Unusual phonon mode behaviour in zinc-blende BN/GaN superlattices

Comprehensive calculations of the long-wavelength optical phonons are reported for zinc-blende BN films by exploiting a linear response theory to simulate far-infrared reflectivity and transmission spectra at oblique incidence. A rigid-ion-model is used to study the lattice dynamics of the unconventional BN/GaN short-period superlattices (SLs). Besides empathizing, the anisotropic mode behaviour of optical phonons, the study has offered evidence of acoustic-mode anti-crossing, mini-gap formation, confinement, as well as BN-like modes falling between the gap regions separating the optical phonons of the two bulk (BN, GaN) semiconductor materials. A bond-polarizability approach within the second-nearest-neighbour linear-chain model is also employed to visualize the Raman intensity profiles of the short-period BN/GaN SLs, revealing major trends of the phonon characteristics noted in many conventional SLs, while eliciting some interesting contrasts.