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 spectroscopy. We show that the reflection spectra of semiconductor superlattices taken at off-normal incidence of the light contain information about both confined phonons propagating normal to the layers and interface phanons propagating in the plane of the layers. The frequencies of confined and interface modes obtained from reflection spectra are compared with those calculated by dielectric continuum theory.