Resonant first- and second-order Raman scattering in ZnTe

The resonance of the first- and second-order Raman spectra of ZnTe has been measured at room temperature in the region of the E0 edge using tunable cw dye lasers and ion lasers. The allowed first-order TO scattering is always weaker than the corresponding component of the allowed LO scattering, a fact which is interpreted in terms of the electro-optic coefficient. The forbidden LO scattering for the parallel-parallel polarization (Fröhlich interaction) becomes stronger than the allowed scattering near resonance. The second-order spectra were separated into irreducible components. Their most strongly resonant parts are a 2LO resonance (1 component) and an LO-TO resonance (15 component). These resonances are interpreted as iterated first-order processes involving the Fröhlich interaction. The rest of the second-order spectra resonates in a manner similar to the allowed first-order spectra. It is therefore attributed to electron-two-phonon interaction vertices. Its strongest feature corresponds to 2TA overtones (1 component). 2TO and 2LO overtone scattering is negligible. From the ratio of first- to second-order scattered intensities and the deformation potential d0 for the electron-one-phonon interaction, values of several electron-two-phonon deformation potentials are determined.