of Deep Ultraviolet Light Emitting Diode performance

The Japan Society of Applied Physics, 2019

Research paper thumbnail of Influence of MOCVD reactor environment on AlGaN/GaN HEMT growth on Si

Influence of MOCVD reactor environment on AlGaN/GaN HEMT growth on Si 山岡 優哉 , 生方 映徳 , 矢野 良樹 , 田渕 ... more Influence of MOCVD reactor environment on AlGaN/GaN HEMT growth on Si 山岡 優哉 , 生方 映徳 , 矢野 良樹 , 田渕 俊也 , 松本 功 1 江川 孝志 2 (1.大陽日酸株式会社 2.名古屋工業大学) Yuya Yamaoka , Akinori Ubukata, Yoshiki Yano, Toshiya Tabuchi, Koh Matsumoto, and Takashi Egawa 2 (1.Taiyo Nippon Sanso Corp., 2.Nagoya Institute of Technology) E-mail: Yuya.Yamaoka@tn-sanso.co.jp まえがき Si 基板上 AlGaN/GaN HEMT は高出力、低価格次世代パワーデバイスとして普及が期待さ れているが、Si 基板等のヘテロ界面から発生する貫通転移由来の縦方向リーク電流がデバイス信頼性 を損なう点が課題となっている。我々はこれまで、GaN/Si 界面の成長プロセスとリーク電流の関係性 について調査を行ってきた。その結果、成長初期層である AlN 核形成層の結晶品質との関係性が非常 に強いことが明らかとなっている[1-3]。加えて、洗浄残渣が検出されなかった炉内部品を使用して成 長した AlN 核形成層の結晶品質は洗浄残渣が検出された炉内部品の場合とくらべ改善することが明ら かとなっている[4]。そこで、本研究では洗浄残渣による AlN 核形成層結晶品質悪化の原因の追及する ために、MOCVD 炉に基板を搬入した時点の炉内環境と Si 基板の表面状態との関係を調査した。 実験方法 MOCVD 装置は大陽日酸製 UR26K ( 8 inch ×6 枚炉)を使用した。炉内部品は洗浄残渣が付 着したものを使用した。基板搬入前に以下のような 3 通りのベーキングを行い炉内環境を制御した。 処理 1) ベーキングなし、処理 2) 水素ベーキング (1025 °C 、31 min), 処理 3) AlN 成長後水素ベーキ ング、の 3 条件である。使用した Si 基板は基板直径、200 mm、 面方位 (111)、P 型、基板厚、1 mm である。各条件にてベーキングした後に、MOCVD 炉内...

Research paper thumbnail of Investigation of high temperature N 2 annealing of AlN on 6-inch

Research paper thumbnail of Temperature dependence of vertical leakage current in AlGaN/GaN high-electron-mobility transistor on Si substrates

The Japan Society of Applied Physics, 2017

Research paper thumbnail of Defect Observations of Ni/AlGaN/GaN Schottky Contacts on Si Substrates Using Scanning Internal Photoemission Microscopy

Extended Abstracts of the 2017 International Conference on Solid State Devices and Materials, 2017

Research paper thumbnail of Effect of threading dislocation in an AlN nucleation layer and vertical leakage current in an AlGaN/GaN high-electron mobility transistor structure on a silicon substrate

Semiconductor Science and Technology, 2018

We used conductive atomic force microscopy (C-AFM) and aqueous potassium hydroxide (KOH) solution... more We used conductive atomic force microscopy (C-AFM) and aqueous potassium hydroxide (KOH) solution etching to investigate the origin of vertical leakage current through an AlN nucleation layer in AlGaN/GaN high-electron mobility transistors (HEMTs) grown on a Si substrate. The micro area vertical leakage current in the AlN nucleation layer was observed in the presence of large hexagonally shaped etch pits (Each etch pit was about 1 μm in diameter) using C-AFM measurements after KOH etching. It is considered that large hexagonally shaped etch pits originate from screw-type dislocations from the etch pit shape. Vertical leakage current in the AlN nucleation layer increased by two orders of magnitude with increasing density of large hexagonally shaped etch pits in the AlN nucleation layer. Consequently, with increased vertical leakage current in the AlN nucleation layer, the vertical leakage current in the HEMT structure also increased. These results indicate that screw-type threading dislocations in AlN nucleation layers creates the vertical leakage current path in HEMT structures on Si substrates.

Research paper thumbnail of Discrete-Pulsed Current Time Method to Estimate Channel Thermal Resistance of GaN-Based Power Devices

IEEE Transactions on Electron Devices, 2018

Research paper thumbnail of Effect of the formation temperature of the AlN/Si interface on the vertical-direction breakdown voltages of AlGaN/GaN HEMTs on Si substrates

MRS Advances, 2016

In this study, the initial AlN layer and the vertical-direction breakdown voltage (VDBV) of AlGaN... more In this study, the initial AlN layer and the vertical-direction breakdown voltage (VDBV) of AlGaN/GaN high-electron-mobility transistors (HEMTs) were characterized. Prior to the formation of the interface between the AlN layer and the Si substrate, only trimethylaluminum (TMA) was introduced without ammonia to control the crystal quality of initial AlN layer (TMA preflow). HEMT structures were simultaneously grown on identical AlN layers on Si substrates (AlN/Si templates) grown using different TMA preflow temperatures. The density of screw- or mixed-type dislocations in the initial AlN layer decreased as the TMA preflow temperature increased. Further, the VDBV of the HEMT structure increased as the TMA preflow temperature increased. It is supposed that the screw- or mixed-type dislocations are the possible source of the vertical leakage current in the HEMT structures. The improvement in the crystal quality of the initial AlN layer affects the increase in the VDBV of the AlGaN/GaN H...

Research paper thumbnail of Impact of the AlN nucleation layer on the variation of the vertical-direction breakdown voltage of AlGaN/GaN high-electron-mobility transistor structures on a Si substrate

physica status solidi (a), 2017

Research paper thumbnail of Influence of AlN nucleation layer on vertical breakdown characteristics for GaN-on-Si

physica status solidi (a), 2015

A study of metal‐organic chemical vapor deposition (MOCVD) grown AlN nucleation layer (NL) on bre... more A study of metal‐organic chemical vapor deposition (MOCVD) grown AlN nucleation layer (NL) on breakdown characteristics for GaN‐on‐Si is presented. It is widely believed that AlN NL can act as an insulator because of its large band gap ∼6.2 eV. On contrary, this study of AlN NL/Si reveals conductive nature and shows high vertical leakage. The structural examinations along with electrical characterization show AlN NL/Si quality depends on the growth temperature. The surface morphology and presence of unintentional oxygen impurities govern the vertical leakage of AlN NL/Si. Interestingly, the AlN NL influences the growth of subsequent epitaxial layers as well as their vertical breakdown voltages (BVs). Further, it is found that AlGaN intermediate layer and multipairs of AlGaN/AlN strained layer superlattice (SLS) grown over AlN NL with better surface properties enhances the vertical BV. A high BV of 1.3 kV is achieved for SLS multipairs with a total thickness of 4.4 μm and the translated breakdown field strength is 2.8 MV cm−1 for MOCVD grown GaN‐on‐Si.

Research paper thumbnail of Influence of the Al content of the AlGaN buffer layer in AlGaN/GaN high-electron-mobility transistor structures on a Si substrate

physica status solidi (a), 2017

Research paper thumbnail of Opportunities and challenges in GaN metal organic chemical vapor deposition for electron devices

Japanese Journal of Applied Physics, 2016

Research paper thumbnail of Normally-OFF Al2O3/AlGaN/GaN MOS-HEMT on 8 in. Si with Low Leakage Current and High Breakdown Voltage (825 V)

Applied Physics Express, 2014

Research paper thumbnail of High growth rates of AlN and AlGaN on 8″ silicon wafer using metal-organic vapor phase epitaxy reactor

physica status solidi (c), 2013