Reliability of power devices: Bias-induced threshold voltage instability and dielectric breakdown in GaN MIS-HEMTs

This paper reviews the most relevant threshold-voltage instabilities and dielectric breakdown mechanisms in GaN-based transistors with metal-insulator-semiconductor gate. Metal-insulator-semiconductor (MIS) high electron mobility transistors (HEMTs) with partially-recessed gate have been submitted to pulsed and constant voltage stress, with the aim of evaluating the impact of charge trapping processes and dielectric breakdown on device performance and reliability. Three different dielectrics were considered for this investigation: SiN deposited by rapid thermal chemical vapour deposition (RTCVD), SiN deposited by plasma enhanced atomic layer deposition (PE-ALD), and Al2O3 deposited by atomic layer deposition (ALD). The role of bias and temperature is extensively investigated and discussed. The results obtained within this paper are critically compared to previous literature reports, to provide a more complete view of the state-of-the-art.