A Novel 4H–SiC/Si Heterojunction IGBT Achieving Low Turn–Off Loss

Abstract

In this paper, a novel silicon carbide (SiC) insulated gate bipolar transistor (IGBT) with a 4H–SiC/Si heterojunction in the buffer layer (HBL) is proposed to improve the turn–off characteristic. Compared with the conventional 4H–SiC IGBT, the polysilicon region is integrated in the buffer layer to form a natural potential well, which can help to store excess carriers in the turn–off process. The simulation results indicate that the turn–off time (toff) was reduced from 325 ns to 232 ns, and the turn–off loss (Eoff) was decreased from 2.619 mJ to 1.375 mJ, while a similar on–state ability was maintained. This means that reductions of 28.6% in toff and 47.5% in Eoff were achieved. The Eoff of the two devices at different forward voltages (VF) was compared by changing the carrier lifetime. As a result, a better trade–off between Eoff and VF was also achieved by the proposed HBL–IGBT. Moreover, the heterojunction of the HBL–IGBT can be formed with the plasma–activated direct bonding technology, which is compatible with the conventional fabrication process.