Excitons in one-phonon resonant Raman scattering: Fröhlich and interference effects

A theoretical model of resonant Raman scattering including excitons as intermediate states in the process is compared with recent experimental results in some III-V compound semiconductors where the Raman polarizability was obtained in absolute value for several scattering configurations. In particular, Fr\"ohlich (F) interaction and its interference with the deformation potential (DP) one is analyzed in the E₀+Δ₀ critical point (CP) of GaAs at three different temperatures. Also the E₀ and E₀+Δ₀ CP of GaP and E₀+Δ₀ of GaSb are analyzed. We show that the inclusion of impurity-induced forbidden LO-phonon Raman scattering is not necessary when excitonic effects are considered. The experimental data of GaAs corresponding to F interaction can be fitted by assuming a Fr\"ohlich constant cF=0.14 eV A1/2. Lifetime broadenings of 12 meV (10 K), 14 meV (100 K), and 28 meV (300 K) are deduced. The lifetime broadening of GaAs and GaSb at 100 K are taken from two-phonon Raman scattering spectra where the incoming and outgoing resonances are well defined. The general features in the comparison with the experiment is that the measured spectra corresponding to F interaction are well fitted; however, the theoretical interference is stronger than the measured one.