Minimum gate trigger current degradation in 4.5 kV 4H-SiC commutated gate turn-off thyristor

The increment in minimum gate trigger current in a 4H-SiC commutated gate turn-off thyristor after the current stress test is investigated. The recombination at the intersection line of the Shockley-type stacking faults and the pn junction causes a reduction in the level of carrier injection from the anode to the gate. The,current gain of the top pnp bipolar junction transistor, therefore, decreases, and the minimum gate trigger current increases. The,minimum gate trigger current after the current stress test does not return to that before the current stress test at 200 degrees C, although the on-state voltage of the degraded thyristor returns to that of the original one when the temperature is increased to more than 150 degrees C. The Shockley-type stacking faults, which are parallel to the current flow from the anode to the gate and cause the increment in minimum gate trigger current, exist even if the temperature increases. (C) 2014 The Japan Society of Applied Physics