Experimental analysis and modeling of GaN normally-off HFETs with trapping effects

A 70 mΩ / 600 V normally-off AlGaN/GaN HFET is analyzed and modeled. In particular, static and dynamic characteristics are investigated with the focus on modeling trapping effects and their influence on the on-state resistance and on the switching characteristic. Two methods to measure these trapping effects are compared, a clamped measurement of the on-state resistance and a measurement of a shift in the transfer characteristic. Both methods are suitable to extract time constants of trapping effects, which are required for the trap model. A comparison of the measurements demonstrates the link between the increased dynamic on-state resistance and the threshold voltage shift. The developed model is suitable to simulate the performance of the HFET during switching and conduction intervals.