Background GaN high electron mobility transistors for extreme-environment applications face limited adoption due to complex material physics and reliability concerns.

Purpose This work presents a comprehensive characterization framework spanning a wide temperature range (2–350 K), high vacuum, and high electric field conditions to systematically probe two-dimensional electron gas (2DEG) transport in GaN/AlGaN heterostructures and extract relevant electrical parameters.

Methods Using DC and pulsed measurements, we obtain temperature-dependent I_ds-V_ds output and transfer characteristics and extract key metrics such as threshold voltage and saturation current.

Results The results show that the threshold voltage (V_th) and maximum transconductance (G_mmax) vary with temperature in a nonmonotonic manner, with a pronounced inflection near 180–240 K. Under deep-cryogenic conditions, the derivative of the transfer curve exhibits a double transconductance-peak structure; as V_ds increases, one peak shifts toward more positive gate bias while the other moves toward more negative bias. For the same device, the hard breakdown voltage is approximately 170 V at room temperature, whereas at 200 K the current begins to rise near 92 V and hard breakdown occurs at 117 V.

Conclusions By comprehensively characterizing GaN HEMT DC behavior across a wide temperature range, this study provides quantitative data and a methodological basis for performance optimization, identification of trap-related mechanisms, and device/process optimization for low-temperature applications.