Physical properties of Ga-doped ZnO thin films by spray pyrolysis

In this work, we report the structural, optical and electrical properties of the transparent conducting GZO thin films prepared by spray pyrolysis method. We sought optimum deposition conditions yielding GZO films with desired physical properties, specifically good crystalline quality microstructure, low resistivity and high transparency. The electrical conductivity and mobilities of GZO thin films are very good as compared with previous reported spray pyrolysed films. Gallium doped zinc oxide (GZO) thin films were prepared using the simple, flexible and cost-effective spray pyrolysis technique. The physical properties of the films were studied as a function of increasing gallium dopant concentration from 1 to 9 at.%. The films were characterized by various methods to understand their structural, morphological, optical and electrical properties. The X-ray diffraction analysis revealed that the films were polycrystalline in nature having a hexagonal wurtzite type crystal structure with a preferred grain orientation in the (0 0 2) direction. Scanning electron microscopy (SEM) measurements reveal that the surface morphology of the films changes continuously with a decrease in the grain size due to Ga doping. All the films showed nearly 90% of transparency in the entire visible region. A blue shift of the optical band gap was observed with an increase in Ga doping. Room temperature photoluminescence (PL) measurement of the deposited films indicates incorporation of Ga in ZnO lattice. At 3 at.% Ga doping, the film has lowest resistivity of 6.8 × 10 −3 cm while the carrier concentration is highest.