AlN/GaN superlattices (SL) grown by metalorganic vapor-phase epitaxy with the period of SLs varied from 20 nm to 140 nm, and the thickness of the structures ranged from 0.7 to 1 μm were studied by polarized Raman spectroscopy technique. The peaks within a complex spectral feature of the symmetry A₁(TO) observed at about 580 cm^-1, were assigned to the interface and quasi-confined phonons. Frequency splitting between the peaks was found monotonously increasing along with the SL period. This dependence was explained using the dielectric continuum model. A method based on this finding was proposed for estimating the period SL using Raman spectroscopy. This method extends the traditional approach based on the studies of folded acoustic phonons in the short-period SLs.