Development of transparent conductive Mg and Ga co-doped ZnO thin films: Effect of Mg concentration

Transparent conductive Mg and Ga co-doped ZnO (MGZO) thin films were prepared on glass substrates by RF magnetron sputtering technique. The effect of Mg concentration from 0 to 15at% on the structural, chemical, morphological, optical and electrical properties of MGZO thin films was investigated. X-ray diffraction studies showed that the pure ZnO, Mg-doped ZnO (MZO) and MGZO thin films were grown as a polycrystalline hexagonal wurtzite phase without secondary phase. The 2θ angle position of the (0002) peak of the MZO and MGZO thin films was shifted towards a higher angle with increasing Mg concentration. A typical survey XPS spectrum of the MGZO thin films confirmed the presence of Mg, Ga, Zn and O in the MGZO films. The MGZO thin films had a smoother surface morphology than those of ZnO and MZO. The MGZO thin film deposited at Mg concentration of 5at% showed the widest optical band gap energy of 3.75eV and the lowest electrical resistivity of 6.89×10^-4Ωcm. However, the electrical and optical characteristics of the MGZO thin films deposited over 5 at% Mg concentration were deteriorated with increasing Mg concentration.