10 kV SiC BJTs — Static, switching and reliability characteristics

Abstract

Open-base breakdown voltages as high as 10.5 kV (91% of theoretical avalanche limit and 125 V/μm), on-resistance of 110 mΩ-cm2 close to the unipolar limit of 94 mΩ-cm2, and current gain as high as 75 are measured on 10 kV-class SiC BJTs. Monolithic Darlington-connected BJTs fabricated on the same wafer yield current gains as high as 3400, and show Si BJT-like output characteristics with a differential on-resistance as low as 44 mΩ-cm2 in the saturation region and a distinct quasi-saturation region. Switching measurements performed at a DC link voltage of 5 kV and collector current of 8 A feature a collector current rise time as low as 30 ns during turn-on and collector voltage recovery time as low as 100 ns during turn-off. Very low turn-on and turn-off switching energies of 4.2 mJ and 1.6 mJ, respectively, are extracted from the switching transients, which are 19 and 25 times smaller than the corresponding switching energies reported on 6.5 kV Si IGBTs. When turnedon to a short-circuited load at a collector bias of 4500 V, the 10 kV BJT shows a temperature-invariant, withstand time in excess of 20 μs. Leakage currents <; 1μA (system limit) are measured, even after 234 hours of operation under a DC collector bias of 5000 V at elevated temperatures.