High-Frequency Switching Properties and Low Oxide Electric Field and Energy Loss in a Reverse-Channel 4H-SiC UMOSFET

Abstract

A reverse-channel 4H-SiC trench gate metal-oxide-semiconductor field-effect transistor (UMOSFET) (RC-MOS) is proposed in this article. The RC-MOS is demonstrated to have low specific ON-resistance ( $R_{\mathrm{ON,sp}}$ ) by numerical simulation. The trench oxide in the RC-MOS is fully protected by the n+ source, the p-shield, and the p-base regions. Thus, a reduced trench corner field far below 3 MV/cm can be achieved in both the OFF- and ON-state. Furthermore, the gate-to-drain charge ( ${Q}_{{\text {GD}}}$ ) of the RC-MOS is 33 nC/cm2, which is much lower than that of the dual buffer layer MOSFET (DB-MOS), owing to little overlap between the gate and drain electrodes. Consequently, the RC-MOS exhibits the superior figures of merit ${Q}_{{\text {GD}}} \times {R}_{{{\,\,\text {ON,SP}}}} = {82} \,\,\text {m}\Omega \cdot $ nC. Due to the low reverse transfer capacitance and gate charges in the RC-MOS, the total switching loss of $570~\mu \text{J}$ /cm2 is decreased by 64.5% in comparison to that of the DB-MOS. These superior properties show that the proposed UMOSFET can be a good candidate for further improvements in the gate oxide reliability and high-frequency performance of SiC MOSFETs.