Characteristic Variations Between Commercial GaN HEMTs at Cryogenic Temperatures Down to 4K

GaN HEMTs are great candidates for low temperature power electronics; however, they have not been extensively studied at cryogenic temperatures down to 4K. This paper aims to study the variations between commercial GaN HEMT characteristics such as static on-resistance (RON), drain-source leakage, and reverse gate leakage. The device being tested is the GaN Systems GS66508T which is a high-power Schottky contact HEMT capable of 650 V and 30 A. The static RON testing reveals that it decreases by 85% from room temperature (RT) down to 4K. The variability between devices is seen to be 1–3 mΩ over this temperature range. The difference in RON at RT is found to be 7% of the maximum, and at 4K it is found to be 15% of the maximum. The drain leakage is seen to increase exponentially with drain voltage, with the highest drain leakage measured at RT of 0.26 µA. The drain leakage quickly decreases with temperature, with almost no leakage at 4K. This trend is similar for all devices revealing that the GaN HEMTs may be able to handle higher drain voltages at low temperatures than what is specified on the datasheet. Further testing is required to confirm this. The reverse gate leakage also increases with drain voltage and decreases with temperature with the maximum gate leakage measured at room temperature of 21.8 nA.