Temperature quenching mechanisms for photoluminescence of MBE-grown chlorine-doped ZnSe epilayers

We report on a detailed investigation on the temperature-dependent behavior of photoluminescence from molecular beam epitaxy (MBE)-grown chlorine-dope d ZnSe epilayers. The overwhelming neutral donor bound exciton ((ClX)-X-0) emission at 2.797 eV near the band edge with a full-width at half-maximum ( FWHM) of similar to 13 meV reveals the high crystalline quality of the samp les used. In our experiments, the quick quenching of the (ClX)-X-0 line abo ve 200 K is mainly due to the presence of a nonradiative center with a ther mal activation energy of similar to 90 meV, The same activation energy and similar quenching tendency of the (ClX)-X-0 line and the I-3 line at 2.713 eV indicate that they originate from the same physical mechanism. We demons trate for the first time that the dominant decrease of the integrated inten sity of the I, line is due to the thermal excitation of the "I-3 center"-bo und excitons to its free exciton states, leaving the "I-3 centers" as effic ient nonradiative centers. The optical performance of ZnSe materials is exp ected to be greatly improved if the density of the "I-3 center" can be cont rolled. The decrease in the luminescence intensity at moderately low temper ature (30-200 K) of the (ClX)-X-0 line is due to the thermal activation of neutral-donor-bound excitons ((ClX)-X-0) to free excitons. (C) 2000 Publish ed by Elsevier Science B.V.