The GaN trench gate MOSFET with floating islands

A novel GaN trench gate (TG) MOSFET with P-type floating islands (FLI) in the drift region, which can suppress the electric field peak at the bottom of the gate trench during the blocking state and prevent premature breakdown in the gate oxide, is proposed and investigated by TCAD simulations. The influence of the thickness, position, doping concentration and length of the FLI on the breakdown voltage (BV) and specific on-resistance (Ron, sp) is studied, providing useful guidelines for the design of this new type of device. Using optimized parameters for the FLI, the GaN FLI TG-MOSFET reaches a BV as high as 2464V with a Ron, sp of 3.0 mΩ+ cm2. Compared to the conventional GaN TG-MOSFET with the same structure parameters, the Baliga figure of merit (BFOM) is enhanced by 150%, getting closer to the theoretical limit for GaN devices.