Deep-center photoluminescence in nitrogen-doped ZnSe

In this paper, we report optical studies of nitrogen-doped ZnSe epilayers grown by molecular-beam epitaxy. Photoluminescence spectra of the donor-acceptor pair region at different temperatures and different carrier concentrations show that two donors are present in the samples: residual shallow donors with activation energy 26 meV and deep donors with activation energy of 4 meV previously assigned to a VSe-Zn-NSe complex. In the exciton region, we observe an emission at 2.765 eV, which shows an increased intensity when the epilayer is compensated by the deep donor. We therefore propose that this transition may be related to a deep-donor bound exciton.