Coherent phonons in Si- SiGe superlatticesReport as inadecuate

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1 CPMOH - Centre de physique moléculaire optique et hertzienne 2 LMP - Laboratoire de Mécanique Physique 3 UCSC - University of California Santa Cruz

Abstract : There are several classes of coherent phonons whose generation mechanisms are completely different: impulsive stimulated Raman scattering, Brillouin oscillations, and coherent longitudinal-acoustic-phonon Bragg reflection. All of these are investigated in Si- SiGe superlattices using a picosecond ultrasonics technique at room temperature. Bragg reflection for a single vibrational mode is related to gaps in the phonon-dispersion relation at the center and the boundary of the folded Brillouin zone. The two lowest minigaps are observed at 283 and 527 GHz. Theoretical calculations of phonon-dispersion relation and phonon reflection rate are given to explain experimental results.

Author: Younès Ezzahri - Stéphane Grauby - Jean-Michel Rampnoux - Hélène Michel - Gilles Pernot - W. Claeys - Stefan Dilhaire - Clém



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