On the origin of dynamic R_on in commercial GaN-on-Si HEMTs

There are huge differences in dynamic on-resistance R_on, also known as current-collapse, between current GaN power HEMT technologies. Here we illustrate this fact with dynamic R_on measurements on two commercially available devices from 2 different manufacturers, with one showing more than a factor of 2 increase in dynamic R_on after OFF-state drain bias (type 1) and the other one <15% change. HTRB stress for 1000h and 3000h on type 1 and type 2 respectively was found to only make subtle changes to dynamic R_on, with type 1 still showing a much larger dynamic R_on than type 2. A model for dynamic R_on is presented based on a floating, highly resistive, epitaxial buffer whose potential is determined by parasitic leakage paths. The difficulty in controlling local leakage paths can explain the problems that manufacturers are still finding in suppressing dynamic R_on.