Effect of Ga doping concentrations, substrate temperatures and working pressures on the electrical and optical properties of ZnO thin films

Abstract

We fabricated Ga-doped ZnO (GZO) thin films on glass substrate by RF magnetron sputtering method with different conditions of Ga2O3 concentration, substrate temperature and working pressure. Next we investigated the electrical, optical and structural properties of the GZO thin films. At a substrate temperature of 300 °C, a working pressure of 1 mTorr, and a Ga2O3 concentration of 3 wt%, the GZO thin films showed the lowest resistivity of 3.16 × 10−4 Ω cm, a carrier concentration of 7.64 × 1020 cm−3 and a Hall mobility of 25.8 cm2/Vs. Moreover, the GZO thin films exhibited the highest (002) orientation under the same conditions and the full width at half maximum of X-ray peak was 0.34°. All GZO thin films showed the optical transmittance of more than 80 % in the visible range regardless of working conditions. The Burstein–Moss effect was observed by the change of doping concentration of Ga2O3. The GZO thin films were fabricated to have the good electrical and optical properties through optimizing doping concentration of Ga2O3, substrate temperature, working pressure. Therefore, we confirmed the possibility of application of GZO thin film as transparent conductive oxide used in flat panel display and solar cell.