First principle calculations and opto-electric enhancement in laser ablated GZO thin films

Abstract

Optical and electrical properties of Ga-doped Zinc Oxide (GZO) has been studied in the present article. Density functional theory and Hubbard U (DFT + Ud + Up) based first principle calculations were employed for theoretical estimation whereas Laser ablation method has been used to fabricate GZO thin films on p-GaN, Al2O3 and p-Si substrate for experimental analysis. Single crystal growth of GZO thin films with (002) preferred crystallographic orientation has been shown in X-ray diffraction graphs. The elemental composition of all samples has been studied via EDS (energy dispersive X-ray) spectroscopy, no other unwanted impurity related peaks were found which indicates the impurity-free growth of GZO. Noodle, seed and granular-like structures of GZO/GaN, GZO/Al2O3, and GZO/Si have been revealed via Field-emission scanning electron microscopy micrographs respectively. The morphological analysis suggested GaN substrate as the best candidate for uniform and better quality GZO thin films. Highest carrier mobility (53 cm2/V s) with higher carrier concentration (> 1020 cm−3) has been found with low (1800) laser shots. Fivefold photoluminescence enhancement in the noodle-like structure of GZO/GaN with compared to GZO/Al2O3 and GZO/Si has been recorded. As the noodle-like structure supposed to be a more favorable structure for enhanced optical properties of GZO which points toward shape-driven optical properties. Theoretical (3.539 eV) and experimental (3.43, 3.6 eV) values of band-gap were found quite comparable. Moreover, lowest resistivity (3.5 × 10−4 Ω cm) with 80% transmittance is evident for GZO as a successful alternate of ITO.