Characterization of Gallium-Doped ZnO Thin Films Deposited by the Ultrasonic Spray Pyrolysis Technique

Abstract

Production and study of ZnO thin films have attracted the attention of scientists and semiconductor industries due to their favorable properties. In this research work, the properties of pure and gallium-doped (Ga-doped) ZnO thin films were investigated. All films were deposited at 450°C, from zinc acetate and gallium pentanedionate as precursors, by the ultrasonic spray pyrolysis technique. The Ga content varied from 1 to 5 at% in the ZnO thin films. The structural, optical, electrical, and morphological properties of pure and Ga-doped ZnO thin films were analyzed. The preferential orientation of (002) was observed for both doped and undoped ZnO thin films. The crystallite size for all samples is almost similar in all samples. However, the two-theta value is slightly shifted to a higher value when Ga is added to the ZnO thin films. From FESEM images, the geometrical-shaped grains, uniformly distributed in the films, were observed. The smooth surface (i.e., average roughness less than 20 nm), dense film and well-connected grains are seen in AFM analysis. The optical transmission spectra revealed that the transmittance of light from the samples is decreased as the Ga content increased. The bandgap of samples increases with the Ga content in ZnO thin film. The n-type conductivity, electron mobilities, and carrier concentrations were obtained from Hall effect measurements. It was observed that carrier concentration for Ga-doped ZnO films is increased with the Ga content in the films. The results obtained can provide an idea for optimizing the best deposition conditions as well as improving the material properties, which could be useful in various areas.