Impact of current measurement on switching characterization of GaN transistors

Gallium nitride (GaN) power devices promise better performance and efficiency compared to silicon transistors. How-ever, the switching characterization of GaN devices is challenging, because of the high switching speed. In this paper the switching behavior of a GaN transistor is investigated with special focus on the impact of current measurement. A circuit simulation model including the critical parasitic elements was built to analyze parasitic effects and their impact on the switching transients. To confirm the simulation results by experiments, a PCB board was designed and different current measurement methods are compared. It is shown that the current sensor adds additional inductance in the power loop and causes ringing and oscillations. Furthermore, it can be seen, that the current sensor resistance damps the oscillations and improves the switching transients. Therefor, both variables should be small in order to reproduce the real switching characteristics as accurate as possible.