In this works, CdTe was deposited on glass and Si substrates using thermal evaporation techniques. CdTe has been investigated from the properties (structural, surface morphological, optical and electrical). XRD analyses found the monocrystallite, cubic structure of the CdTe thin film and there is no trace of the other material. UV-Vis measurements indicate that 1.51 eV was found the energy gap of the CdTe thin film. Ag/CdTe/Si/Ag The heterojunction Photodetector has two response peaks located at 450 nm and 900 nm with a maximum sensitivity and detectivity of Ag/CdTe/Si/Ag 0.22 A/W and 3.1×1012 respectively.