Gate Bias Dependence of Defect-Mediated Hot-Carrier Degradation in GaN HEMTs

Monte Carlo analysis of hot-electron degradation in AlGaN/GaN high-electron mobility transistors shows that, for gate voltages corresponding to semi-ON bias conditions, the average electron energy has a spatial peak with (E_AVE) ~ 1.5 eV. The peak is located at the edge of the gate. At this location, the carrier versus energy distribution has a large tail extending over 3 eV. When transferred to the lattice, this energy can cause defect dehydrogenation and device degradation. These results are consistent with the experimental data indicating maximum degradation in the semi-ON bias condition.