Donor-acceptor pair bands in ZnSe

The donor-acceptor pair (DAP) bands have been studied in single crystals of ZnSe grown by vapor-phase epitaxy, from solutions of Ga, and In, and also by liquid-phase epitaxy. The temperature dependence of both steady-state photoluminescence and time-resolved spectra was used to identify the DAP bands R₀, Q₀, P₀ associated with Li and Na dopants. The DAP band Q₀ at 2.695 eV was already identified by Merz et al. as due to AlZn⁺-LiZn^-. We have associated the DAP band P₀ due to transitions involving AlZn⁺ donor and NaZn^- acceptor and the DAP band R₀ due to transitions involving a shallow donor and LiZn^- acceptor, respectively. This shallow donor level seems to be associated with the presence of Li in ZnSe and could be Liᵢₙₜ⁺. From these studies we obtain the acceptor level due to NaZn, 124±{}2 meV, and the shallow donor associated with Liᵢₙₜ as {≈} 26 meV, respectively. This study suggests that compensation in ZnSe may be related to background donor impurities such as Liᵢₙₜ rather than native defects.