Investigation of transparent and conductive undoped Zn2In2O5−x films deposited on n-type GaN layers

Transparent, conductive, multicomponent oxide films composed of undoped Zn2In2O5−x were deposited on n-type GaN layer using rf sputtering. We investigated the dependence of the surface, electrical, and optical properties on the sputtering parameters, including rf power, total pressure, and the post-deposition annealing process. We obtained high transparency (>80% in the visible and near-infrared ranges) and low electrical resistivity (2.58×10−4 Ω cm). Atomic force microscopy and optical transmittance measurements of Zn2In2O5−x films were used to investigate the mechanisms of resistivity variation in the films. The ohmic performances of Zn2In2O5−x contacts to the n-type GaN layer are also demonstrated.