Simulation Study of 4H-SiC UMOSFET Structure With p+-polySi/SiC Shielded Region

In this paper, we propose an enhanced efficiency 4H-SiC U-shaped trench-gate MOSFET (UMOSFET) structure. The proposed device structure takes an advantage of a p+-polySi/SiC shielded region to reduce the on-state specific resistance. We show that the heterojunction diode formed by the p+-polySi and the n-drift regions improves the body diode effect, and thereby, reduces the reverse recovery charge. Further, we illustrate through simulation results that in comparison with the traditional p+-SiC shielded UMOSFET, the proposed device structure provides a 56.5% improvement in the figure of merit (including the breakdown voltage and on-resistance), and a 35.7% and 55.5% reduction in specific on-resistance and reverse recovery charge, respectively.

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