Influence of preparation conditions on electron trapping in CdS polycrystalline layers

CdS layers have been prepared by conventional thermal evaporation, electron bombardment and sputtering. Thermally stimulated currents and photocurrent decay have been used to determine the trap depth E T and the electron capture cross section sigma n . The levels displayed on the layers studied are the same as those in single crystals and the different preparation conditions are only able to favour or suppress certain types of trap. However the traps attributed to interstitial cadmium are always present. sigma n values are similar to those measured for CdS single crystals except for the D levels, for which levels, values of sigma n for CdS layers are greater than those for single crystals.