Novel power MOSFET with drain-side N–Si/N-SiGe heterojunctions for improving reverse recovery performance

—A novel power MOSFET structure with Drain-side N–Si/N-SiGe Heterojunctions (DH-MOS) is proposed by introducing a N SiGe region which is sandwiched between the N-drift region and N+ substrate on the drain side. The operation mechanism and simulation verification of DH-MOS are presented. Due to the difference in valence band of N Si/N SiGe heterojunction, holes can be more easily expelled from the N-drift region into N SiGe region during the reverse conduction of DH-MOS, resulting in a significant reduction in hole density inside the N-drift region, thus improving the reverse recovery performance. Simulation results show that the reverse recovery charge (Qrr) of DH-MOS is 2.08 μC/cm², approximately 66.34 % lower than the 6.18 μC/cm² of conventional MOS. The introduction of new DH-MOS structure with N–Si/N-SiGe heterojunctions does not result in a significant increase in reverse conduction voltage (VF). In addition, it does not sacrifice any forward conduction and blocking characteristics. The proposed DH-MOS introduces changes on the drain side, unlike existing methods which focus on the source side or drift region. And it can be compatible with existing improving measures to further improve the reverse recovery performance.