The GaN trench MOSFET with adaptive voltage tolerance achieved through a dual-shielding structure

Abstract

A novel GaN trench gate vertical MOSFET (PSGT-MOSFET) with a double-shield structure composed of a separated gate (SG) and a p-type shielding layer (P_shield) is proposed and investigated. The p-type shielding layer (P_shield) is positioned within the drift region, which can suppress the electric field peak at the bottom of the trench during the off state. This helps to prevent premature breakdown of the gate oxide layer. Additionally, the presence of P_shield enables the device to have adaptive voltage withstand characteristics. The separated gate (SG) can convert a portion of gate to- -drain capacitance (Cgd) into drain-to-source capacitance (Cds), significantly reducing the gate-to-drain charge of the device. This improvement in charge distribution helps enhance the switching characteristics of the device. Later, the impact of the position and length of the p-type shielding layer (P_shield) on the breakdown voltage (BV) and specific on-resistance (Ron_sp) was studied. The influence of the position and length of the separated gate (SG) on gate charge (Qgd) and breakdown voltage was also investigated. Through TCAD simulations, the parameters of P_shield and SG were optimized. Compared to conventional GaN TG-MOSFET with the same structural parameters, the gate charge was reduced by 88%. In addition, this paper also discusses the principle of adaptive voltage withstand in PSGT-MOSFET.