PROPAGATION AND ATTENUATION OF PSEUDO SURFACE ACOUSTIC MODES AT THE (111)-FACE OF A GAAS CRYSTAL STUDIED BY BRILLOUIN SPECTROSCOPY

Acquisition of Brillouin spectra for light scattered by the (111) free surface of GaAs provides the experimental determination of pseudo-sur face-mode velocities and their attenuation for all nonequivalent azimu thal in-plane directions. Observations were performed with pp and p-s polarization configurations. Good agreement between measured and calcu lated velocities of the pseudo surface modes is achieved. A reasonable correlation;between the azimuthal behavior of the pseudo-surface-mode attenuation and that of the linewidth of the Brillouin satellites cor responding to these modes is obtained.