Trap behavior in AlGaN/GaN HEMTs by post-gate-annealing

Trapping effects are investigated to examine the post-gate annealing effects on AlGaN/GaN high-mobility electron transistors (HEMTs) using pulsed I-V and transient measurements. In the unannealed devices, shallow traps are identified, which have an activation of 38 meV at a drain bias of 7 V. The time constant of these traps is determined to be -0.5 μs. Devices annealed at 400 °C for 10 minutes have a significantly smaller number of traps. However, a small number of traps with a longer time constant of 9.2 μs are created or activated during post-gate annealing. 20-minute annealing at 400 °C leads to the increase of the number of traps with emission time constants of 21.6 μs and 1.25 ms. The breakdown voltage improvement by post-gate annealing is attributed to the removal or significant reduction of the shallow level traps.