Gallium nitride (GaN) high electron mobility transistors (HEMTs) have shown strong potential for emerging applications such as space exploration, where operating temperatures can fluctuate significantly—from cryogenic to high temperatures. Understanding device behavior under such conditions is essential; however, thermal cycling tests across this wide temperature range remain largely unexplored. In this work, commercial GaN HEMTs were subjected to passive thermal cycling between 50 K and 400 K, with key device parameter shifts monitored throughout the stress cycles. The results revealed negligible gradual degradation, with devices instead exhibiting abrupt failure—a behavior not commonly reported in prior GaN thermal cycling studies. Furthermore, as part of the ongoing effort to understand the failure mechanism, supplementary tests were performed.
