Analysis of time-resolved donor-acceptor-pair spectra of ZnSe: Li and ZnSe : N

We measured the time-resolved photoluminescence of ZnSe : Li bulk crystals and ZnSe : N heteroepitaxial layers in the donor-acceptor-pair (DAP) transition region. We found nonexponential decay curves for all samples and all spectral positions except for luminescence from nearest DAPs. It is shown that the approach by Thomas et al. perfectly describes this overall behaviour for ZnSe : Li as well as for ZnSe : N if, for the latter, transitions from the deep donor to the shallow nitrogen acceptor are considered. Our fit of the decay curves yields a binding energy of (50 ± 2) meV for the deep nitrogen-related donor with an effective Bohr radius of (22.8 ± 0.6) Å.