High-Temperature PBTI in Trench-Gate Vertical GaN Power MOSFETs: Role of Border and Semiconductor Traps

For the first time we investigate the positive threshold voltage instability in GaN-based trench gate MOSFETs in the high-temperature regime (150-240 degrees C). First, by inverse Laplace transform we determine the equivalent distribution of activation energies of the traps responsible for PBTI, with a peak at 0.75 eV from the conduction band of GaN. Second, we demonstrate that the recovery transients have a non-monotonic trend. This result, never described before, is attributed to the interplay between electron de-trapping from border traps, and hole de-trapping from defects in the p- type body layer, located 0.65 eV above the valence band energy of GaN, and preliminary ascribed to gallium vacancies in the semiconductor. Results provide relevant insight for optimizing the high-temperature stability of GaN vertical FETs.