Bound-Exciton and Edge-Emission Spectra Associated with Li and Na Acceptors in ZnSe

Abstract

An alternative model for the radiative recombination process in ZnSe, responsible for the edge-emission bands associated with Li and Na acceptors, is tentatively proposed. This is derived from a recent experimental result showing that the energy level of a Na acceptor is shallower than that of a Li acceptor. The energy value of Na level is found to be 102 meV using results from direct observation of two-hole transitions. Significant Li contamination was observed in intentionally Na-doped ZnSe specimens which were heat-treated above 500°C. Both the Li bound exciton line and the related edge-emission band were found to decrease in intensity after prolonged exposure of the samples in air, whilst the Na bound exciton line remained constant.