Al2O3 Insulated-Gate Structure for AlGaN/GaN Heterostructure Field Effect Transistors Having Thin AlGaN Barrier Layers

An Al 2 O 3 insulated-gate (IG) structure was utilized for controlling the surface potential and suppressing the gate leakage in Al 0.2 Ga 0.8 N/GaN heterostructure field effect transistors (HFETs) having thin AlGaN barrier layers (less than 10 nm). In comparison with the Schottky-gate devices, the Al 2 O 3 IG device showed successful gate control of drain current up to V GS = +4 V without leakage problems. The threshold voltage in the Al 2 O 3 IG HFET was about -0.3 V, resulting in the quasi-normally-off mode operation.