Determination of the Exciton Binding Energy in ZnCdSe Quantum Wells by Resonant Raman Scattering

Due to the relevant role of excitonic emission in blue-green diodes and lasers based on Zn1–xCdxSe quantum wells important efforts, in theory and experiment, have been carried out to determine the excitonic binding energy as a function of composition and quantum well width. In this work we present a direct determination of the binding energy of the free exciton of a 50 A Zn0.74Cd0.26Se quantum well confined by ZnSe barriers by means of the observation of the resonant Raman scattering (RRS) effect. We show that the RRS is due to a double resonance: the first (incoming) is produced by the matching of the exciting laser line (488 nm, 2.5407 eV) with the 1hh 1e absorption transition of the QW; the second (outgoing) is due to the close coincidence of the exciton binding energy and the LO phonon energy. From these results we have obtained 32.6 ± 2 meV for the free exciton binding energy.