A new Method for Dynamic Ron Extraction of GaN Power HEMTs

Degradation of the dynamic on-state resistance RON of GaN High-Electron-Mobility Transistors (HEMTs) is commonly observed under switching conditions with high drain current, high blocking voltage and high switching frequency. In order to determine this on-state resistance, specific measurement methods need to be developed. Since the drain source voltage of the device changes between hundreds of volts in the off-state and a few mill-volts in the on-state, an accurate determination of the on-state voltage VDSON is not achievable with standard measurement equipment due to the saturation of the DSO's input channel. In this paper, a voltage clamping circuit used to extract the dynamic on-state resistance RON of GaN HEMTs is presented. This method is based on a high-voltage, fast-switching zero recovery SiC Schottky diode. The circuit allows an accurate measurement of RON from 100 ns after turn-on to any arbitrary time and is feasible for operation at high switching frequencies up to 1MHz. Experimentally, the dynamic on-state resistance of 600V normally-off GaN HEMTs is investigated applying this method.