Impacts of conduction band offset and border traps on Vth instability of gate recessed normally-off GaN MIS-HEMTs

An investigation of threshold voltage instability in gate recessed normally-off GaN metal insulator semiconductor high electron mobility transistors (MIS-HEMTs) was performed by analyzing the interface states, border traps, and conduction band offset. To reduce the threshold voltage instability with improved dielectric-GaN interface, plasma enhanced atomic layer deposition (PEALD) technique was successfully employed for very thin SiNx (5nm) as an interfacial layer. Forward biased gate leakage current, capacitance-voltage measurements, and current-transient analysis were performed to find the reason for this improvement. Finally, we proposed an importance of border traps and the conduction band offset which is related to trapping mechanism in transfer characteristics.