Space-charge-limited currents and electron traps in cds crystals

Abstract

Thermally stimulated currents have been measured after the electrical injection of electrons in thin insulating crystals of cadmium sulphide which can support large space-charge-limited currents. Two trapping levels which lie 0.41 ev and 0.61 ev below the conduction band are filled with electrons when currents in the vicinity of the traps-filled limit are passed. When currents which lie within the region of Child's Law for solids are allowed to flow the concentration of trapping levels at 0.61 ev decreases while the number of levels at 0.41 ev increases. Measurements of the dark current in the ohmic region suggest that the 0.41 ev trapping complex is stable at temperatures below 0°C and is converted to a complex with a level at 0.61 ev at higher temperatures.