Structural, optical and electrical properties of sol–gel prepared Ga:ZnO thin film

Abstract

Transparent conductive gallium-doped zinc oxide films (GZO) with different thickness were grown on a glass substrate by cost effective sol–gel spin coating technique using zinc acetate and gallium nitrate as precursors for Zn and Ga ions, respectively. The structural, optical and electrical properties of the films were analysed as a function of film thickness using X-ray diffraction (XRD), spectrophotometry and Hall effect measurements. X-ray diffraction analysis showed the polycrystalline nature of the films with a hexagonal (wurtzite) crystal structure and a preferred orientation with c-axis, perpendicular to the substrate. Experimental results revealed that within a certain range of thickness, the grain size along with the root mean square (RMS) surface roughness increase with film thickness. The strain relaxation was found to be maximum for the thicker film. The average optical transmittance of all the films was over 86% and a sharp fundamental absorption edge with a slight red shifting was observed in the visible region. A lowest resistivity 3.66 × 10(3 Ω cm and highest carrier concentration were achieved for GZO film of thickness 396 nm. The result obtained from this study showed that the structural, optical and electrical properties of GZO films deposited by sol–gel method were strongly affected by the film thickness.