Hard-Switched Overvoltage Robustness of p-Gate GaN HEMTs at Increasing Temperatures

An essential ruggedness characteristic of power devices is the capability to withstand the transient overvoltage in power electronic applications. As the newly commercialized GaN HEMTs can switch faster, and under higher voltage biases, it is important to identify their true overvoltage limitations in transient switching events. For the first time, this work characterizes the transient overvoltage capability and failure mechanisms of GaN HEMTs under hard-switched turn-off conditions at increasing temperatures, by using a clamped inductive switching circuit with a variable parasitic inductance. This test method allows a flexible control over both the magnitude and the dV/dt of the transient overvoltage. The overvoltage robustness of two commercial enhancement-mode (E-mode) p-gate HEMTs was extensively studied: one with the Ohmic-type gate and the other with the Schottky-type gate. The overvoltage failure of the two devices was found to be determined by the overvoltage magnitude rather than the dV/dt. Tests were repeated at increasing temperatures (100 °C and 150 °C), and the failures of both devices were consistent with room temperature results. The two types of devices show different failure behaviors and the underlying mechanisms have been revealed by physics-based device simulations.