Investigation of SiC trench MOSFET with floating islands

The silicon carbide trench metal-oxide-semiconductor field-effect transistors (SiC UMOSFET) with P+ floating island (FLI) which shields the gate oxide at the bottom of the gate trench from the high electric field during the blocking state and enhances the breakdown voltage (BV), is presented in this study using two-dimensional simulations. The effects of doping concentration, length and position of FLI on BV, electric field distribution and specific on-resistance (R-on,R-sp) are studied, thereby providing particularly useful guidelines for the design of this new type of device when considering the breakdown of the gate oxide layer. For the suitable device design, the results indicate that BV and Baliga figure of merit are, respectively, increased by 150 and 439% compared with a conventional SiC UMOSFET. At the same time, the SiC FLI UMOSFET has smaller gate-drain capacitance and better switching performance compared with the conventional UMOSFET on the condition of the same drift layer parameters. FLI introduced have almost no influence on the recovery characteristics of body diode.