Evidence of reduced interface states in Al₂O₃/AlGaN MIS structures via insertion of ex situ regrown AlGaN layer

We report on the impact of the 3 nm thick ex situ AlGaN regrown layer prior to insulator deposition on the interfacial properties of Al₂O₃/AlGaN/GaN metal-insulator-semiconductor (MIS) structures. MIS-capacitors (MIScaps) with regrown AlGaN layer exhibited anomalously excessive threshold voltage shift compared to reference sample without regrown AlGaN, suggesting highly reduced interface states density (D _it). Moreover, MIScaps with regrown AlGaN layer exhibited “spill-over” in the capacitance-voltage profiles, further evidencing the improved Al₂O₃/AlGaN interfaces. Fabricated three-terminal MIS-HEMTs with regrown AlGaN showed less hysteresis in transfer curves, enhanced maximum drain current, and increased linearity over the reference device.