Achievements

Academic Achievements 　※Past 5-Years

＜Peer-Reviewed Papers＞

1. Masanobu Takahashi, Hitoshi Takane, Hiroko Iguchi, Tetsuo Narita, Kenji Ito, and Masamichi Akazawa; "Sub-bandgap-light-assisted capacitance–voltage study of gap states near valence band maximums at AlSiO/GaN interfaces with and without an AlN interfacial layer," J. Appl. Phys. Vol. 139, pp. 194502-1 – 12 (2026). 

2. Masanobu Takahashi, Takahiro Shimazaki, Taketomo Sato, and Masamichi Akazawa; "Possible Origin of Near-Interface Donor-Like Defects in p-Type Gallium Nitride Metal–Oxide–Semiconductor Structures," physica status solidi (a), 9 pages (2026). 

3. Y. Luo, Y. Hatakeyama, H. Karasawa, and M. Akazawa; "Effects of 600 °C annealing prior to activation annealing of Mg-ion-implanted GaN on subsequently formed MOS interfaces," Jpn. J. Appl. Phys. Vol. 65, pp. 026502-1 – 8 (2026). 

4. Y. Hatakeyama, T. Narita, T. Kachi, and M. Akazawa; "Detection of charge transition level of near-surface hydrogen interstitials introduced into Mg-ion-implanted GaN by annealing," Jpn. J. Appl. Phys. Vol. 64, pp. 090905-1 – 5 (2025). 

5. G. Shindo, Y. Hatakeyama, H. Fujikura, S. Kaneki, M. Yokoyama, F. Horikiri, and M. Akazawa; " Effects of 850 °C annealing on near-surface defects in Mg-ion-implanted GaN examined using MOS structures," AIP Advances, Vol. 15, pp. 085007-1 – 7 (2025).

6. M. Takahashi, Y. Jiao, and M. Akazawa; "Effects of SiO2 cap annealing at 800 ℃ on Ga-polar n-type and p-type GaN (0001) surfaces compared by X-ray photoelectron spectroscopy," Jpn. J. Appl. Phys. Vol. 63, pp. 110905-1 – 4 (2024).

7. Y. Jiao, M. Takahashi, T. Sato, and M. Akazawa; "Effects of SiO2 cap annealing on MOS interfaces formed on Mg-doped p-type GaN surface," Jpn. J. Appl. Phys. Vol. 63, pp. 09SP19-1 – 6 (2024).

8. Y. Jiao, T. Nukariya, U. Takatsu, T. Narita, T. Kachi, T. Sato, and M. Akazawa; "Reduction in Gap State Density near Valence Band Edge at Al2O3/p-type GaN Interface by Photoelectrochemical Etching and Subsequent SiO2 Cap Annealing," Phys. Status Solidi B, Vol. 261, pp. 2400025-1 – 9 (2024).

9. Y. Luo, Y. Hatakeyama, and M. Akazawa; "Effects of low-temperature annealing on net doping profile of Mg-ion-implanted GaN studied by MOS capacitance–voltage measurement," Jpn. J. Appl. Phys. Vol. 62, pp. 126501-1 – 6 (2023).

10. R. Ochi, T. Togashi, Y. Osawa, F. Horikiri, H. Fujikura, K. Fujikawa, T. Furuya, R. Isono, M. Akazawa, and T. Sato; "Investigation of dominance in near-surface region on electrical properties of AlGaN/GaN heterostructures using TLM, XPS, and PEC etching techniques," accepted for publication in Appl. Phys. Express (2023).

11. Y. Hatakeyama, T. Narita, M. Bockowski, T. Kachi, and M. Akazawa; "Investigation of gap states near conduction band edge in vicinity of interface between Mg-ion-implanted GaN and Al2O3 deposited after ultra-high-pressure annealing," Jpn. J. Appl. Phys. Vol. 62, pp. SN1002-1 – 7 (2023).

12. Y. Hatakeyama and M. Akazawa; "Interface state density distribution near conduction band edge at Al2O3/Mg-ion-implanted GaN interface formed after activation annealing using AlN cap layer," AIP Advances, Vol. 12, pp. 125224-1 – 7 (2022).

13. M. Akazawa, Y. Tamamura, T. Nukariya, K. Kubo, T. Sato, T. Narita, and T. Kachi; "Detection of defect levels in vicinity of Al2O3/p-type GaN interface using sub-bandgap-light-assisted capacitance–voltage method," J. Appl. Phys. Vol. 132, pp. 195302-1 – 10 (2022).

14. M. Akazawa, S. Murai, and T. Kachi; "Encapsulant‑Dependent Effects of Long‑Term Low‑Temperature Annealing on Interstitial Defects in Mg‑Ion‑Implanted GaN," J. Electron. Mater. Vol. 51, pp. 1731 – 1739 (2022).

＜ Presentations at International Conferences＞

1. Hiroto Akabane, Hinata Karasawa, Masanobu Takahashi, and Masamichi Akazawa; "Inversion-type GaN MOSFETs Fabricated by Applying Long-term 300°C Annealing Simultaneously to MOS Interfaces and Ohmic Contacts," Compound Semiconductor Week 2026 (CSW2026, Kumamoto-Jo Hall, Kumamoto, Japan, May 24–28, 2026). 

2. H. Karasawa, M. Takahashi, and M. Akazawa; "Effects of long-term 850℃ pre-annealing prior to rapid activation annealing at 1250℃ on Mg-ion implanted GaN studied by using MOS structures," 18th International Symposium on Advanced Plasma Science and its Applications for Nitrides and Nanomaterials/ 19th International Conference on Plasma-Nano Technology & Science (ISPlasma2026/IC-PLANTS2026, Meijo University, Nagoya, Aichi, Japan, March 2–6, 2026). 

3. M. Takahashi, Y. Jiao, and M. Akazawa; "Investigation of GaN MOS structures with SiO2 formed by atomic layer deposition using bis (ethyl-methyl-amino) silane and ozone," 15th International Conference on Nitride Semiconductors (ICNS-15, Clarion Hotel Malmö Live, Malmö, Sweden, July 6–11, 2025).

4. M. Akazawa, M. Takahashi, K. Itoh, and T. Narita; "Suppression of hole injection into near-interface traps by inserting AlN interfacial layer between AlSiO and GaN," 15th International Conference on Nitride Semiconductors (ICNS-15, Clarion Hotel Malmö Live, Malmö, Sweden, July 6–11, 2025).

5. M. Akazawa, G. Shindo, and M. Takahashi; "Effects of Pre-Annealing at 850 ℃ Using AlON Cap Layer on Properties of GaN MOS Interfaces," Compound Semiconductor Week 2025 (CSW2025, Banff Centre for Arts and Creativity, Banff, Alberta, Canada, May 27–30, 2025). 

6. M. Takahashi, Y. Jiao, and M. Akazawa; "Reduction of positive fixed charges at Al2O3/p-GaN interface by pre-annealing using AlON cap layer," 17th International Symposium on Advanced Plasma Science and its Applications for Nitrides and Nanomaterials/ 18th International Conference on Plasma-Nano Technology & Science (ISPlasma2025/IC-PLANTS2025, Chubu University, Kasugai, Aichi, Japan, March 3–7, 2025). 

7. Y. Jiao, M. Takahashi, and M. Akazawa; "X-Ray Photoelectron Spectroscopy Monitoring of Fermi Level Position at Mg-Doped p-Type GaN Surface During MOS Interface Formation," 32nd International Colloquium on Scanning Probe Microscopy (ICSPM32, Hotel Monterey Edelhof Sapporo, Sapporo, Japan, Nov. 18–20, 2024).

8. Y. Luo, Y. Hatakeyama, and M. Akazawa; "Effects of Long-Term Low-Temperature Annealing Prior to Activation Annealing on Near-Conduction-Band-Edge Gap States in Vicinity of Mg-Ion-Implanted GaN Surface," 32nd International Colloquium on Scanning Probe Microscopy (ICSPM32, Hotel Monterey Edelhof Sapporo, Sapporo, Japan, Nov. 18–20, 2024).

9. M. Akazawa, Y. Jiao, M. Takahashi, T. Shimazaki, and T. Sato; "Investigation of Charges Originated from Near-Surface Defects in p-type GaN Using X-ray Photoelectron Spectroscopy and MOS Diodes," International Workshop on Nitride Semiconductors 2024 (IWN2024, Hilton Hawaiian Village, O’ahu, Hawai’i, USA, Nov. 3–8, 2024). 

10. G. Shindo, Y. Hatakeyama, and M. Akazawa; "Effects of Moderate-Temperature Annealing on Near-Surface Defects in Mg-Implanted GaN Studied Using MOS Structures," 2024 International Conference on Solid State Devices and Materials (SSDM2024, Arcrea Himeji, Himeji, Hyogo, Japan, Sept. 1–4, 2024). 

11. M. Akazawa, Y. Jiao, M. Takahashi, T. Shimazaki, and T. Sato; "Effects of Annealing at 800 ℃ on SiO2/GaN Interfaces Studied by X-ray Photoelectron Spectroscopy," Compound Semiconductor Week 2024 (CSW2024, Lund University, Lund, Sweden, June 3–6, 2024). 

12. Yining Jiao, Takahide Nukariya, Umi Takatsu, Taketomo Sato, and Masamichi Akazawa; "Effects of SiO2-Cap Annealing Prior to Interface Formation on Properties of Al2O3/p-type GaN Interfaces," 16th International Symposium on Advanced Plasma Science and its Applications for Nitrides and Nanomaterials / 17th International Conference on Plasma-Nano Technology & Science / 13th Asia-Pacific International Symposium on the Basics and Applications of Plasma Technology (ISPlasma2024/IC-PLANTS2024/APSPT-13, Nagoya University, Nagoya, Japan, March 3–7, 2024). 

13. Y. Hatakeyama, Y. Luo, G. Shindo, and M. Akazawa; "MOS-structure based study of defects in Mg-ion-implanted GaN," International Conference on Materials and Systems for Sustainability (ICMaSS2023, Nagoya University, Nagoya, Japan, December 1-3, 2023). 

14. Y. Hatakeyama, G. Shindo, Y. Luo, and M. Akazawa; "Detection of Gap States Originated from Ga-Interstitial and Divacancy Defects in Mg-Implanted GaN Using MOS Structures," 14th International Conference on Nitride Semiconductors (ICNS-14, Hilton Fukuoka Sea Hawk, Fukuoka, Japan, November 12-17, 2023).

15. T. Nukariya, Y. Jiao, U. Takatsu, T. Sato, and M. Akazawa; "Interface Properties of p-type GaN MOS Structures Examined by Sub-Bandgap-Light-Assisted Capacitance–Voltage Measurement," 14th International Conference on Nitride Semiconductors (ICNS-14, Hilton Fukuoka Sea Hawk, Fukuoka, Japan, November 12-17, 2023).

16. T. Hashizume and M. Akazawa; "MOS interface technologies for high-power and high-frequency GaN transistors (invited)," 14th International Conference on Nitride Semiconductors (ICNS-14, Hilton Fukuoka Sea Hawk, Fukuoka, Japan, November 12-17, 2023).

17. M. Akazawa, Y. Luo, and Y. Hatakeyama; "Effects of Long-Term Low-Temperature Annealing on Lightly Mg-Implanted GaN," 21st International Workshop on Junction Technology (IWJT2023, Kyoto University, Kyoto, Japan, June 8-9, 2023). 

18. Y. Hatakeyama, M. Akazawa, T. Narita, M. Bockowski, and T. Kachi; "Impact of ultra-high-pressure annealing on interface state density distribution near conduction band at Al2O3/Mg-ion-implanted GaN interface," 15th International Symposium on Advanced Plasma Science and its Applications for Nitrides and Nanomaterials/ 16th International Conference on Plasma-Nano Technology & Science (ISPlasam2023/IC-PLANTS2023, Gifu University, Gifu, Japan, March 5–9, 2023). 

19. M. Akazawa, Y. Tamamura, T. Nukariya, K. Kubo, and T. Sato; " Impact of photoelectrochemical etching on Al2O3/p-GaN interface," International Workshop on Nitride Semiconductors 2022 (IWN2022, The Hotel Berlin Central District, Berlin, Germany, Oct. 9–14, 2022). 

20. Y. Tamamura, T. Nukariya, and M. Akazawa; "Photo-assisted C–V measurement of p-GaN MOS diodes," 14th International Symposium on Advanced Science and its Applications for Nitrides and Nanomaterials/15th International Conference on Plasma Nanotechnology and Science (ISPlasam2022/IC-PLANTS2022, Nagoya University, Online Meeting, March 6–10, 2022).