Electron beam induced current studies of MS and MIS devices on CdS

Schottky diodes, prepared by depositing gold onto single crystal CdS subjected to a variety of surface treatments, are investigated in the EBIC mode in a scanning electron microscope. The changes in the contrast observed when the polarity of the applied bias is changed are explained in terms of the penetration of the incident beam, and the voltage dependence of the width of the depletion region. Devices fabricated on surfaces which are mechanically polished exhibit features associated with localised defects, where the contrast reverses with change in polarity of the applied bias. This behaviour is shown to resemble that of MIS devices in which the insulating layer of silicon monoxide contained pinholes. A model is proposed to account for the observed phenomena. (author)