Impurity centers in ZnSe:Na crystals

The influence of sodium impurity on photoluminescence (PL) spectra of ZnSe crystals doped in a growth process from a Se+Na melt is investigated. It is shown that the introduction of the impurity results in emergence of emission bands in the PL spectra due to the recombination of exciton impurity complexes associated with both donors and hydrogen-like acceptors. Apart from that, four bands generated by donor–acceptor pairs recombination and a band produced by electronic transitions from the conduction band to a shallow acceptor are discussed. As a result of the analysis it is concluded that Na impurity forms in ZnSe lattice NaZn hydrogen-like acceptors with activation energy of 105±3 meV, Nai donor centers with activation energy of 18±3 meV, as well as NaZnVSe and NaiNaZn associative donors with activation energy of 35±3 and 52±9 meV, respectively.