Sputter-Deposited CdS Films with High Photoconductivity through Film Thickness

Photoconductive films of CdS have been sputter deposited by using mixtures of Ar–H2S as the sputtering gas in a diode system. Both rf and dc sputtering yield deposition rates of about 1 μm/h on substrates maintained above 200°C. Dark resistivities in excess of 107 Ω cm have been obtained with decreases of 5 orders occurring in the resistance when illuminated with a tungsten light source of approximately 0.5 W/cm2. As deposited, the CdS films have displayed photoconductive gain and also have much shorter decay times than films which are activated after deposition. Adherence has been excellent on suitably cleaned substrates and films in device structures have tolerated tensile strains in excess of 10−3 without adherence failure. No aging or electrode migration has been observed.