Elastic strains and delocalized optical phonons in AlN/GaN superlattices

In the context of the dielectric continuum model, a correlation is established between the frequencies of delocalized $A$(TO) and $E$(LO) phonons in the Raman spectra of short-period AlN/GaN superlattices and the ratio between the layer thicknesses in the structure. It is shown that elastic strains produced in the materials of the layer during superlattice growth only slightly influence the correlation dependence of the frequencies of $A$(TO) and $E$(LO) modes with high intensities in the Raman spectra on the structural parameter defining the ratios between the layer thicknesses. The results of calculations of the phonon frequencies are in good agreement with available experimental data and can be used for spectroscopic diagnostics of AlN/GaN superlattices.