Deep-level photoluminescence in semi-insulating CdTe(In) and CdTe(Sn)

Photoluminescence (PL) of two groups of samples was investigated. One group was doped with Sn having a deep level near the middle of the forbidden gap. The second group was doped with In, which acts as a shallow donor. The nature of the deep levels in CdTe:In is not well known so far. A very intensive PL at deep levels is observed in case of CdTe:Sn samples. The intensity is approximately two orders of magnitude higher than in In-doped samples. Comparison of the radiative recombination activity at deep levels (0.3–1.2 eV) with the total PL signal (0.3–1.6 eV) shows that ∼0.2–1% of radiative recombination occurs at deep levels in case of CdTe:In samples and 7–15% in case of CdTe:Sn. A qualitative correlation between the mobility-lifetime product of electrons and the integral PL intensity at deep levels was observed. A correlation between integral PL intensity of A-centers and deep levels in CdTe:In samples was found. This supports the idea that the deep levels in CdTe:In samples are primarily complexes formed together with A-centers. The integral PL in the spectral range of deep levels can therefore serve as an indicator of sample quality from the point of view of its suitability for fabrication of detectors of gamma and X-ray radiation.