Photocurrent and Surface Photovoltage Spectroscopy Investigations of CdTe-based Compounds

The potentiality of photocurrent (PC) and surface photovoltage spectrosocopy (SPS) analyses in the determination of the band gap of CdTe-based ternary alloys was investigated. Both methods can detect band-to-band and defect state-to-band transitions. The role played by the surface states in both experimental methods has been studied since it may significantly alter the results. The below-band gap energy levels have also been detected by PC and SPS and the different information that can be obtained in the two cases has been discussed. The results obtained by PC and SPS have been compared in order to extract the contribution of the surface and bulk states.