An Analytical Model for Predicting Turn-ON Overshoot in Normally-OFF GaN HEMTs

Recently, a major challenge in the adoption of wide bandgap semiconductors for power electronic applications is the need to trade device performance for device safety. In this article, methods for predicting gate voltage overshoot in normally-OFF gallium nitride (GAN) high electron mobility transistors (HEMTs) are derived in order to deliver optimal device performance. Two models are proposed; a simple, yet less accurate second order model and a complex, yet more accurate fourth order model. These models allow for the calculation of gate resistances necessary for a desired amount of gate voltage overshoot. The nonlinear capacitances of the device are considered in the analysis. The models are validated with an experimental double-pulse tester. These newly developed models allow design engineers to extract the best possible performance of commercially available GaN devices while keeping the devices in their safe-operating region.