Influence of Substrate Temperature on Structure and Properties of Nb-Doped β-Ga2O3 Films

Nb-doped β-Ga2O3 films were deposited on p-Si (100) and quartz substrates using radio frequency magnetron sputtering technology at various substrate temperatures. All the films annealed in an argon ambient. The surface morphology and crystal structure of the films were studied using atomic force microscope and x-ray diffraction technologies, and the results indicated that the film had a flat surface and a good crystal structure when the substrate temperature was 523 K. We investigated the optical properties of the samples, and the results highlight that Nb-doped β-Ga2O3 films exhibit high transmittance of above 80% to UV–visible light with a wavelength above 400 nm. Furthermore, the optical band gap of the Nb-doped β-Ga2O3 films decreases with increasing substrate temperature. The electrical characteristics show that the current is larger, and that the contact between the Ag electrode and the Nb-doped β-Ga2O3 film is an ohmic contact, when the substrate temperature is 523 K. All the results are beneficial for practical applications.