Resonant hyper-Raman scattering in semiconductors: Excitonic effects

A theoretical model of resonant hyper-Raman scattering involving two incide nt photons of frequency omega(L) is developed. The model is valid for energ ies 2 (h) over bar omega(L) around the absorption edge of the semiconductor , and takes into account Wannier excitons as intermediate states in the sca ttering process. Both deformation potential and Frohlich interaction are in cluded in the model: It is found that Frohlich-mediated scattering is a dip ole-allowed process, in contrast to one-phonon Raman scattering, where the Frohlich mechanism is digole-forbidden. We have performed numerical calcula tions of the resonance profile (hyper-Raman cross-section versus 2 (h) over bar omega(L)) and applied our model to materials with dipole-allowed and d ipole-forbidden optical transitions. (C) 1994 Elsevier Science B.V. All rig hts reserved.