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 las ers based on Zn1-xCdxSe quantum wells important efforts, in theory and expe riment, 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 Z n0.74Cd0.26Se quantum well confined by ZnSe barriers by means of the observ ation of the resonant Raman scattering (RRS) effect. We show that the RRS i s due to a double resonance: the first (incoming) is produced by the matchi ng of the exciting laser line (488 nm, 2.5407 eV) with the 1hh -> 1e absorp tion transition of the QW; the second (outgoing) is due to the close coinci dence of the exciton binding energy and the LO phonon energy. From these re sults we have obtained 32.6 +/- 2 meV for the free exciton binding energy.