Investigation of the γ-irradiation-induced degradation mechanism of p-channel p-GaN/u-GaN/AlGaN MESFETs

In this letter, a Schottky-gated p-GaN/u-GaN/AlGaN p-channel metal–semiconductor field-effect transistor on a SiC substrate with high irradiation tolerance is demonstrated, and the irradiation-induced degradation mechanism is also revealed. The devices exhibit a slight degradation in the saturation drain current and a negative shift of threshold voltage. Meanwhile, the fabricated devices exhibit outstanding stability, even after ten-consecutive dual-sweep, dual-sweep with various scan ranges, and long-time stress measurements. However, an increase in hysteresis and the occurrence of a knee point in dual-sweep transfer characteristics have been observed. The trap distributions under the gate after irradiation, extracted using the frequency-dependent conductance method, show that the trap state density increases from 5.68–9.05 × 1012 to 0.72–2.35 × 1013 cm−2 eV−1, accompanied by a shift in trap energy from 0.32–0.35 to 0.33–0.43 eV. The introduction of deep-level and high-density traps captures a large number of holes, leading to current degradation, increased hysteresis, and knee point.