An Accurate Analytical Switching Transient Model for GaN HEMT Operating at Cryogenic Temperature

Gallium Nitride High Electron Mobility Transistors (GaN HEMTs) exhibit faster switching speed and lower on resistance compared to silicon-based devices. GaN HEMTs are also regarded as one of the most promising candidates for cryogenic power electronics due to their unique characteristics. This paper establishes a comprehensive switching transient model for GaN HEMTs at cryogenic temperatures. First, the proposed device level model features high model accuracy by considering the temperature-dependent transfer characteristics and output characteristics in both backward and forward directions, and parasitic capacitances with respect to their applied voltages. Furthermore, the crosstalk phenomenon that can affect the conduction of GaN HEMT in reverse active region are also included. Then, the switching transient process in the circuit level is modelled. The proposed model is compared with existing models, demonstrating its high accuracy with relative errors below 5 %. Experimental waveforms for the turn-on and turn-off transients of a commercial 650 V GaN HEMT are measured at 143 K, 203 K, and room temperature. The proposed model exhibits good agreement with the experimental results with maximum relative errors of turn-on loss within 6 %, turn-off loss within 9%, turn-on time within 7 % and turn-off time within 10 %. The results indicate that the turn-on speed of GaN HEMTs significantly increases and switching loss decreases at cryogenic temperatures. The proposed model provides a theoretical analysis of the mechanisms behind these changes in switching transients and can be of great use in loss prediction of GaN HEMTs under cryogenic conditions.