ANISOTROPY OF ZONE-CENTER OPTICAL PHONONS IN (GAAS)(N) (ALAS)(M) SUPERLATTICES/

We present a study of the anisotropy of zone-centre optical phonons in (GaAs)(n)/(AlAs)(m) superlattices by Fourier-transform infrared spect roscopy. We show that the reflection spectra of semiconductor superlat tices taken at off-normal incidence of the light contain information a bout both confined phonons propagating normal to the layers and interf ace phanons propagating in the plane of the layers. The frequencies of confined and interface modes obtained from reflection spectra are com pared with those calculated by dielectric continuum theory.