[en] Full text. We studied the atomic scale arrangement of interfaces in the Ga As/AlGaAs superlattices using Fourier-transform infrared spectroscopy and Raman scattering. Thus, the complete set of the characteristic optical frequencies (TO and LO modes in both Ga As and Al As frequency ranges) was analyzed, which gave us the possibility to obtain by the local-mode modification of an one-dimensional linear-chain model which takes into account the intermixture of Ga and Al in the same cation atomic plane. The ultrathin layer Ga As/Al Ga As superlattices grown by MBE have been investigated and correlation between the interface roughness and the optical phonon frequencies has been found. The analysis made in this work allowed us to obtain the real compositional profiles in the atomic scale in the superlattices studied. The experimental results reveal the evidence of alternation of the symmetry of optical confined modes caused by the 'different atomic arrangement of normal and inverted interfaces. (author)