Magnetron sputtering growth and characterization of high quality single crystal Ga-doped n-ZnO thin films

Ga-doped n-type ZnO (ZnO:Ga) films were grown on sapphire substrates by rf magnetron sputtering and their structural, electrical and optical properties were characterized in detail. It was observed that high quality single crystal ZnO:Ga films are obtained, containing up to 1 wt% of Ga. The ZnO:Ga (1 wt%) films grown at 700 °C in pure O2 showed sharp and intense photoluminescence (PL) and high resolution x-ray diffraction (XRD) peaks, with full-width-at-half-maximum values of 150 meV (room temperature PL), 24 meV (12 K PL) and 380 arcsec (XRD), which is slightly better than or comparable with corresponding values from the previously reported ZnO:Ga films. Electrical properties of ZnO:Ga films significantly improved after the rapid thermal processing, resulting in 2.6 × 1019 cm−3 free electron density and 47 cm2 V−1 s−1 mobility after annealing at 900 °C in the case of 1 wt% film. The intensity of the PL peaks was also enhanced by the heat treatment.