Fig. 1. (Color online) The cross-section schematic of the AlGaN/GaN HEMT.

Fig. 2. (Color online) Reverse I–V characteristics measured from 298 to 458 K in a step of 40 K of (a) unannealed HEMT, (b) annealed HEMT.

Fig. 3. (Color online) (a) The gate capacitance versus V_G characteristics of both HEMTs. (b) The electric fields across AlGaN as the function of V_G for both HEMTs.

Fig. 4. (Color online) The ln (J/E) versus E^0.5 and the linear fit for the slope and intercepts of (a) unannealed HEMT, (b) annealed HEMT. Inset: the B(T) versus for the extraction of the height of the trap state.

Fig. 5. (Color online) Gate leakage measured during the reverse gate-bias step stress of (a) unannealed HEMT, (b) annealed HEMT. Inset: absolute value of reverse gate-bias step stress versus times (V_step = –5 V, t_step = 60 s).

Fig. 6. (Color online) Gate leakage current before and after reverse bias step stress of (a) unannealed HEMT, (b) annealed HEMT, (c) maximum output currents, and (d) transfer characteristics before and after reverse bias step stress of the unannealed HEMT.

Fig. 7. (Color online) Schematic of the gate leakage at reverse gate bias before the stress of (a) unannealed HEMT, (b) annealed HEMT.