The characteristics of anisotype CdS/CdTe heterojunction

Polycrystalline CdTe and CdS films were prepared by thermal evaporation technique with thicknesses 1.0 μm and 0.1 μm, respectively. The prepared films were deposited at substrate temperature 423 K, then annealed under vacuum at various annealing temperatures. Anisotype CdS/CdTe heterojunction has been prepared. The structure of the films was examined by X-ray diffraction. Hall measurements confirmed the conductivity types for CdTe and CdS to be p- and n-, respectively. Electrical characteristics of the junction (C–V and I–V measurements) showed that the junction was abrupt. Heat treatment (Ta) of the junction caused a decrease in the capacitance with increasing the reverse bias voltage. Also, both zero bias capacitance and built in voltage are decreased with increasing Ta. Carrier concentration around the junction was increased with increasing Ta. Transport mechanism of forward current coincides to tunneling-recombination mechanism; this was confirmed by I–V measurement.