Indian Journal of Science and Technology

Abstract

Schottky barrier photodiode of zinc sulfide (ZnS) thin film have been fabricated by thermal evaporation method. The ntype ZnS thin films of thickness 400 nm were deposited onto glass substrates at 150°C. The photodiode was form by evaporation of gold thin films on the n-type ZnS films and evaluated as UV near visible detectors. ZnS thin films were checked by using X-ray diffraction (XRD); the result shows that the films were polycrystalline. The lattice constant for ZnS films was calculated and it was 5.41Ao . The absolute quantum efficiency of the photodiode was measured for wavelengths between 200-600 nm. The responsivety of the prepared photodiodes of different thickness of gold thin films (50, 80 & 100 nm) was measured for wavelengths at the range as mentioned above. These detectors have negligible response to wavelengths longer than 340 nm which correspond to energies less than the band gap of the zinc sulfide. Finally the barrier height of diode was measured by the C-V method and found as low as 1.9 V.
Keywords: Schottky barrier, thermal evaporation method, zinc sulfide, gold thin films.