Publications

1. Effect of Ultra-Thin AlGaN Regrown Layer on the Electrical Properties of ZrO2/AlGaN/GaN Structures

Toi Nezu, Shogo Maeda, Ali Baratov, Suguru Terai, Kishi Sekiyama, Itsuki Nagase, Masaaki Kuzuhara, Akio Yamamoto, and Joel T. Asubar

Phys. Status Solidi A (2024) 2400073. https://doi.org/10.1002/pssa.202400073

2. Improved Performance of Normally-off GaN-based MIS-HEMTs with Recessed-gate and Ultrathin Regrown AlGaN Barrier

Shogo Maeda,  Shinsaku Kawabata, Itsuki Nagase, Ali Baratov, Masaki Ishiguro, Toi Nezu, Takahiro Igarashi, Kishi Sekiyama, Keito Shinohara, Melvin John F. Empizo, Nobuhiko Sarukura, Masaaki Kuzuhara, Akio Yamamoto, and Joel T. Asubar

Journal of Semiconductor Technology and Science 24, 25, 2024 , DOI 10.5573/JSTS.2024.24.1.25

3. MOVPE growth of AlGaN on RIE-treated GaN surfaces and its application to AlGaN/GaN electron devices (INVITED)

Akio Yamamoto, Ali Baratov, Masaaki Kuzuhara, and Joel T Asubar 

2023 IEEE IMFEDK Tech. Dig. doi: 10.1109/IMFEDK60983.2023.10366345

4. AlGaN/GaN Schottky-Gate HEMTs with low thermal budget V/Al/Mo/Au ohmic contacts

T Igarashi, S Maeda, A Baratov, JT Asubar, M Kuzuhara 

2023 IEEE IMFEDK Tech. Dig. doi: 10.1109/IMFEDK60983.2023.10366331

5. High performance normally-off recessed-gate GaN-based MIS-HEMTs achieved by oxygen plasma treatment

M Ishiguro, S Terai, K Sekiyama, S Urano, A Baratov, JT Asubar, M Kuzuhara 

2023 IEEE IMFEDK Tech. Dig. doi: 10.1109/IMFEDK60983.2023.10366337

6. Low thermal budget V/Al/Mo/Au ohmic contacts for improved performance of AlGaN/GaN MIS-HEMTs

Ali Baratov, Takahiro Igarashi, Masaki Ishiguro, Shogo Maeda, Terai Suguru, Masaaki Kuzuhara, Joel T Asubar

Japanese Journal of Applied Physics Rapid Communication 62, 110905, 2023 , DOI 10.35848/1347-4065/ad057a

7. An Accurate Approach to Develop Small Signal Circuit Models for AlGaN/GaN HEMTs using Rational Functions and Dependent Current Sources

Aakash Jadhav, Takashi Ozawa, Ali Baratov, Joel T Asubar, Masaaki Kuzuhara, Akio Wakejima, Shunpei Yamashita, Manato Deki, Shugo Nitta, Yoshio Honda, Hiroshi Amano, Sourajeet Roy, Biplab Sarkar

IEEE Journal of the Electron Devices, DOI 10.1109/JEDS.2022.3208028

8. Quasi-Normally-Off operation via Selective Area Growth in high-K-insulated GaN MIS-HEMTs 

S Maeda, JT Asubar, I Nagase, S Urano, T Nezu, T Igarashi, A Baratov, A Yamamoto, M Kuzuhara 

2022 IEEE IMFEDK Tech. Dig. doi: 10.1109/IMFEDK56875.2022.9975427

9. Effect of High-Temperature Annealed Al2O3 insulator on GaN MIS-HEMTs performance  

BDD Lau, S Yamazaki, S Urano, A Baratov, JT Asubar, M Kuzuhara  

2022 IEEE IMFEDK Tech. Dig. doi: 10.1109/IMFEDK56875.2022.9975407

10. Mist chemical vapor deposited-gate insulators for GaN-based MIS devices applications (Invited)

Zenji Yatabe, Yusui Nakamura, Joel T Asubar 

2022 IEEE IMFEDK Tech. Dig. doi: 10.1109/IMFEDK56875.2022.9975434

11. Improved Ohmic Contact Model for Accurate Simulation of GaN-based HEMTs Using Ensemble Monte Carlo Methods

K Sakota, K Herbert, K Shibata, M Kuzuhara, K Kodama, JT Asubar  

2022 IEEE IMFEDK Tech. Dig. doi: 10.1109/IMFEDK56875.2022.9975422

12. Effect of Oxygen plasma treatment on the performance of GaN-based MIS-HEMTs

K Sekiyama, M Ishiguro, S Yamazaki, S Urano, A Baratov, JT Asubar, M Kuzuhara 

2022 IEEE IMFEDK Tech. Dig. doi: 10.1109/IMFEDK56875.2022.9975436

13. Evidence of reduced interface states in Al2O3/AlGaN MIS structures via insertion of ex situ regrown AlGaN layer

Ali Baratov, Shinsaku Kawabata, Shun Urano, Itsuki Nagase, Masaki Ishiguro, Shogo Maeda, Takahiro Igarashi, Toi Nezu, Zenji Yatabe, Maciej Matys, Tetsu Kachi, Boguslawa Adamowicz, Akio Wakejima, Masaaki Kuzuhara, Akio Yamamoto and Joel T. Asubar
Applied Physics Express 15 104002-1 - 104002-5 Sept, 2022 

14. Modified Small Signal Circuit of AlGaN/GaN MOS-HEMTs Using Rational Functions

Aakash Jadhav, Takashi Ozawa, Ali Baratov, Joel T Asubar, Masaaki Kuzuhara, Akio Wakejima, Shunpei Yamashita, Manato Deki, Shugo Nitta, Yoshio Honda, Hiroshi Amano, Sourajeet Roy, Biplab Sarkar

IEEE Transactions on Electron Devices 68 6059-6064 Dec, 2021

15. Ornstein–Uhlenbeck process in a human body weight fluctuation

Z Yatabe, JT Asubar

Physica A: Statistical Mechanics and its Applications 582 126286 Nov, 2021

16. Recessed gate GaN-based MIS-HEMTs with Al2O3 gate dielectric deposited by mist-CVD method

     M Ishiguro, S Urano, RS Low, M Faris, I Nagase, A Baratov, JT Asubar, T Motoyama, Y Nakamura, Z Yatabe, M Kuzuhara

     2021 IEEE IMFEDK Tech. Dig. doi: 10.1109/IMFEDK53601.2021.9637518

17. Mist chemical vapor deposited-Al2O3/AlGaN interfacial characterization for GaN MIS-HEMTs

     Tomohiro Motoyama, Zenji Yatabe, Yusui Nakamura, Ali Baratov, Rui Shan Low, Shun Urano, Joel T Asubar, Masaaki Kuzuhara

     2021 IEEE IMFEDK Tech. Dig. doi: 10.1109/IMFEDK53601.2021.9637625

18. Fabrication and Characterization of ZrO2/AlGaN/GaN MIS-HEMTs with regrown AlGaN Layer

     S Maeda, I Nagase, A Baratov, S Urano, JT Asubar, A Yamamoto, M Kuzuhara

     2021 IEEE IMFEDK Tech. Dig. doi: 10.1109/IMFEDK53601.2021.9637576

19. Electrical properties of GaN-based MIS-HEMTs with Al2O3 gate insulator deposited by ALD and mist-CVD techniques 

     S Urano, RS Low, M Faris, M Ishiguro, I Nagase, A Baratov, JT Asubar, T Motoyama, Y Nakamura, Z Yatabe, M Kuzuhara

     2021 IEEE IMFEDK Tech. Dig. doi: 10.1109/IMFEDK53601.2021.9637639

20. Stoichiometric imbalances in Mg-implanted GaN

Kai C Herbert, Kazuki Shibata, Joel T Asubar, Masaaki Kuzuhara

Japanese Journal of Applied Physics 60 066504 Jun, 2021

21. Generalized Frequency Dependent Small Signal Model for High Frequency Analysis of AlGaN/GaN MOS-HEMTs 

Aakash Jadhav, Takashi Ozawa, Ali Baratov, Joel T. Asubar, Masaaki Kuzuhara, Akio Wakejima, Shunpei Yamashita, Manato Deki, Yoshio Honda, Sourajeet Roy, Hiroshi Amano, Biplab Sarkar

IEEE Journal of Electron Devices 9 570 - 581 May, 2021

22. Controlling surface/interface states in GaN-based transistors: Surface model, insulated gate, and surface passivation (Invited, TOP  5 MOST READ PAPER in JOURNAL OF APPLIED PHYSICS April 2021)

Joel T. Asubar, Zenji Yatabe, Dagmar Gregusova, Tamotsu Hashizume

Journal of Applied Physics 129 121102-1 - 121102-28 Mar, 2021

23. GaN-based MIS-HEMTs with Al2O3 dielectric deposited by low-cost and environmental-friendly mist-CVD technique

(MOST READ PAPER March 2021)
Rui Shan Low, Joel T. Asubar, Ali Baratov, Shunsuke Kamiya, Itsuki Nagase, Shun Urano, Shinsaku Kawabata, Hirokuni Tokuda, Masaaki Kuzuhara, Yusui Nakamura, Kenta Naito, Tomihiro Motoyama, Zenji Yatabe
Applied Physics Express 14 031004-1 - 031004-5 Feb, 2021  Peer-reviewed

24. Design considerations for normally-off operation in Schottky gate p-GaN/AlGaN/GaN HEMTs
    Hirokuni Tokuda, Joel T. Asubar, Masaaki Kuzuhara
    Japanese Journal of Applied Physics 59 084002-1 - 084002-7 Jul 27, 2020  Peer-reviewed

25. Enhancement-Mode AlGaN/GaN MIS-HEMTs With High VTH and High IDmax Using Recessed-Structure With Regrown AlGaN Barrier

(Included in the "MOST POPULAR DOCUMENTS" April-June 2020, April 2021)
Joel T. Asubar, Shinsaku Kawabata, Hirokuni Tokuda, Akio Yamamoto, and Masaaki Kuzuhara
IEEE Electron Device Letters 41(5) 693 - 696 May, 2020  Peer-reviewed

26. Enhancement‐Mode AlGaN/GaN Vertical Trench Metal–Insulator–Semiconductor High‐Electron‐Mobility Transistors with a High Drain Current Fabricated Using the AlGaN Regrowth Technique
    Akio Yamamoto, Keito Kanatani, Norifumi Yoneda, Joel, T. Asubar, Hirokuni Tokuda, Masaaki Kuzuhara
    Physica Status Solidi A 217 1900622-1 - 1900622-7 Apr, 2020  Peer-reviewed

27. Epitaxial growth and characterization of Cr-doped ZnSnAs2 thin films on InP substrates
    Hiroto Oomae, Kai Sato, Miyuki Shinoda, M. I. Faris bin Ishak, Hideyuki Toyota, Masashi Akabori, Hidetoshi Kizaki, Shinichi Nakamura, Joel T. Asubar, Naotaka Uchitomi
    Japanese Journal of Applied Physics 59(3) 030601 - 030601 Mar 1, 2020  Peer-reviewed

28. Impact of SiN capping during Ohmic Annealing on Performance of GaN-based MISHEMTs
    RS Low, S Kawabata, JT Asubar, H Tokuda, M Kuzuhara
    2019 IEEE IMFEDK Technical Digest 77 - 78 Jan 9, 2020   Peer-reviewed

29. Influence of reactive-ion-etching depth on interface properties in Al2O3/n-GaN MOS diodes
    Hirokuni Tokuda, Sayaka Harada, Joel T. Asubar, Masaaki Kuzuhara
    Japanese Journal of Applied Physics 58 106503-1 - 106503-6 Sep, 2019  Peer-reviewed

30. On the presence of Ga2O sub-oxide in high-pressure water vapor annealed AlGaN surface by combined XPS and first-principles methods
    Mary Clare, S. Escaño, Joel T. Asubar, Zenji Yatabe, Melanie Y.David, Mutsunori Uenuma, Hirokuni Tokuda, Yukiharu Uraoka, Masaaki Kuzuhara, MasahikoTani
    Applied Surface Science 481 1120 - 1126 Jul, 2019  Peer-reviewed

31. Spatial distribution of substitutional Mn-As clusters in ferromagnetic (Zn,Sn,Mn)As2 thin films revealed by image reconstruction of atom probe tomography data 

(EDITOR's PICK)
Hiroto Oomae, Miyuki Shinoda, Joel T. Asubar, Kai Sato, Hideyuki Toyota, Norihito Mayama, Bakhshi Mehdiyev, Naotaka Uchitomi
Journal of Applied Physics 125 073902-1 - 073902-8 Feb, 2019  Peer-reviewed

32. Improved linearity, stability, and thermal performance of multi-mesa-channel AlGaN/GaN HEMTs

J. T. Asubar, H. Tokuda, M, Kuzuhara, Z. Yatabe, K. Nishiguchi, T. Hashizume

PISIKA - Journal of the Physics Society of the Philippines 1 11-1 - 11-6 Dec, 2018 

(INVITED)

33. Study on Threshold Voltage Hysteresis in GaN-Based Vertical Trench MOSFETs

S. Murata, M. Sasada, J. T. Asubar, H. Tokuda, K. Ueno, M. Edo, M. Kuzuhara

2018 IEEE IMFEDK Technical Digest 74 - 75 Dec, 2018  

34. Reduced Current Collapse in AIGaN/GaN HEMTs with p-GaN Layer in Gate-Drain Access Region

T. Ozawa, J. T. Asubar, H. Tokuda and, M. Kuzuhara

2018 IEEE IMFEDK Technical Digest 80 - 81 Dec, 2018  

35. Characterization of Resistivity and Breakdown Field in Fe-Doped Semi-Insulating Gan Substrates

A. Aoai, K. Suzuki, J. T. Asubar, H. Tokuda, K. Nojima, N. Ishibashi, N. Okada, K. Tadatomo, M. Kuzuhara

2018 IEEE IMFEDK Technical Digest 72 - 73 Dec, 2018 

36. Improved Current Collapse in AlGaN/GaN MOS-HEMTs with Dual Field-Plates

T. Nishitani, R. Yamaguchi, T. Yamazaki, J. T. Asubar, H. Tokuda, M. Kuzuhara

2018 IEEE IMFEDK Technical Digest 76 - 77 Dec, 2018 

37. Effect of Post-Gate Deposition Annealing on the Electrical Characteristics of AlGaN/GaN HEMTs with p-GaN Gate

S. Kawabata, J. T. Asubar, H. Tokuda, M. Kuzuhara

2018 IEEE IMFEDK Technical Digest 78 - 79 Dec, 2018

38. Electron concentration in highly resistive GaN substrates co-doped with Si, C, and Fe
    Hirokuni Tokuda, Kosuke Suzuki, Joel T. Asubar, Masaaki Kuzuhara
    Japanese Journal of Applied Physics 57 071001-1 - 071001-4 May, 2018  Peer-reviewed

39. Impact of rounded electrode corners on breakdown characteristics of AlGaN/GaN high-electron mobility transistors
    Taisei Yamazaki, Joel T. Asubar, Hirokuni Tokuda, Masaaki Kuzuhara
    Applied Physics Express 11(5) 054102-1 - 054102-5 May 1, 2018  Peer-reviewed

40. Magnetic phase change in Mn-doped ZnSnAs2 thin films depending on Mn concentration
    Naotaka Uchitomi, Shiro Hidaka, Shin Saito, Joel T. Asubar, Hideyuki Toyota
    Journal of Applied Physics 123(16) 161566-1 - 161566-7 Apr 28, 2018  Peer-reviewed

41. Analytical derivation of charge relaxation time distribution in transistor from current noise spectrum using inverse integral transformation method
    Zenji Yatabe, Shinya Inoue, Joel T. Asubar, Seiya Kasai
    Applied Physics Express 11(3) 031201-1 - 031201-4 Mar 1, 2018  Peer-reviewed

42. Correlation of AlGaN/GaN high-electron-mobility transistors electroluminescence characteristics with current collapse
    Shintaro Ohi, Taisei Yamazaki, Joel T. Asubar, Hirokuni Tokuda, Masaaki Kuzuhara
    Applied Physics Express 11(2) 024101-1 - 024101-14 Feb 1, 2018  Peer-reviewed

43. Analytical derivation of interface state density from sub-threshold swing in AlGaN/GaN metal- insulator- semiconductor high-electron-mobility transistors
    Hirokuni Tokuda, Joel T. Asubar, Masaaki Kuzuhara
    JAPANESE JOURNAL OF APPLIED PHYSICS 56(10) 104101-1 - 104101-5 Oct, 2017  Peer-reviewed

44. Reduced current collapse in multi-fingered AlGaN/GaN MOS-HEMTs with dual field plate

R. Yamaguchi, Y. Suzuki, J. T. Asubar, H. Tokuda, M. Kuzuhara

2017 IEEE IMFEDK Technical Digest 92 - 93 Aug, 2017

45. Effect of reverse bias annealing on the properties of AlGaN/GaN MIS-HEMTs with recessed-gate structure

W. Gamachi, K. Ishii, J. T. Asubar, H. Tokuda, M. Kuzuhara

2017 IEEE IMFEDK Technical Digest 2017 88 - 89 Jul, 2017eer-reviewed

46. Effective Suppression of Current Collapse in AlGaN/GaN HEMTs

(INVITED)
J. T. Asubar, H. Tokuda, M. Kuzuhara
Proceedings of the Samahang Pisika ng Pilipinas 2017 Jul, 2017  Peer-reviewed  Invited

47. AlGaN/GaN metal-insulator-semiconductor high-electron mobility transistors with high on/off current ratio of over 5 x 10(10) achieved by ozone pretreatment and using ozone oxidant for Al2O3 gate insulator
    Hirokuni Tokuda, Joel T. Asubar, Masaaki Kuzuhara
    JAPANESE JOURNAL OF APPLIED PHYSICS 55(12) 120305-1 - 120305-5 Dec, 2016  Peer-reviewed

48. AlGaN/GaN metal-insulator-semiconductor high-electron mobility transistors with high on/off current ratio of over 5 x 10(10) achieved by ozone pretreatment and using ozone oxidant for Al2O3 gate insulator
    Hirokuni Tokuda, Joel T. Asubar, Masaaki Kuzuhara
    JAPANESE JOURNAL OF APPLIED PHYSICS 55(12) 120305 - (5) Dec, 2016  Peer-reviewed

49. Highly-stable and low-state-density Al2O3/GaN interfaces using epitaxial n-GaN layers grown on free-standing GaN substrates
    Shota Kaneki, Joji Ohira, Shota Toiya, Zenji Yatabe, Joel T. Asubar, Tamotsu Hashizume
    APPLIED PHYSICS LETTERS 109(16) 162104-1 - 162104-9 Oct, 2016  Peer-reviewed

50. Insulated gate and surface passivation structures for GaN-based power transistors

(INVITED)
Zenji Yatabe, Joel T. Asubar, Tamotsu Hashizume
JOURNAL OF PHYSICS D-APPLIED PHYSICS 49(39) 393001-1 - 393001-19 Oct, 2016  Peer-reviewed  Invited

51. Pushing the GaN HEMT towards its theoretical limit

(INVITED)
J. T. Asubar, J. Ng, H. Tokuda, M, Kuzuhara
Compound Semiconductor Magazine 22 26 - 31 Oct, 2016  Peer-reviewed  Invited

52. AlGaN/GaN high-electron-mobility transistor technology for high-voltage and low-on-resistance operation

(INVITED)
Masaaki Kuzuhara, Joel T. Asubar, Hirokuni Tokuda
JAPANESE JOURNAL OF APPLIED PHYSICS 55(7) 070101-1 - 070101-12 Jul, 2016  Peer-reviewed  Invited

53. AlGaN/GaN HEMTs on Free-standing GaN Substrates with Breakdown Voltage of 5 kV and Effective Lateral Critical Field of 1 MV/cm
    J. Ng, J. T. Asubar, H. Tokuda, M, Kuzuhara
    CS MANTECH, Tech Dig. 2016 215 - 218 Jun, 2016  Peer-reviewed

54. Highly reduced current collapse in AlGaN/GaN high-electron-mobility transistors by combined application of oxygen plasma treatment and field plate structures
    Joel T. Asubar, Satoshi Yoshida, Hirokuni Tokuda, Masaaki Kuzuhara
    JAPANESE JOURNAL OF APPLIED PHYSICS 55(4) 04EG07-1 - 04EG07-5 Apr, 2016  Peer-reviewed

55. Large As sublattice distortion in sphalerite ZnSnAs2 thin films revealed by x-ray fluorescence holography
    Kouichi Hayashi, Naotaka Uchitomi, Keitaro Yamagami, Akiko Suzuki, Hayato Yoshizawa, Joel T. Asubar, Naohisa Happo, Shinya Hosokawa
    JOURNAL OF APPLIED PHYSICS 119(12) 125703-1 - 125703-9 Mar, 2016  Peer-reviewed

56. Effect of Metal Electrode Edge Irregularities on Breakdown Voltages of AlGaN/GaN HEMTs

S. Makino, S. Ohi, J. T. Asubar, H. Tokuda, M. Kuzuhara

2016 IEEE IMFEDK Technical Digest 2016 94 - 95 2016

57. Breakdown degradation of AlGaN/GaN HEMTs with multi-finger gate patterns

T. Yamazaki, Y. Suzuki, S. Ohi, J. T. Asubar, H. Tokuda, M. Kuzuhara

2016 IEEE IMFEDK Technical Digest 2016 96 - 97 2016

58. Impact of Drain Electrode Shape Irregularities on Breakdown Voltage of AlGaN/GaN HEMTs
    Shintaro Ohi, Shinya Makino, Taisei Yamazaki, Hirokuni Tokuda, Joel Tacla Asubar, Masaaki Kuzuhara
    2016 COMPOUND SEMICONDUCTOR WEEK (CSW) INCLUDES 28TH INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE & RELATED MATERIALS (IPRM) & 43RD INTERNATIONAL SYMPOSIUM ON COMPOUND SEMICONDUCTORS (ISCS) 2016  Peer-reviewed

59. Impact of oxygen plasma treatment on the dynamic on-resistance of AlGaN/GaN high-electron-mobility transistors
    Joel T. Asubar, Yoshiki Sakaida, Satoshi Yoshida, Zenji Yatabe, Hirokuni Tokuda, Tamotsu Hashizume, Masaaki Kuzuhara
    APPLIED PHYSICS EXPRESS 8(11) 111001-1 - 111001-4 Nov, 2015  Peer-reviewed

60. Current Collapse Reduction in AlGaN/GaN HEMTs by High-Pressure Water Vapor Annealing
    Joel T. Asubar, Yohei Kobayashi, Koji Yoshitsugu, Zenji Yatabe, Hirokuni Tokuda, Masahiro Horita, Yukiharu Uraoka, Tamotsu Hashizume, Masaaki Kuzuhara
    IEEE TRANSACTIONS ON ELECTRON DEVICES 62(8) 2423 - 2428 Aug, 2015  Peer-reviewed

61. Suppressed Current Collapse in High Pressure Water Vapor Annealed AlGaN/GaN HEMTs
    Y. Kobayashi, J. T. Asubar, K. Yoshitsugu, H. Tokuda, M. Horita, Y. Uraoka, M. Kuzuhara
    CS MANTECH, Tech Dig. 2015 185 - 188 May, 2015  Peer-reviewed

62. Correlation between Electroluminescence and Current Collapse in AlGaN/GaN HEMTs
    S. Ohi, Y. Sakaida, J. T. Asubar, H. Tokuda, M. Kuzuhara
    CS MANTECH, Tech Dig. 2015 265 - 268 May, 2015  Peer-reviewed

63. Interface trap states in Al2O3/AlGaN/GaN structure induced by inductively coupled plasma etching of AlGaN surfaces
    Zenji Yatabe, Joel T. Asubar, Taketomo Sato, Tamotsu Hashizume
    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE 212(5) 1075 - 1080 May, 2015  Peer-reviewed

64. Calculating relaxation time distribution function from power spectrum based on inverse integral transformation method
    Zenji Yatabe, Toru Muramatsu, Joel T. Asubar, Seiya Kasai
    PHYSICS LETTERS A 379(7) 738 - 742 Mar, 2015  Peer-reviewed

65. High Drain Current and Low On-Resistance in AlGaN/GaN HEMTs with Au-Plated Ohmic Electrodes

Y. Suzuki, K. Tone, J. T. Asubar, H. Tokuda, M. Kuzuhara

2015 IEEE IMFEDK Technical Digest 2015 52 - 53 2015

66. Current Collapse in AlGaN/GaN HEMTs with a GaN Cap Layer

S. Yoshida, Y. Sakaida, J. T. Asubar, H. Tokuda, M. Kuzuhara

2015 IEEE IMFEDK Technical Digest 2015 48 - 49 201

67. Cu/Al/Mo/Au and Ni/Al/Mo/Au ohmic contacts for AlGaN/GaN heterostructures

A. Sasakura, J. T. Asubar, H. Tokuda, M. Kuzuhara

2015 IEEE IMFEDK Technical Digest 2015 42 - 43 2015

68. Improved Current Collapse in AlGaN/GaN HEMTs with 3-Dimensional Field Plate Structure

A. Suzuki, K. Akira, J. T. Asubar, H. Tokuda, M. Kuzuhara

2015 IEEE IMFEDK Technical Digest 2015 36 - 37 2015

69. High Breakdown Voltage AlGaN/GaN HEMTs on Free-Standing GaN Substrate

J. H. Ng, K. Tone, J. T. Asubar, H. Tokuda, M. Kuzuhara

2015 IEEE IMFEDK Technical Digest 2015 54 - 55 2015

70. Characterization of electronic states at insulator/(Al)GaN interfaces for improved insulated gate and surface passivation structures of GaN-based transistors

(INVITED)
Zenji Yatabe, Yujin Hori, Wan-Cheng Ma, Joel T. Asubar, Masamichi Akazawa, Taketomo Sato, Tamotsu Hashizume
JAPANESE JOURNAL OF APPLIED PHYSICS 53(10) 100213-1 - 100213-10 Oct, 2014  Peer-reviewed

71. Reduced thermal resistance in AlGaN/GaN multi-mesa-channel high electron mobility transistors
    Joel T. Asubar, Zenji Yatabe, Tamotsu Hashizume
    APPLIED PHYSICS LETTERS 105(5) 053510-1 - 053510-5 Aug, 2014  Peer-reviewed

72. Evaluation of off-bias-stress induced surface charging at AlGaN/GaN surface using a dual-gate transistor structure
    Kenya Nishiguchi, Joel T. Asubar, Tamotsu Hashizume
    JAPANESE JOURNAL OF APPLIED PHYSICS 53(7) 070301-1 - 070301-4 Jul, 2014  Peer-reviewed

73. Improved current stability in multi-mesa-channel AlGaN/GaN transistors
    Joel Asubar, Kota Ohi, Kenya Nishiguchi, Tamotsu Hashizume
    PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 11, NO 3-4 11(3-4) 857 - 861 2014  

74. Current Stability in Multi-Mesa-Channel AlGaN/GaN HEMTs

(INVITED)
Kota Ohi, Joel Tacla Asubar, Kenya Nishiguchi, Tamotsu Hashizume
IEEE TRANSACTIONS ON ELECTRON DEVICES 60(10) 2997 - 3004 Oct, 2013  Peer-reviewed  Invited

75. Zinc-blende MnAs thin films directly grown on InP (001) substrates as possible source of spin-polarized current
    Hiroto Oomae, Joel T. Asubar, Shinichi Nakamura, Yoshio Jinbo, Naotaka Uchitomi
    JOURNAL OF CRYSTAL GROWTH 338(1) 129 - 133 Jan, 2012  Peer-reviewed

76. Room-Temperature Ferromagnetism in (Zn, Mn, Sn)As-2 Thin Films Applicable to InP-Based Spintronic Devices
    Naotaka Uchitomi, Hiroto Oomae, Joel T. Asubar, Hironori Endo, Yoshio Jinbo
    JAPANESE JOURNAL OF APPLIED PHYSICS 50(5) 05FB02-1 - 05FB02-5 May, 2011  Peer-reviewed

77. Ferromagnetic ZnSnAs2:Mn chalcopyrite semiconductors for inp-based spintronic
    Naotaka Uchitomi, Joel T. Asubar, Hiroto Oomae, Hironori Endoh, Yoshio Jinbo
    e-Journal of Surface Science and Nanotechnology 9 95 - 102 Mar 12, 2011  Peer-reviewed

78. Three Dimensional Local Structure Analysis of ZnSnAs2:Mn by X-ray Fluorescence Holography
    Kouichi Hayashi, Naotaka Uchitomi, Joel T. Asubar, Naohisa Happo, Wen Hu, Shinya Hosokawa, Motohiro Suzuki
    JAPANESE JOURNAL OF APPLIED PHYSICS 50(1) 01BF05-1 - 01BF05-4 Jan, 2011  Peer-reviewed

79. Anomalous Hall Effect and Magnetoresistance in Mn-Doped ZnSnAs2 Epitaxial Film on InP Substrates
    Hiroto Oomae, Joel T. Asubar, Yoshio Jinbo, Naotaka Uchitomi
    JAPANESE JOURNAL OF APPLIED PHYSICS 50(1) 01BE12-1 - 01BE12-4 Jan, 2011  Peer-reviewed

80. Magnetic properties and surface morphology of MnAs thin films grown by MBE on GaAs(111) substrates
    K. Oomori, J. T. Asubar, T. Ishibashi, Y. Jinbo, N. Uchitomi
    IOP Conference Series: Materials Science and Engineering 21(1) 012024-1 - 012024-5 2011  Peer-reviewed

81. Evidence of pseudomorphic growth of ZnSnAs2 epitaxial layers on nearly lattice matched InP substrates
    H. Endo, J. T. Asubar, Y. Agatsuma, T. Ishibashi, Y. Jinbo, N. Uchitomi
    IOP Conference Series: Materials Science and Engineering 21(1) 012030-1 - 012030-5 2011  Peer-reviewed

82. Dependence of MBE-grown ZnSnAs2:Mn epitaxial film properties on Mn doping level
    H. Oomae, J. T. Asubar, M. Haneta, Y. Agatsuma, T. Ishibashi, Y. Jinbo, N. Uchitomi
    IOP Conference Series: Materials Science and Engineering 21(1) 012026-1 - 012026-5 2011  Peer-reviewed

83. Annealing effects on impurity band conduction of ZnSnAs2 epitaxial films
    Joel T. Asubar, Yuji Agatsuma, Yoshio Jinbo, Takayuki Ishibashi, Naotaka Uchitomi
    IOP Conference Series: Materials Science and Engineering 21(1) 012031-1 - 012031-11 2011  Peer-reviewed

84. Effect of thermal annealing on the properties of narrow-bandgap ZnSnAs(2) epitaxial films on InP(001) substrates
    Yuji Agatsuma, Joel T. Asubar, Yoshio Jinbo, Naotaka Uchitomi
    Physics Procedia 3(2) 1341 - 1344 2010  Peer-reviewed

85. High-Resolution X-ray Diffraction Studies of ZnSnAs2 Epitaxial Films Nearly Lattice-matched to InP Substrates
    Physics Procedia 3(2) 1351 - 1356 2010  Peer-reviewed

86. MBE growth and Low temperature Thermal Annealing of Ferromagnetic Semiconductor (Ga,Mn)As/Zn-doped-GaAsSuperlattice Structures
    H. Nakagawa, J.T. Asubar, Y. Jinbo, N. Uchitomi
    The Institute of Electronics, Information and Communications Engineers of Japan (IEICE) Technical Report Component Parts and Materials (CPM) 107(325) 109 - 113 Nov, 2009

87. Electrical Properties of ZnSnAs2 Thin Films Grown by MBE
    J.T. Asubar, T. Yokoyama, Y. Jinbo, N. Uchitomi
    The Institute of Electronics, Information and Communications Engineers of Japan (IEICE) Technical Report Component Parts and Materials (CPM) 107(325) 103 - 107 Nov, 2009

88. MBE Growth and Characterization of Mn-doped ZnSnAs2 Chalcopyrite Thin Films on Si (001) Substrates
    Y. Agatsuma, J.T. Asubar, Y. Jinbo, N. Uchitomi
    Japan Society of Applied Physics Ternary and Multinary Compounds Professional Group 2008 Conference Report March 2009 149 Mar, 2009

89. Evidence of Impurity Band Conduction in ZnSnAs2 Epitaxial Films
    J.T. Asubar, Y. Jinbo, N. Uchitomi
    Japan Society of Applied Physics Ternary and Multinary Compounds Professional Group 2008 Conference Report March 2009 121 Mar, 2009

90. MBE growth and properties of GeMn thin films on (001) GaAs
    R. Tsuchida, J. T. Asubar, Y. Jinbo, N. Uchitomi
    JOURNAL OF CRYSTAL GROWTH 311(3) 937 - 940 Jan, 2009  Peer-reviewed

91. Low-temperature annealing effects on (Ga,Mn)As/Zn-GaAs superlattice structures grown on GaAs(001) substrates
    J. T. Asubar, H. Nakagawa, Y. Jinbo, N. Uchitomi
    JOURNAL OF CRYSTAL GROWTH 311(3) 933 - 936 Jan, 2009  Peer-reviewed

92. MBE growth of Mn-doped ZnSnAS(2) thin films
    Joel T. Asubar, Yoshio Jinbo, Naotaka Uchitomi
    JOURNAL OF CRYSTAL GROWTH 311(3) 929 - 932 Jan, 2009  Peer-reviewed

93. Impurity band conduction and negative magnetoresistance in p-ZnSnAs 2 thin films
    Joel T. Asubar, Yoshio Jinbo, Naotaka Uchitomi
    Physica Status Solidi (C) Current Topics in Solid State Physics 6(5) 1158 - 1161 2009 

94. FABRICATION AND STRUCTURAL CHARACTERIZATION OF NEARLY LATTICE-MATCHED p-ZnSnAs2/n-InP HETEROJUNCTIONS
    Joel T. Asubar, Shin'ichi Nakamura, Yoshi Jinbo, Naotaka Uchitomi
    2009 IEEE 21ST INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE & RELATED MATERIALS (IPRM) 255 - + 2009  Peer-reviewed

95. Comparison of annealing effects on Zn-doped GaMnAs and undoped GaMnAs epilayers
    H. Nakagawa, J. T. Asubar, Y. Jinbo, N. Uchitomi
    APPLIED SURFACE SCIENCE 254(20) 6648 - 6652 Aug, 2008  Peer-reviewed

96. Electrotransport properties of p-ZnSnAs2 thin films grown by molecular beam epitaxy on semi-insulating (001) InP substrates
    Joel T. Asubar, Ariyuki Kato, Yoshio Jinbo, Naotaka Uchitomi
    JAPANESE JOURNAL OF APPLIED PHYSICS 47(1) 657 - 660 Jan, 2008  Peer-reviewed

97. MBE growth of Mn-doped Zn-Sn-As compounds on (001) InP substrates
    J. T. Asubar, A. Kato, T. Kambayashi, S. Nakamura, Y. Jinbo, N. Uchitomi
    JOURNAL OF CRYSTAL GROWTH 301 656 - 661 Apr, 2007  Peer-reviewed

98. MBE growth and properties of GaMnAs with high level of Zn acceptor incorporation
    J. T. Asubar, S. Sato, Y. Jinbo, N. Uchitomi
    Physica Status Solidi (A) Applications and Materials Science 203(11) 2778 - 2782 Sep, 2006  Peer-reviewed

99. Effect of Low temperature Thermal Annealing on the Properties of Zn-doped Ferromagnetic Semiconductor (Ga,Mn)As
    H. Nakagawa, J.T. Asubar, Y. Jinbo, N. Uchitomi
    Japan Society of Applied Physics Ternary and Multinary Compounds Professional Group 2006 Conference Report 29 March, 2006

100. Structural Investigation of Mn-doped ZnSnAs2 Thin Films Grown by MBE on InP (001) Substrates
     J.T. Asubar, A. Kato, S. Nakamura, Y. Jinbo, N. Uchitomi
     Japan Society of Applied Physics Ternary and Multinary Compounds Professional Group 2006 Conference Report March 2006 33 Mar, 2006

101. Zn Incorporation and Its Effect on the Properties of GaMnAs Ferromagnetic Semiconductors Grown by Molecular Beam Epitaxy
     J.T. Asubar, S. Sato, Y. Jinbo, N. Uchitomi
     Japan Society of Applied Physics Ternary and Multinary Compounds Professional Group 2005 Conference Report 185 Feb, 2005