The critical charge density of 4H-SiC thyristors

The critical charge density which determines the maximum voltage ramp (dV/dt) of a thyristor, the minimum value of the gate control current, and the parameters of current filamentation has been determined in SiC thyristors both theoretically and experimentally. For 4H-SiC thyristors blocking 300 to 400 V, the critical charge density has been found to be 2/spl times/10/sup 15/ cm/sup -3/ and 10/sup 14/ cm/sup -3/ at a forward voltage of 5 and 100 V, respectively for an operating temperature of 560 K. The critical current density j/sub 0/ below which the turn-on state is localized has also been estimated theoretically and experimentally. While theoretical calculations predict its value to be 2/spl times/10/sup 2/ A/cm/sup 2/, experimental results show a range of 3/spl times/10/sup 2/ to 7.6/spl times/10/sup 2/ A/cm/sup 2/.