Turn-ON of High-Voltage SiC Thyristors for Fast-Switching Applications

This paper is focused on the characterization of the turn-ON transition of high-voltage SiC thyristors of different epi-layer thicknesses and active-area sizes to determine their suitability and limitations in high-d I/dt, fast-switching applications. The unique aspects of this paper 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-cm(2) thyristors; 10-kV, 1.05-cm(2) thyristors; and 15-kV, 1.05-cm(2) thyristors, all fabricated by Cree, Inc. (now Wolfspeed) for the U.S. Army Research Laboratory. The highest dI/dt and the current density were 13 kA/ms and 3.2 kA/cm(2) for a parallel pair of 0.5-cm(2) thyristors, with pulsed current peaking 250 ns from initial gate trigger. All devices evaluated were capable of switching a current pulse >2 kA/cm(2) within a period of less than 2 mu s. These evaluations have broad application in helping to inform SiC device design tradeoffs for increasing epi thickness, increasing device area, and the effects of lifetime enhancement processes. Results are also presented for initial exploration of fast-switching applications for these devices.