UV Photodetector Based on p-NiO film/n-Si Heterojunction Prepared by Thermal Oxidation

Abstract

In this work, p-type NiO film was grown on n-type Si substrate as UV photodetector. NiO film was prepared over n-type Si (100) through two-step method. First, metallic Ni film was deposited on Si wafer using thermal evaporator; then the film was thermally oxidized in a tube furnace at 500 °C for 3 h to get NiO film. The film revealed polycrystalline structure of cubic NiO phase as confirmed from XRD characterization. The diffraction peaks ascribed to metallic Ni film were not detected in the XRD pattern which implies that Ni film was completely converted into NiO. For photoelectric measurements of NiO/Si heterojunction, Ag metal was deposited on both Si substrate and NiO film as a contact. The current-voltage curves exhibited rectifying behaviour with ideality factor and barrier height of 25 and 0.96 eV, respectively. NiO/Si heterojunction showed appreciable photoresponse towards UV light at wavelength of 365 nm. The responsivity, rise time and fall time of the photodiode were measured as 0.16 A/W, 1.7 s and 0.85 s, respectively at bias voltage of -5 V.