Normally-off hybrid Al2O3/GaN MOSFET on silicon substrate based on wet-etching

This paper reports a normally-off high voltage hybrid Al₂O₃/GaN gate-recessed MOSFET fabricated on silicon substrate. The normally off operation was implemented by digital gate recess using an oxidation and wet etching based AlGaN barrier remove technique. The Al₂O₃/GaN MOSFET features a true normally off operation with a threshold voltage of 2 V extracted by the linear extrapolation of the transfer curve. The three terminal off-state breakdown voltage is 1650 V for the device with 30 μm gate-drain distance with floating Si substrate. The breakdown voltage is limited to 1000 V when the Si substrate is grounded. The on-resistance is 7.0 mΩ·cm² for the device with 30 μm gate-drain distance and the power figure of merit is 388 MW/cm². The small signal RF performance of the normally-off GaN MOSFET is also evaluated.