Effect of a ZnO buffer layer on the properties of Ga-doped ZnO thin films grown on Al2O3 (0 0 0 1) substrates at a low growth temperature of 250 °C

4 wt% Ga-doped ZnO (GZO) thin films have been prepared on the buffered and non-buffered Al2O3 (0 0 0 1) substrates by RF magnetron sputtering technique at a low growth temperature (250 °C). The effect of a ZnO buffer layer on the crystallinity, optical, and electrical properties of the GZO thin films is investigated. X-ray diffraction and transmission electron microscopy studies showed that the GZO thin film on a buffered substrate was epitaxially grown at a low growth temperature of 250 °C with an orientation relationship of (0001)[112¯0]GZO||(0001)[112¯0]Al2O3. However, the GZO thin film on a non-buffered substrate was grown as a polycrystalline hexagonal wurtzite phase with c-axis preferred, out-of-plane orientation, and random in-plane orientation. The optical transmittance in the visible region and the electrical resistivity of the GZO thin film was improved by introducing a ZnO buffer layer from 70% to 80% and from 4.69×10−3 to 1.01×10−3 Ω cm, respectively.