Temperature and thickness-dependent growth behaviour and opto-electronic properties of Ga-doped ZnO films prepared by aerosol-assisted chemical vapour deposition

Abstract

Ga-doped ZnO thin films were deposited onto glass substrates by aerosol-assisted chemical vapour deposition of zinc and gallium acetylacetonates in methanol. The effect of deposition temperature and thickness on the film growth behaviour and functional properties was investigated. It is found that the film's preferred deposition and growth sites on the glass surface change with the substrate temperature. The resulting ZnO:Ga coatings are mainly composed of c-axis oriented crystallites and this (002) texture tends to be weakened by increasing thickness, although their crystallinity exhibits a continuous improvement associated with the emergence of columnar grain structures. The increase of deposition temperature transforms the wedge-shaped film morphology into round-shaped particles and enhances the specimen charge carrier density from 1.263–2.790 × 1020 cm−3 to 4.095–5.282 × 1020 cm−3. Due to the improved carrier mobility with system crystallinity, the film resistivity reduces with thickness and the minimum value obtained is 6.51 × 10−3 Ω cm. High visible transmittance (≈70–90% at 550 nm) and favourable infrared reflection (up to 45.5% at 2500 nm) are also observed in these ZnO:Ga coatings, arising from their wide band gaps and high carrier densities, as well as carrier numbers.