Is the GaN HEMT More Prone to Sustained Oscillations under Cryogenic Conditions?

Low temperature power electronics is critical in many different applications, such as all-electric aircraft and deep space probes. Wide bandgap (WBG) devices are becoming increasingly popular due to their high performance over traditional silicon (Si) technology. However, their low parasitic capacitance and fast switching speed make them more susceptible to switching oscillations. Various modeling approaches and suppression methods for gallium nitride (GaN) high-electron mobility transistor's (HEMT's) oscillations have been proposed. However, there is a lack of research on GaN HEMT's oscillations under cryogenic conditions. In this article, the cryogenic static characterization of a 650 V enhancement-mode GaN HEMT is reported using a liquid helium experimental platform. Based on the experimental reverse transconductance, the instability analysis of GaN HEMT is conducted by using the small-signal circuit model. The calculation results show that the voltage range of the GaN sustained oscillation is wider at low temperature. Finally, the results are verified by simulation, indicating that GaN HEMTs are more likely to experience sustained oscillation due to the increase of reverse transconductance and decrease of loop resistance at low temperature, which should be carefully considered during the design phase for low temperature applications.