Gallium Nitride (GaN) HEMTs demonstrate superior performance at cryogenic temperatures, making them promising candidates for lunar missions where temperatures vary from 50 to 400 K. However, the current collapse effect increases dynamic on-state resistance (Rdson) during switching, leading to additional energy loss, especially in high-frequency applications. To conduct a comprehensive study, we developed an automated characterization platform for dynamic Rdson extraction over numerous conditions. The design considerations include 1) programmable temperatures, voltages, currents, etc., 2) electrothermal-mechanical compatibility with the cryocooler across a wide temperature range, and 3) software framework for full automation. Preliminary results for a specific device show that dynamic Rdson varies non-monotonically with temperature increment, as it increases at 50 – 180 K and then decreases at 180 – 400 K. Dynamic Rdson follows this trend at both hard- and soft-switching, but is more sensitive to stressors at hard switching, while remaining nearly unchanged during soft switching.
