HOT-PHONON EFFECTS IN FEMTOSECOND LUMINESCENCE SPECTRA OF ELECTRON-HOLE PLASMAS IN CDS

The carrier intraband relaxation in CdS is studied with femtosecond ti me resolution using the luminescence up-conversion technique. The cool ing dynamics of high-density carriers clearly show the nonequilibrium buildup of high populations of certain modes for both longitudinal opt ical and acoustic phonons. The acoustic-mode disturbances develop on t he subpicosecond time scale and are observed as a transient reduction of the carrier energy-loss rate through the retardation of the optical -phonon decay (the effect of the ''acoustic-phonon bottleneck'').