Phonon transport governed by intrinsic scattering in short-period AlN/GaN superlattices

Here we employ density functional theory based phonon Boltzmann transport methods for rigorous microscopic insights into the nature of thermal transport in coherent short-period AlN/GaN superlattices (SLs) and compare these with properties of their bulk constituents. Increasing SL period leads to phonon band folding with frequency gaps, and thus smaller phonon velocities and more opportunities for phonon scattering, both of which reduce lattice thermal conductivity (k). Contrary to expectations, we find that velocity reductions in larger period SLs plays only a minor role in k reductions, while variations in intrinsic phonon scattering are strongly correlated with the transport behaviors.