Raman Scattering by Coupled Optical-Phonon-Plasmon Modes in GaAs

Raman scattering by coupled optical-phonon-plasmon modes has been studied in five differently doped GaAs samples in order to determine the linewidths and polarization of the coupled modes. The linewidths have been related to a lifetime which is predominantly due to individual electron collisions, although evidence is presented for Landau damping in the purest sample studied. The polarization data show that the plasma Raman scattering is comparable in magnitude to the phonon Raman scattering. The excitation wavelength was 9698 \AA{} from the ionized xenon laser.