Optimum Metal-Semiconductor Contact for Cadmium Sulphide Thin Film

Activation Energy is an important feature in determining the formation of ohmic contact on a semiconducting material. Activation energy depends on workfunction of the semiconductor. Thus, there is a good co-relation between the ohmicity, activation energy and workfunction. In this work, Cadmium Sulphide (CdS) thin film of 2 µm thickness is the semiconducting material fabricated using Chemical Vapour Deposition (CVD) technique at different anneal temperatures in vacuum for 2 hours. From Four-probe, photo-response and spectroscopic measurements of CdS thin films, optimum anneal temperature is obtained. Aluminium, Nickel, Silver and Copper are the metallic contact points deposited on these fabricated films using Physical Vapour Deposition (PVD) technique. These Metal-Semiconductor (M-S) contacts are annealed in vacuum at 200ºC for 1hour. Current-Voltage (I-V) measurements are recorded for these M-S contacts at different temperatures. Electrical parameters are obtained for both un-annealed and annealed M-S contacts. Annealed M-S contacts give better results than un-annealed M-S contacts. The present paper has dealt with the estimation of optimum M-S contact on CdS thin film in the light of M-S contact parameters and activation energy