Study of the turn-on of various high-voltage SiC thyristors

This research is focused on characterization of the turn-on transition of high voltage SiC thyristors of different epilayer thicknesses and active area sizes to determine their suitability and limitations in high-dI/dt, fast-switching applications. The unique aspects of this study include the very high current density being switched through the thyristors over a short period of time at initial turn-on, resulting in very high instantaneous dissipated power over the small device volume. The devices that were characterized were 6 kV, 0.5 cm2 super gate turn-off thyristors (SGTOs), 10 kV, 1.05 cm2 SGTOs, and 15 kV, 1.05 cm2 SGTOs, all fabricated by Cree, Inc. for the Army Research Laboratory. The highest dI/dt and current density were 13 kA/microsecond and 3.2 kA/cm2 for a parallel pair of 0.5 cm2 thyristors, with pulse current peaking 250 ns from initial gate trigger. These evaluations help determine tradeoffs between series-stacking two lower-voltage thyristors versus using a single thicker-epi device, or paralleling two small-area devices versus switching one larger device, for fast-switching applications.