Effect of different substrates on the structural, morphological, electrical, and optical properties of β-Ga2O3 thin films deposited by the sol-gel spin coating method

Abstract

β-Ga₂O₃ thin films were successfully deposited on sapphire, quartz, and silicon substrates using a sol-gel spin coating method. This study aims to investigate the influence of different substrates on the properties of β-Ga₂O₃ thin films. The properties of the films were analyzed using various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM, TUNA), Fourier transform infrared (FTIR) spectroscopy, and ultraviolet-visible (UV-Vis) spectrophotometry. XRD analyses revealed that all deposited films exhibited a polycrystalline structure with a monoclinic β-phase, with the best crystallinity observed on the sapphire substrate, showing a crystallite size of 35.92 nm. SEM micrographs displayed a granular morphology with varying granule sizes. AFM (TUNA) analysis was used to examine surface morphology and current transport characteristics, showing that surface roughness increased from quartz to sapphire to silicon (2.94 nm, 4.8 nm, and 7.01 nm, respectively). Electrical resistivity increased in the order: quartz, silicon, and sapphire. The highest transmission, nearly 100% in the visible spectrum, was observed for the β-Ga₂O₃ film grown on the sapphire substrate, which also had a band gap of approximately 5.4 eV as evaluated from UV-Vis spectrophotometry.

Graphical Abstract