Optical Properties of ZnCdSe/ZnSSe Strained-Layer Quantum Wells

Abstract

We have shown the optical properties of ZnCdSe/ZnSSe strained-layer single- and multiple-quantum wells (SQWs and MQWs) fabricated by metalorganic molecular beam expitaxy (MOMBE). Excitonic emission and absorption properties were investigated in detail by means of photoluminescence, photoluminescence excitation and absorption spectral measurements. A multiple longitudinal optical (LO)-phonon emission which is related to the relaxation of hot excitons has been observed in the photoluminescence excitation spectrum in a SQW. The temperature dependence of the emission intensity in the SQWs with three different well widths (10, 50, and 100 Å) shows the quenching of the exciton-emission intensity. For a 10 Å well the dependence shows Arrhenius thermally activated behavior, where the activation energy of about 70 meV is obtained. A theoretical analysis of the temperature dependence of an excitonic linewidth indicates that the exciton-LO phonon coupling constant is estimated to be 35 meV which is larger than that (5 meV) of GaAs/AlGaAs QW. As a result, this effect is the dominant cause of the exciton linewidth broadening.