Investigation of transparent and conductive undoped Zn ₂In ₂O _5-x films deposited on n-type GaN layers

Transparent, conductive, multicomponent oxide films composed of undoped Zn ₂In ₂O _5-x were deposited on n-type GaN layer using rf sputtering. We investigated the dependence of the surface, electrical, optical properties on the sputtering parameters, including rf power, total pressure, 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 cm). Atomic force microscopy and optical transmittance measurements of Zn ₂In ₂O _5-x films were used to investigate the mechanisms of resistivity variation in the films. The ohmic performances of Zn ₂In ₂O _5-x contacts to the n-type GaN layer are also demonstrated.