High Current Turn-off of GaN HEMT for Solid-state Circuit Breaker at Cryogenic Temperatures

Gallium Nitride (GaN) high electron mobility transistors (HEMTs) are superior for cryogenically cooled solid-state circuit breakers (SSCBs) in future aircraft applications owing to their low on-resistance and high saturation current. However, during the high current turn-off, it is found that potential voltage and current ringing could happen to damage the device. In this paper, the turn-off failure mechanism of 650V/150A GaN bare dies are analyzed, which could be due to the instability of paralleled switching cells in one GaN bare die. A solution is proposed to use an RC snubber to reduce the overlap of nu(ds) and i(d) in the turn-off process to avoid the unstable region where the hard-switching trajectory goes through. Experiments are conducted to verify the effectiveness of the proposed solution. With the reduced overlap between vds and id, the GaN HEMT successfully turns off the 550 A objective current.