Abstract
We report the first study of current collapse in ultra-wide bandgap high-Al AlGaN channel heterostructure field-effect transistors (HFETs) using short-pulse biasing. Our results show that, under applied pulsed gate and drain voltages, the current collapse results from increased resistance of the source- gate and gate-drain regions but not from the channel under the gate. We also show that passivation of access regions of the high-Al channel HFET with SiNx results in significant reduction in current collapse.