Effect of chlorine on the conductivity of ZnO:Ga thin films

Abstract

An extensive study of the effect of various technological factors on the electrical properties of ZnO thin films obtained by DC magnetron sputtering of ZnO:Ga:Cl ceramic targets on glass substrates has been carried out. The effect of deposition temperature, film thickness, growth rate, background pressure, working gas pressure, preliminary slow-growing and undoped layers, stoichiometric deviation, and Ga and Cl concentrations has been studied. Changes in the growth rate, transparency in the ultraviolet and visible spectral ranges, morphology, crystallinity, and crystallite size have also been analyzed. It has been shown that the effect of co-doping with Cl is most significant at the lowest temperatures, which can decrease the resistivity of the films by 2 times at a deposition temperature of 100 °C. Zinc oxide thin films with a resistivity of 2.5 × 10-4 Ω⋅cm and a figure of merit of 31 kΩ-1 have been successfully obtained. A theoretical model taking into account various types of mobile gallium chlorides has been proposed to elucidate the advantage of co-doping with Cl.