By using temperature-dependent current–voltage, variable-frequency capacitance–voltage, and Hall measurements,the effects of the thermal oxidation on the electrical properties of Ni/Au Schottky contacts on lattice-matched In0.18Al0.82N/GaN heterostructures are investigated. Decrease of the reverse leakage current down to six orders of magnitude is observed after the thermal oxidation of the In0.18Al0.82N/GaN heterostructures at 700oC. It is confirmed that the reverse leakage current is dominated by the Frenkel–Poole emission, and the main origin of the leakage current is the emission of electrons from a trap state near the metal/semiconductor interface into a continuum of electronic states associated with the conductive dislocations in the InxAl1-xN barrier. It is believed that the thermal oxidation results in the formation of a thin oxide layer on the InxAl1-xN surface, which increases the electron emission barrier height.
