High voltage degradation of GaN high electron mobility transistors with AlGaN back barrier on SiC substrate

We have stressed GaN High Electron Mobility Transistors (HEMTs) with AlGaN back barrier on SiC substrate at high voltages at normal and high temperatures. A pattern of device degradation differs from what occurred in reported GaN-on-SiC HEMTs and GaN-on-Si HEMTs. The recoverable degradation of drain current is observed under Vds=0 step stress condition, but no degradation is observed under off-state condition. We attribute the results to electron injection into the back quantum well, other than electron trapping. Raman scattering indicates planar strain is greatly enhanced under Vds=0V condition, which is likely to assist electron in tunneling the back barrier.