Demonstration of a 700 volt asymmetrical, 4H-SiC gate-turn-off thyristor (GTO)

The potential of SiC-based power switching devices has been well recognized due to its superior materials properties relative to silicon. These properties (which include approximately 10/spl times/ higher breakdown voltage, 3/spl times/ higher band gap, 3/spl times/ higher thermal conductivity and 2/spl times/ higher electron saturated velocity) have the potential to yield significant size, weight and cost reductions as well as efficiency improvements at the systems level for commercial/military power utility and motor control applications. We report here progress on asymmetrical GTOs fabricated in 4H-SiC. The asymmetrical structure is easier to turn-off and has improved breakdown voltage capability compared to the symmetrical structure. The devices fabricated in this study have forward blocking voltage of 700 V in air even though the structures did not have any advanced edge termination. A forward voltage drop of 4.8 V was measured at 350/spl deg/C for a current density of 500 A/cm/sup 2/. Four GTO cells were combined to switch 1.4 amps. Storage times at turn-off were measured to be <100 ns at a current density of 500 A/cm/sup 2/, corresponding to a turn-off current gain of 1. In addition, 8 devices were combined in a package yielding 5 amps, indicating that current hogging is not a problem in these devices.