Mechanism of Superior Suppression Effect on Gate Current Leakage in Ultrathin Al2O3/Si3N4 Bilayer-Based AlGaN/GaN Insulated Gate Heterostructure Field-Effect Transistors

On the basis of the thin barrier surface (TSB) model, the mechanism of gate current leakage under reverse gate–source bias in nitride-based heterostructure field effect transistors (HFETs) and metal–insulator–semiconductor (MIS) HFETs with an ultrathin (1 nm/0.5 nm) Al 2 O 3 /Si 3 N 4 bilayer has been investigated. The simulations show that the electron tunneling through the Schottky barrier is the dominant mechanism for gate current in conventional HFETs due to the high density of donor like defects on the surface. An Al 2 O 3 /Si 3 N 4 bilayer insulator can substantially reduce the donor like surface defect density and then significantly suppress the gate current leakage in nitrides-base MIS-HFET devices.