Gate leakage reduction of AlGaN/GaN MOS-HFETs with HfO2 prepared by ALD

The gate leakage reduction about four to seven orders of magnitude for HfO₂ MOSHFETs (~10^-10A/mm at -15V) prepared by Atomic Layer Deposition (ALD) technique at 350°C with and without oxygen-plasma treatment in comparison to HFET, was observed. A lower hysteresis evaluated from c-V curves of MOSHFET with oxygen-plasma treatment (OPT) after annealing (500°C for 15 min in N₂) was found. The C-V curve for MOSHFET without OPT exhibited an increase of capacitance at negative voltages which corresponds with hypothesis of the interfacial layer formation at the oxide/GaN interface. And also, the high density of oxide interface states affects adversely the interface quality, like as the C-V hysteresis, leakage current, hot electron phenomena, etc.