Effect of substrate temperature on photo-electronic properties of thermally evaporated Zn Se thin films

The dark and photoconductivity of ZnSe thin films deposited at substrate temperature (Ts) range 303K to 623K were measured. The conductivity (σd) of the films were ∼ 10-6 Ω-1 m-1 at room temperature and were found to decrease with Ts. The activation energies were evaluated from the ln σd versus 103/T plots which showed two activation processes in the ambient temperature range 303K to 453K. The activation energy showed an independent trend with Ts. It was found that the as-grown films possessed poor photosensitivity, however their photosensitivity improved after suitable thermal annealing of the films. The decay time of the photosensitive films were of the order of minutes which indicated an exponential distribution of traps. Different trap depths, estimated from decay law were correlated with the electrical measurements. (author)