Subpicosecond time-resolved Raman spectroscopy of LO phonons in GaAs-${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As multiple-quantum-well structures

Time-resolved Raman spectra of GaAs-${\mathrm{Al}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As multiple-quantum-well structures have been measured with subpicosecond time resolution. The average electron–LO-phonon scattering time for the electrons occupying the unbound states is resolved and found to be about 170 fs and is not affected appreciably by the well thickness.