Coherent phonons in Si/ SiGe superlattices

Younès Ezzahri (1) , Stéphane Grauby (1) , Jean-Michel Rampnoux (1) , Hélène Michel (1) , Gilles Pernot (1) , W. Claeys (1) , Stefan Dilhaire (1) , Clément Rossignol (2) , G. Zeng (3) , Ali Shakouri (3)

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

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.

Domaines: Science des matériaux [cond-mat.mtrl-sci]; Optique [physics.optics]; Acoustique [physics.class-ph]

Younès Ezzahri, Stéphane Grauby, Jean-Michel Rampnoux, Hélène Michel, Gilles Pernot, et al.. Coherent phonons in Si/ SiGe superlattices. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2007, 75 (19), pp. 195309. ⟨10.1103/PhysRevB.75.195309⟩. ⟨hal-01535961⟩