Effects of oxygen partial pressure on doping properties of Ga-doped ZnO films prepared by ion-plating with traveling substrate

Polycrystalline Ga-doped ZnO (GZO) thin films were prepared by ion-plating on a traveling glass substrate at 200 °C. Effects of O2 gas flow rate and Ga2O3 content in source on the electrical and structural properties of GZO films were investigated. GZO films having a low resistivity of 210− 4 Ω cm order were obtained under the conditions of Ga2O3 contents of 3–5 wt.% and O2 gas flow rates below 10 sccm. In particular, for GZO films prepared with a Ga2O3 content of 4 wt.% at an O2 gas flow rate of 2.5 sccm, the lowest resistivity of 2.23 × 10− 4 Ω cm was obtained; the carrier concentration and Hall mobility were 1.17 × 1021 cm− 3 and 23.9 cm2/Vs, respectively. Excess Ga2O3 content in source (> 6 wt.%) cause deterioration both in crystallinity and in electric property most probably due to the solubility limit for Ga doping in ZnO at the glass substrate temperature of 200 °C. Excess O2 gas flow rates (> 10 sccm) during the film growth also lower the electric properties of the GZO films.