Abrupt conversion of the conductivity and band-gap in the sputter grown Ga-doped ZnO films by a change in growth ambient: Effects of oxygen partial pressure

Abstract

GZO films were sputter grown under the different O2/Ar + O2 ratios and the systematic investigation has been tried in an effort to get a better understanding on the correlations between the involved defects and the film properties. The abrupt conversion of the resistivity was observed from the highly conductive, 2.52 ⅹ10−4 Ω cm, at pure Ar ambient to resistive, 0.295 Ω cm, with an oxygen addition of 1% in the ambient, accompanying the significant reduction in the electron density and mobility. Hall measurement at 10 K–300 K and in-depth XPS analysis suggested that the higher Hall mobility and carrier density in the film grown in pure Ar ambient may be due to a lower compensation ratio and the compensation via Gazn-Vzn complexes may play a major role in the sudden reduction in the electron density and the reduced density of the Gazn, substitutional donors induced by oxygen addition in growth ambient.