Low-loss SiC trench metal-oxide-semiconductor field-effect transistor with improved switching speed and excellent reverse recovery

Abstract A SiC trench metal-oxide-semiconductor field-effect transistor (MOSFET) that combines a sidewall control gate, a source-tied bottom split gate (SG), and a source-trench heterojunction (SBH-MOS) is proposed. Compared with the control gate of a conventional double-trench MOSFET (CON-MOS), that of the proposed MOSFET is etched further to markedly narrow its width, and a source-connected SG is placed beneath it. These modifications substantially reduce direct gate-drain coupling, thereby lowering the gate-drain and input capacitances. In the source trench, an N + /P − polysilicon junction forms a heterojunction with the SiC. During reverse conduction, this heterojunction suppresses hole injection, so reverse current is carried predominantly by electrons and the reverse-recovery current is strongly reduced. The objective is to reduce switching loss, shorten the switching interval, and improve gate-oxide reliability. Simulation results show 87.7% and 60% declines in the gate-drain and input capacitances, respectively, without lowering the breakdown voltage. The reverse conduction voltage decreases by 33.9% and the peak reverse-recovery current reduces by 88.1%. The switching speed improves by 32%, the switching energy decreases by 63.2%, and the gate-oxide electric field is reduced. These gains incur a 10.2% reduction in the Baliga figure of merit and a 96.1% decline in the high-frequency figure of merit. Overall, SBH-MOS delivers faster, lower-energy switching than CON-MOS without compromising blocking capability. Thus, it is a promising candidate for high-frequency, high-efficiency power conversion.