Luminescence and influence of defect concentration on excitons in $^{197}\!$Hg / $^{197}\!$Au-doped CdTe

CdTe, implanted with $^{197}\!$Hg ions, which decay to $^{197}\!$Au with a half-life of 64.1 h, was investigated by photoluminescence (PL) spectroscopy. The results unambiguously verify the assignments of both, the donor–acceptor pair transition at 1.335 eV, which corresponds to an acceptor level with E$\scriptstyle_{A}$=263 meV, and the recombination of excitons bound to neutral acceptors at 1.57606 eV to single Au atoms on Cd sites. In addition, the dependence of the intensities of excitonic lines on the defect concentration was investigated quantitatively. The observed intensities are well explained, assuming that a defect can only bind an exciton if there is no additional defect within the volume of the bound exciton. The ratio between the exciton radii of the Cu and Au-bound excitons R$\scriptscriptstyle^\textrm{Cu}_{exc}$ / R$\scriptscriptstyle^\textrm{Au}_{exc}$ = 1.2$\pm$0.2 obtained from this model is in good agreement with the ratio derived from the diamagnetic shift parameters of the two corresponding PL lines.