High transmittance–low resistivity ZnO:Ga films by laser ablation

Abstract

High transmittance, low resistivity, and c-axis highly oriented ZnO:Ga thin films on glass were obtained by laser ablation at different deposition temperatures. The surface morphology, crystalline structure, and optical and electrical properties were found to depend directly on substrate temperature. From optical and electrical analyses we observed that the optical transmittance, carrier concentration, and optical energy gap of the ZnO:Ga transparent conductive oxides increased when the deposition temperature is raised from 150 to 300 °C. Films grown on 300 °C substrates showed a low resistivity value of 3.6×10−4 Ω cm, a carrier concentration of 8.7×1020 cm−3, a band gap of 3.81 eV, and a visible transmission of 85%. These films were deposited with an excimer (KrF) laser beam of λ=248 nm operated under optimized conditions of 2.7 mJ/cm2 energy density and 30 Hz repetition rate.