Low temperature epitaxial growth and characterization of Ga-doped ZnO thin films on Al ₂ O ₃ (0 0 0 1) substrates prepared with different buffer layers

This article reports the epitaxial growth and characterization of 1 wt% Ga-doped ZnO (GZO) thin films prepared without buffer layer and with three different buffer layers of ZnO, GaN and MgO on Al ₂ O ₃ (0 0 0 1) substrates by RF magnetron sputtering at a growth temperature of 250 °C. X-ray diffraction and transmission electron microscopy studies showed that the GZO thin films deposited on the GaN- and ZnO-buffered substrates were grown epitaxially. However, the GZO thin films deposited on the non- and MgO-buffered substrates had a polycrystalline hexagonal wurtzite phase with a highly c-axis preferred out-of-plane and a random in-plane orientation. Electrical studies of the GZO thin film deposited on the non-buffered substrate showed the lowest resistivity of 6.8 × 10 ^-3 Ω cm as compared to these deposited on three buffered substrates. The crystallinity, microstructure, morphological, optical and electrical properties of the GZO thin films were influenced by the nature of the three investigated buffered layers.