Overcurrent Test for GaN HEMT with Cryogenic Cooling

Cryogenic power electronics can significantly improve the converter power density and efficiency. For the transportation applications, cryogenically cooled superconducting machine and cable are adopted to achieve high efficiency performance. If the power electronics circuit can also be designed with cryogenic environment, the overall system performance can be further improved with reduced cost and weight. In this article, the dynamic cryogenic performances of a commercial 650 V gallium nitride (GaN) high electron mobility transistors (HEMT) device are presented. The cryogenic power electronics structure is discussed first. Then, comparisons of room temperature and cryogenic temperature operations are made to illustrate the dynamic switching differences. With the aid of cryogenic cooling, the excessive heat generated by the device can be extracted and junction temperature is lower than room temperature to enable pushing more current flows through the device. The overcurrent test demonstrates that the device is saturated at 250 A under cryogenic temperature, which is much greater than the room temperature value (160 A). Operating mechanisms and explanations are given for the overcurrent test results.