Picosecond raman scattering from non-equilibrium collective modes in diamond and zincblende semiconductors

Abstract

Picosecond Raman scattering is a useful probe of non-equilibrium photo-excited carrier and phonon dynamics in group III-V and group IV semiconductors. In group III-V materials, time-resolved Raman scattering is used to explicitly demonstrate the strong long-range coupling of non-equilibrium free carriers with longitudinal optic phonon modes. This effect is exploited to provide a probe of the non-equilibrium free carrier density. In group IV materials, the absence of long range plasma-lattice interactions enables the generation and observation of non-equilibrium optical phonon modes in the presence of photo-excited plasma densities as high as 1 × 1019 cm−3. The non-equilibrium phonons in Ge and Gel–xSixalloys exhibit significantly different properties than those observed previously by others in GaAs and Gal–xAlxAs. © SPIE.