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 (I-DS-V-DS), on-resistance, transfer characteristic curves (I-DS-V-GS), threshold voltage (V-t), subthresholdslope, and off-state characteristics of the optimized structure are observed. The proposed device shows on-resistance of 1.55 m Omega . cm(2) at V-GS = 16 V and V-DS = 1 V and breakdown voltage of 2624 V at V-GS = 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 V-BR(2)/R-ON is improved by 21.6%.