A Revised Growth Model for Transparent Conducting Ga Doped ZnO Films: Improving Crystallinity by Means of Buffer Layers

Ga-doped ZnO (GZO) thin films are recently raising both scientific and industrial interests, due to the lack of natural resources. Indium is a crucial raw material, due to ITO modern touchscreen market. By doping ZnO with Ga conductive transparent thin films with various concentrations of dopant are prepared by DC magnetron sputtering from ceramic targets. It is shown how the Ga content plays an important role on the growth kinetics on an initial stage of the film formation and hence on the morphologies, microstructure and electrical properties of as-grown GZO films. A mechanism explaining the role of Ga content on the nucleation process and the structure of growing films is proposed. Based on this mechanism, it is successfully demonstrated that the crystalline quality and hence the conductivity of GZO thin films can be improved by using a GZO buffer layer.