6.5 kV ultra soft & fast recovery diode (U-SFD) with high reverse recovery capability

This paper presents a 65 kV ultra soft and fast recovery diode (U-SFD) for a high power IGBT module. The U-SFD has shallow p type Schottky junctions and deep pn junctions. A high blocking voltage of 6.8 kV even at -40°C and a low forward voltage drop (V_F) Of 4.6 V at 125°C, which show a positive thermal coefficient, are obtained. The Schottky junctions are effective even for 6.5 kV diodes in achieving better trade-off relationships between V_F and the reverse recovery loss, V_F and the reverse recovery peak current, and V_F and the reverse recovery current change compared to a conventional pn diode. Moreover, the U-SFD with a HiRC (high reverse recovery capability) structure demonstrates good switching durability at a high dc-link voltage of 4.4 kV and at 125°C