Surface states in m.i.s. devices of cadmium sulphide

Measurements of the shunt conductance of m.i.s. diodes of cadmium sulphide, formed by depositing gold on to surfaces of crystals previously etched in hydrochloric acid, are interpreted to suggest that there is a density of surface states of the order of 2.0 X 1011 cm-2 eV-1 at the interface between the CdS and the semi-insulating layer. Comparison of the voltage intercept of the C-2/V plots with the photoelectric threshold suggests that the etching leaves a semi-insulating layer with a thickness of 400?600 A on the surface of the CdS.