Microstructure, optical and photoluminescence properties of Ga-doped ZnO films prepared by pulsed laser deposition

Ga-doped zinc oxide (GZO) films were prepared on Si(1 0 0) and fused silica substrates by pulsed laser deposition (PLD). The influence of gallium doping on the morphology, microstructure, optical and photoluminescence properties of GZO films were investigated by scanning electron microscopy, atomic force microscopy, X-ray diffraction, UV-visible spectrophotometer and photoluminescence spectra. It was found that the Ga doping concentration altered the microstructure and crystallite size of GZO films. X-ray diffraction study revealed that the undoped ZnO and GZO films exhibited a preferred orientation along the (0 0 2) plane and the Ga atoms doped into ZnO film deteriorated the film crystallinity. The Ga doping resulted in the decrease of surface roughness and crystallite size of GZO films, the increase in transmittance in the visible region and the increase of optical energy gap of the GZO films. The room-temperature photoluminescence spectra demonstrated that the films exhibited near-band-edge (NBE) emission, while deep-level (DL) emission was also observed in the GZO films deposited at Ga concentrations over 2 at%. The intensity ratio of NBE-to-DL emission in the PL spectra of the GZO films was strongly dependent on the Ga concentrations.