Resonant Raman scattering in silicon

The resonance of the Raman scattering from the zone-center optical phonon in silicon has been measured over a wide energy range covering the 3.4-eV direct band gap. The experimental results are compared with both a theory deriving the Raman cross section from the optical constants and an ab initio calculation; good agreement is found in the region where the respective theories are expected to be reliable. The second-order Raman spectrum of silicon has also been measured at laser frequencies between 1.65 and 3.72 eV. Above the 3.4-eV gap, we observe a strong peak in the second-order spectrum corresponding to scattering from two optical phonons near the Γ point. From the resonance behavior of the second-order scattering, several electron-two-phonon deformation potentials are determined.