AbstractThe frequency spectrum of polar interface modes of superlattices is derived with regard of bulk spatial dispersion. The results are applied to free carrier excitations of superlattices. Dispersion relations are given for intra‐ and intersubband interface plasmon modes. It is shown that collective electronic excitations of superlattices considered in previous papers are limiting cases of interface plasmon modes. Experimental data on plasmon dispersion can be understood in terms of interface plasmon modes if carrier confinement is taken into accoun