Influence of spontaneous and piezoelectric polarizations on the phonon frequencies in strained GaN/AlN superlattices

The influence of spontaneous and piezoelectric polarizations on the lattice dynamics of a strained GaN/AlN superlattice is investigated within a macroscopic framework. It is found that both effects alter the effective strain in the growth direction of the heterostructure in a significant way. This change in the strain state can also be connected to the internal strain in the GaN and AlN layers. The effects result in a change of the phonon frequencies of GaN and AlN of about 1 and 2 cm^-1, respectively.