We demonstrate a novel surface passivation process for AlGaN/GaN heterostructures utilizing an ultrathin Al2O3 layer (~1 nm). The Al deposition and thermal annealing processes in UHV were found to form the ultrathin Al2O3 layer on the surface of the AlGaN/GaN heterostructure, which was confirmed by in-situ X-ray photoelectron spectroscopy (XPS) analysis. The reverse leakage current for the Schottky gate contact on the Al2O3-passivated heterostructure surface was reduced by three orders of magnitude compared to that for the conventional Schottky gate structure. C-V results showed good gate controllability of the two-dimensional electron gas (2DEG) by the novel gate structure.
Published in physica status solidi (a), 2001, Wiiley-VCH Verlag GmbH & Co. KGaA, Weinheim