Effects of Cd-vapor and Te-vapor heat treatments on the luminescence of solution-grown CdTe:In

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Abstract
We have employed cathodoluminescence at 80–300 K in the first comprehensive study of the effects of Cd-vapor or Te-vapor heat treatments on the luminescence of solution-grown CdTe:In. The broad 1.4-eV band present in as-grown material is weakened by Te firing and typically enhanced by Cd firing. These results do not support earlier connections between this luminescence and the VCd-InCd complexes predicted by defect chemistry calculations to be dominant in CdTe:In. Alternatives to straightforward interpretation are discussed for both experiments and defect modeling. The effects of the heat treatments on the injection-level dependence, frequency response, and temperature dependence of the 1.4-eV luminescence are described. This luminescence arises from localized transitions within compact complexes in our as-grown material, but different species of complexes or competing transition mechanisms are involved in heat-treated material. The edge emission, present in both as-grown and fired material, peaks near 1.57 eV at 80 K and thus is close to the band-gap energy of CdTe. However, frequency-response data reveal anomalous energy-storage processes which can slow the edge-emission kinetics to the microsecond regime following Cd firing. Another surprising result is the strong coupling in both kinetics and injection-level dependence between the edge emission and a sharp extrinsic band near 1.54 eV which is prominent in Te-fired CdTe.

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