Photoluminescence study of surface treatment effects on detector-grade CdTe:In

We studied the influence of standard surface treatment techniques on the generation of defects with deep levels that can act as trapping and recombination centers for photo-generated carriers in detector-grade CdTe:In material grown via the Vertical-Gradient-Freeze (VGF) method. We measured room-temperature contactless resistivity, photoconductivity, detector performance and low-temperature photoluminescence dependence on the surface preparation of the material and observed changes in the resistivity and photoluminescence signal after etching a 5 mu m thick surface layer. We found four deep levels in the range of 0.8-1.3 eV. The relative ratio of their photoluminescence maxima changes after mechanical polishing and chemical etching treatment. A deep level at similar to 0.9 eV seems to be connected to mechanical stress induced by polishing of the sample with a standard 1 mu m alumina abrasive and influences the charge collection efficiency of the detector.