6533b83afe1ef96bd12a7022

RESEARCH PRODUCT

Resonant hyper-Raman scattering in semiconductors

subject

description

A theoretical model for resonant hyper-Raman scattering by LO phonons is developed, taking into account excitonic effects. The model is valid for energies below and above an allowed absorption edge. The matrix elements corresponding to the exciton-photon and exciton-phonon interactions are derived analytically, and their contributions to the total scattering efficiency are analyzed. The two main electron-phonon interaction mechanisms present in polar semiconductors, deformation potential, and Fr\"ohlich interaction, are considered. It is shown that the one-phonon resonance hyper-Raman scattering mediated by the deformation potential interaction is dipole forbidden, whereas it is allowed when induced by the Fr\"ohlich mechanism, in contrast to what happens in one-phonon Raman scattering. The calculated hyper-Raman resonance profiles show two pronounced features: an incoming resonance with the $2p$ exciton state, and a much stronger outgoing resonance related to the s excitons. The numerical values obtained illustrate the suitability of this nonlinear scattering technique for the study of the exciton structure and the exciton-phonon interaction in large-band-gap semiconductors. Our theoretical description shows a good agreement with measurements performed on ZnSe films deposited on GaAs(001) substrates.