Comparative study of AlGaN/GaN metal–oxide–semiconductor heterostructure field-effect transistors with Al2O3 and HfO2 gate oxide

AlGaN/GaN metal–oxide–semiconductor heterostructure field-effect transistors (MOSHFETs) with Al2O3 gate oxide which was deposited by atomic layer deposition (ALD) were fabricated and their performance was then compared with that of AlGaN/GaN MOSHFETs with HfO2 gate oxide. The capacitance (C)–voltage (V) curve of the Al2O3/GaN MOS diodes showed a lower hysteresis and lower interface state density than the C–V curve of the HfO2/GaN diodes, indicating better quality of the Al2O3/GaN interface. The saturation of drain current in the ID–VGS relation of the Al2O3 AlGaN/GaN MOSHFETs was not as pronounced as that of the HfO2 AlGaN/GaN MOSHFETs. The gate leakage current of the Al2O3 MOSHFET was five to eight orders of magnitude smaller than that of the HfO2 MOSHFETs.

► The performance of Al2O3/AlGaN/GaN MOSHFETs and HfO2/AlGaN/GaN MOSHFETs was compared.
► The fabrication process was identical except the gate oxide deposited by ALD.
► The interface quality was better in Al2O3/AlGaN/GaN MOSHFETs than in HfO2/AlGaN/GaN MOSHFETs.
► The gate leakage current was five to eight orders of magnitude smaller in the Al2O3 MOSHFETs.