Influence of thickness and substrate temperature on electrical and photoelectrical properties of vacuum-deposited CdSe thin films

Polycrystalline cadmium selenide thin films are prepared in different thicknesses and substrate temperatures by vacuum deposition technique. The XRD patterns recorded for the CdSe thin films show that these films are polycrystalline in nature and crystallise in the hexagonal form. The crystallinity increases with increase in substrate temperature. The optical measurements reveal that the CdSe thin films possess direct band gap and the band gap energy decreases with the increase of thickness and substrate temperatures. The electrical conductivity measurements show that they possess three different activation energies in the temperature range 298 to 118 K. The steady-state photoconductivity measurements reveal that the photocurrent varies linearly with the applied voltage and the photocurrent obeys a power law of the form, Iph∝Fγ, where γ is a constant. The transient photoconductivity measurements show that the decay process is very rapid in the beginning followed by a slow process.