Resonant First- and Second-Order Raman Scattering in GaP

The dependence on laser frequency of the scattering cross section for allowed and forbidden first-order Raman scattering and for second-order scattering is presented. The measurements were performed in the vicinity of the E₀ and E₀+Δ₀ gaps. It is shown that the Γ₁₅ components of the Raman tensor exhibit a sharp resonance at E₀ while Γ₁ components resonate both at E₀ and E₀+Δ₀. The results are interpreted in terms of a theory which assumes parabolic bands extending to infinity. The second-order scattering is produced mainly by electron-two-phonon interaction vertices, except for the strongly resonant sharp peaks which correspond to the creation of two LO phonons with →k0(Γ₁) and one LO plus one TO phonon with →k0(Γ₁₅). From these measurements, values for the electron-two-phonon deformation potentials are obtained.