Coupled phonon–plasmon modes in indium phosphide observed by an ultrafastpump–probe technique

Abstract

We demonstrate that coupled phonon–plasmon modes in indium phosphide can be studiedby a time-domain technique by reporting the results of the ultrafast study of differentlydoped electron- and hole-type InP semiconductors. We have observed coherent oscillationswhose spectra comprise both phonon and plasmon modes. In p-type samples, the ultrafastpulses drive lattice modes that are coupled to the collective hole excitations for short timedelays only. In contrast, electron plasma seems to be coupled more strongly to the latticeand, as a result, the decay time of the coherence for the plasma modes is extended.