Optimization of SiC UMOSFET Structure for Improvement of Breakdown Voltage and ON-Resistance

This paper proposes an optimized structure of 4H-SiC U-shaped accumulation-mode MOSFET (U-ACCUFET), which exhibits lower on-resistance and higher breakdown voltage. In this structure, an n-doped region is added underneath the gate trench, which covers the p+shielding region. The new appended section spreads out the electrons to the bottom of the p+shielding region and conducts the electrons in the downward direction. Output on-state characteristic curves (IDS-VDS), on-resistance, transfer characteristic curves (IDS-VGS), threshold voltage (Vt), subthreshold slope, and off-state characteristics of the optimized structure are observed. The proposed device shows on-resistance of 1.55 mQ · cm2at VGS= 16 V and VDS= 1 V and breakdown voltage of 2624 V at VGS= 0 V. The simulation results indicate a superior performance of the optimized U-ACCUFET structure as the on-resistance reduces by 6% and breakdown voltage increases by 7.2% as compared with that of the conventional one. Also, the figure of merit VBR2/RONis improved by 21.6%.