Growth and etching characteristics of gallium oxide thin films by pulsed laser deposition

The gallium oxide films were deposited on (0 0 1) sapphire at various substrate temperatures from 400 to 1000°C by pulsed laser deposition using a KrF excimer laser. The etching treatments for as-grown gallium oxide were performed in a 49 mol% HF solution at room temperature. The structural, optical and etching properties of the grown films were investigated in terms of high resolution X-ray diffraction, optical transmittance, atomic force microscopy, and X-ray photoelectron spectroscopy. The phase transition from amorphous to polycrystalline β-Ga ₂O ₃ structure was observed with increasing growth temperature. From the optical transmittance measurements, the films grown at 550-1000°C exhibit a clear absorption edge at deep ultraviolet region around 250-275 nm wavelength. It was found that the optical band gap of gallium oxide films increased from 4.56 to 4.87 eV when the substrate temperature increased from 400 to 1000°C. As the substrate temperature increases, the crystallinity of gallium oxide film is enhanced and the etching rate is decreased. The high etching rate of 490 nm s ^-1 for gallium oxide film grown at 400°C could be due to its amorphous phase, which is referred to higher void ratio and looser atomic structure.