Grating-coupler excited interface phonons in GaAs/AlAs superlattices

The optical phonon modes of short-period GaAs/AlAs superlattices were inves tigated by means of far-infrared reflection spectroscopy using the grating coupler technique. Grating couplers provide a wavevector transfer parallel to the layers, enabling us to study the in-plane dispersion of the phonon m odes in the superlattice structure, The fundamental longitudinal and transv erse confined phonons of GaAs and AlAs were detected. For an increasing in- plane wavevector transfer the superlattice phonon modes show dispersion due to interface effects. (C) 1999 Elsevier Science Ltd. All rights reserved.