This work deals with short period GaN-AlN superlattices, studied by Raman spectroscopy using visible and ultraviolet excitations. The E₂ (high) and E₁ (TO) phonons show a two-mode behavior. In contrast, we observed an unique spectral line in the A₁ (TO) spectrum: its dependence on the mean superlattice composition is in good agreement with recent theoretical results predicting its delocalized character. Two Raman lines strongly enhanced under ultraviolet excitations, were observed in the A ₁ (LO) spectrum. Lattice dynamical simulations within the Rigid Ion Model have been performed to assign these Raman lines. The first one corresponds to an A₁ (LO) phonon confined in GaN wells. The second line is assigned to a dispersive B₁ - like mode with an amplitude modulation similar to that of an interface mode.