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

Abstract

We report on a detailed investigation on the temperature-dependent behavior of photoluminescence from molecular beam epitaxy (MBE)-grown chlorine-doped ZnSe epilayers. The overwhelming neutral donor bound exciton (Cl 0X) emission at 2.797 eV near the band edge with a full-width at half-maximum (FWHM) of ∼13 meV reveals the high crystalline quality of the samples used. In our experiments, the quick quenching of the Cl 0X line above 200 K is mainly due to the presence of a nonradiative center with a thermal activation energy of ∼90 meV. The same activation energy and similar quenching tendency of the Cl 0X line and the I 3 line at 2.713 eV indicate that they originate from the same physical mechanism. We demonstrate for the first time that the dominant decrease of the integrated intensity of the I 3 line is due to the thermal excitation of the “I 3 center”-bound excitons to its free exciton states, leaving the “I 3 centers” as efficient nonradiative centers. The optical performance of ZnSe materials is expected to be greatly improved if the density of the “I 3 center” can be controlled. The decrease in the luminescence intensity at moderately low temperature (30–200 K) of the Cl 0X line is due to the thermal activation of neutral-donor-bound excitons (Cl 0X) to free excitons.