The applicability of Raman spectroscopy for estimation of interfaces thickness in the AlN/GaN superlattices

Polar optical phonons in quaternary nitride-based superlattices have been investigated in the framework of the dielectric continuum model. In the considered systems, the superlattice period consisted of two main GaN and AlN layers and two interstitial Al_0.5Ga_0.5 N layers. Such a structure simulates binary superlattices with diffuse interfaces. The presence of the finite thickness interface layers was shown to give rise to appearance of several low-intensity additional phonon modes active in Raman scattering; frequency splitting of such modes is sensitive to relative thickness of intermediate layers. The fundamental Raman-intense polar phonon modes were also stated to be independent on the interface thickness, and these modes were very sensitive to the main layer thicknesses.