It is important to research the dependence of the capacitance and capacitance on the parameters on the photodiodes. In this article, we aim research experimental and theoretical on the nCdSpSi heterostructure. A heavily doped n+CdS layer with a thickness of about 50 Å was created by deposition of a thin layer of indium (In) for 25-30 s on the surface of a CdS film in vacuum with a residual pressure of 10-5Torr at a substrate temperature of 373 K, followed by annealing at 673 K in within 300s. Then, on the surface of this heavily doped n+CdS layer, a current-collecting “P”-shaped ohmic contact with an area of 3 mm2 was obtained also by the vacuum evaporation of In.