Raman spectroscopy of hot electron relaxation in GaAs

The dynamics of non-equilibrium carriers injected into GaAs by either 5 or 0.5 picosecond laser pulses at 2.12 eV have been investigated by spontaneous Raman scattering. The LO phonons emitted by the "hot" carriers as they relax towards the band edges have been observed. The variation of the phonon population with time is consistent with a cascade model for electron relaxation. Non-equilibrium effects are also observed in the phonon-plasmon coupled modes for optically injected carrier concentrations < 1018/cm3