AlGaN/GaN High Electron Mobility Transistor degradation under on- and off-state stress

AlGaN/GaN High Electron Mobility Transistors (HEMTs) with various gate lengths have been step-stressed under both on- and off-state conditions. On-state, high power stress tests were performed on 0.17 μm gate length HEMTs and a single 5 μm spaced TLM pattern. Significant degradation of the submicron HEMTs as compared to the excellent stability of the TLM patterns under the same stress conditions reveal that the Schottky contact is the source of degradation. Off-state stress showed a linear relationship between the critical degradation voltage and gate length, though two dimensional ATLAS/Blaze simulations show that the maximum electric field is similar for all gate lengths. Additionally, as the drain bias was increased, the critical voltage decreased. However, the cumulative bias between the gate and drain remained constant, further indicating that the electric field is the main mechanism for degradation.