Yasumichi Yasuda

A novel soft and fast recovery diode (SFD) with thin p-layer formed by Al-Si electrode

A novel, soft and fast recovery diode (SFD) is presented which has extremely thin p-layers formed by an Al-Si electrode and deep p/sup +/-layers. By using the thin p-layer, the hole density in the n/sup -/-layer close to the p-n junction is reduced, and a 1/2.5 lower recovery current peak, 1/3 lower recovery current change, and 1.5 times faster recovery time are realized compared to a conventional p-n diode. Moreover, increasing the barrier height of the p-layer causes the leakage current and forward voltage drop to decrease. It is also demonstrated that electrical noise and turn-on loss of an IGBT module in an inverter circuit can be significantly improved by using the SFD as a free wheeling diode.<<ETX>>

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/spl deg/C and a low forward voltage drop (V/sub F/) Of 4.6 V at 125/spl deg/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/sub F/ and the reverse recovery loss, V/sub F/ and the reverse recovery peak current, and V/sub 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/spl deg/C.