Raman signals and phonon sidebands under resonant excitation of donor - acceptor-pair states: spectroscopy with enhanced sensitivity to local vibrational excitations
We have investigated the Raman signals of vibrational modes and the phonon sidebands of resonantly excited donor - acceptor-pair recombination in p-doped CdTe and ZnSe. Under resonant excitation of donor - acceptor-pair states we observe an enhanced sensitivity of the optical spectroscopy to the spectrum of local vibrational excitations. The measured signals are interpreted as local vibrational modes of the dopants or as phonons with wavevectors at distinguished points of the Brillouin zone others than the centre point . These latter signals correspond either to the maxima of the phonon density of states of the host crystal or to longitudinal optical phonons with finite but discrete wavevectors defined by the donor - acceptor-pair separations. The results can contribute to the characterization of the materials as well as to the investigation of the processes of the acceptor compensation.