900 V/1.6 Normally Off MOSFET on

In this paper, we report the device performance of a high-voltage normally off Al₂O₃/GaN MOSFET on the Si substrate. Normally off operation is obtained by multiple cycles of O₂ plasma oxidation and wet oxide-removal gate recess process. The recessed normally off GaN MOSFET with 3 μm gate-drain distance exhibits a maximum drain current of 585 mA/mm at 9 V gate bias. The threshold voltage of the MOSFET is 2.8 V with a standard derivation of 0.2 V on the sample with an area of 2 × 2 cm². The gate leakage current is below 10^-6 mA/mm during the whole gate swing up to 9 V and the ION/IOFF ratio is larger than 109, indicating the good quality of Al₂O₃ gate insulator. The MOSFET with 10 μm gate-drain distance shows a three terminal OFF-state breakdown voltage (BV) of 967 V at zero gate-source bias with a drain leakage current criterion of 1 μA/mm. The specific ON-resistance (R_ON,SP) of the device is 1.6 mQ · cm² and the power figure of merit (BV²/R_ON,SP) is 584 MW/cm².