Raman spectra of folded acoustic phonons in short-period GaN/AlN superlattices as a tool for structure characterization

The results of experimental and theoretical studies of phonon modes in short-period GaN/AlN superlattices grown by PA MBE on the (0001) Al₂O₃ substrate are reported. In the framework of Density Functional Theory and Elastic Continuum Model the lattice dynamics properties are studied of (GaN)_m(AlN)_n SLs (m+n≤24), where n and m are the number of monolayers. Good agreement between experiment and theory is found, which made it possible to establish unambiguously a relationship between the features observed in the Raman spectra and the microscopic nature of the acoustic phonon modes. The obtained results open new possibilities for analyzing the structural properties of GaN/AlN SLs by Raman spectroscopy.