Experimental Evaluation and Analysis of Switching Transient's Effect on Dynamic ON-Resistance in GaN HEMTs

The dynamic ON-resistance in gallium nitride (GaN) devices is problematic as it can impair the converter's efficiency due to the increased conduction loss. In this paper, the hard-switching transient's effect on the dynamic ON-resistance is, for the first time, evaluated experimentally on a commercial high-voltage GaN high electron mobility transistor. A new R-dyn-(ds),on measurement circuit with fast sensing speed is designed, and an accurate measurement of R-dyn-(ds),on can be realized experimentally within 49.6 ns after the device's current reaches to the load current. A double-pulse-test setup is designed to comprehensively evaluate the switching transient's effect on R-dyn-(ds),on under different operating conditions. From the experimental results, it is found that the turn ON and turn-OFF gate resistance have a significant impact on the dynamic ON-resistance whereas the cross-talk effect on R-dyn-(ds),on is negligible. Specifically, at 400 V/25 A, more than 27% (28.2%) increase in R-dyn-(ds),on is observed when the external turn-ON (turn-OFF) gate resistance increases from 0 to 20 Omega. Detailed discussion and quantitative analysis are provided to explain the experimental results. In terms of the turn-ON process, it is concluded that the R-dyn-(ds),on variation is mainly caused by the different numbers of generated hot electrons. For the turn-OFF transient, it is confirmed the variation of drain current at different dv/dt slew rate leads to the R-dyn-(ds),on difference.