Browsing by Author "Sasaki, Kohei"

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    10-kV Ga2O3 Charge-Balance Schottky Rectifier Operational at 200 ◦C
    Qin, Yuan; Xiao, Ming; Porter, Matthew; Ma, Yunwei; Spencer, Joseph; Du, Zhonghao; Jacobs, Alan G.; Sasaki, Kohei; Wang, Han; Tadjer, Marko; Zhang, Yuhao (IEEE, 2023-08)
    This work demonstrates a lateral Ga2O3 Schottky barrier diode (SBD) with a breakdown voltage (BV) over 10 kV, the highest BV reported in Ga2O3 devices to date. The 10 kV SBD shows good thermal stability up to 200◦C, which is among the highest operational temperatures reported in multi-kilovolt Ga2O3 devices. The key device design for achieving such high BV is a reduced surface field (RESURF) structure based on the p-type nickel oxide (NiO), which balances the depletion charges in the n-Ga2O3 channel at high voltage. At BV, the chargebalanced Ga2O3 SBD shows an average lateral electric field (E-field) over 4.7 MV/cm at 25 ◦C and over 3.5 MV/cm at 200◦C, both of which exceed the critical E-field of GaN and SiC. The 10 kV SBD shows a specific on-resistance of 0.27 ·cm2 and a turn-on voltage of 1 V; at 200◦C, the former doubles and the latter reduces to 0.7 V. These results suggest the good potential of Ga2O3 devices for mediumand high-voltage, high-temperature power applications.
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    2 kV, 0.7 mΩ·cm2 Vertical Ga2O3 Superjunction Schottky Rectifier with Dynamic Robustness
    Qin, Yuan; Porter, Matthew; Xiao, Ming; Du, Zhonghao; Zhang, Hongming; Ma, Yunwei; Spencer, Joseph; Wang, Boyan; Song, Qihao; Sasaki, Kohei; Lin, Chia-Hung; Kravchenko, Ivan; Briggs, Dayrl P.; Hensley, Dale K.; Tadjer, Marko; Wang, Han; Zhang, Yuhao (IEEE, 2023)
    We report the first experimental demonstration of a vertical superjunction device in ultra-wide bandgap (UWBG) Ga2O3. The device features 1.8 μm wide, 2×1017 cm-3 doped n-Ga2O3 pillars wrapped by the charge-balanced p-type nickel oxide (NiO). The sidewall NiO is sputtered through a novel self-align process. Benefitted from the high doping in Ga2O3, the superjunction Schottky barrier diode (SJ-SBD) achieves a ultra-low specific on-resistance (RON,SP) of 0.7 mΩ·cm2 with a low turn-on voltage of 1 V and high breakdown voltage (BV) of 2000 V. The RON,SP~BV trade-off is among the best in all WBG and UWBG power SBDs. The device also shows good thermal stability with BV > 1.8 kV at 175 oC. In the unclamped inductive switching tests, the device shows a dynamic BV of 2.2 kV and no degradation under 1.7 kV repetitive switching, verifying the fast acceptor depletion in NiO under dynamic switching. Such high-temperature and switching robustness are reported for the first time in a heterogeneous superjunction. These results show the great potential of UWBG superjunction power devices.
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    Recent progress of Ga2O3 power technology: large-area devices, packaging and applications
    Qin, Yuan; Wang, Zhengpeng; Sasaki, Kohei; Ye, Jiandong; Zhang, Yuhao (IOP Publishing, 2023-06)
    Benefitted from progress on the large-diameter Ga2O3 wafers and Ga2O3 processing techniques, the Ga2O3 power device technology has witnessed fast advances toward power electronics applications. Recently, reports on large-area (ampere-class) Ga2O3 power devices have emerged globally, and the scope of these works have gone well beyond the bare-die device demonstration into the device packaging, circuit testing, and ruggedness evaluation. These results have placed Ga2O3 in a unique position as the only ultra-wide bandgap semiconductor reaching these indispensable milestones for power device development. This paper presents a timely review on the state-of-the-art of the ampere-class Ga2O3 power devices (current up to >100 A and voltage up to >2000 V), including their static electrical performance, switching characteristics, packaging and thermal management, and the overcurrent/overvoltage ruggedness and reliability. Exciting research opportunities and critical technological gaps are also discussed.