Multiphonon resonant Raman scattering in the semimagneticsemiconductor Cd1−xMnxTe:Fröhlich and deformation potential exciton–phonon interaction

Abstract

A theory describing multiphonon resonant Raman scattering (MPRRS)processes in wide-gap diluted magnetic semiconductors is presented,with Cd1−xMnxTeas an example. The incident radiation frequency ωl istaken above the fundamental absorption region. The photoexcited electron andhole make real transitions through the LO phonon, when one considers Fröhlich (F)and deformation potential (DP) interactions. The strong exchange interaction,typical of these materials, leads to a large spin splitting of the exciton states inthe magnetic field. Neglecting Landau quantization, this Zeeman splittinggives rise to the formation of eight bands (two conduction and six valenceones) and ten different exciton states according to the polarization of theincident light. Explicit expressions for the MPRRS intensity of secondand third order, the indirect creation and annihilation probabilities, theexciton lifetime, and the probabilities of transition between different excitonstates and different types of exciton as a function of ωl andthe external magnetic field are presented. The selection rules for all hot excitontransitions via exciton–photon interaction and F and DP exciton–phononinteractions are investigated. The exciton energies, as a function ofB, the Mnconcentration x, andthe temperature T,are compared to a theoretical expression. Graphics for creation and annihilationprobabilities, lifetime, and Raman intensity of second and third order arediscussed.