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
$v_{ds}$
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
$v_{ds}$
and
$i_{d}$
, the GaN HEMT successfully turns off the 550 A objective current.