The fabrication and characterization of thermal evaporated n-ZnS/p-Si heterojunction and ZnS-Au Schottky photodiodes

The wide bandgap of zinc sulfide (ZnS) is optimum for the detection of UV wavelengths. In the research work presented here, thermal evaporated ZnS layer is paired with Si and Au to form heterojunction and Schottky photodiodes. The devices showed UV detection capabilities. The barrier height of the n-ZnS/p-Si heterojunction varied from 0.06 to 0.1 eV when the ambient temperature was increased up to 420 K. The series resistance and ideality factors varied from 20 to 130 k omega and 2-3 respectively. The built-in potential was about 0.76 V. The heterojunction showed a responsivity of 0.08 A/W and quantum efficiency of 0.3. The Au/ZnS Schottky junction was found to have an ideality factor of 2.53 with a barrier height of 0.46 eV. The response times of both the devices were found to be almost similar but it was much faster than that of the isolated ZnS film. This is due to the faster movement of photogenerated charges in the electric field of the junction.