Phonon thermal conductivity of GaN nanotubes

Abstract

We theoretically investigated the phonon thermal conductivity of gallium nitride (GaN) nanotubes with diameters ranging from a few nanometers to 120 nanometers using the Boltzmann transport equation and took into account the phonon dispersion relations of the nanotubes and the influence of boundary scattering on the non-equilibrium phonon distribution. The calculation results show that the phonon thermal conductivity of GaN nanotubes is much lower than that of the bulk counterpart and it depends on the thickness, inner and outer diameters, and surface roughness of the nanotubes. A small thickness or a large surface roughness leads to a small thermal conductivity. The reduction of the phonon thermal conductivity of the nanotubes is mainly due to the decrease of the phonon group velocity, change of the phonon relaxation rate, and enhancement of phonon boundary scattering. The understanding and results on the thermal conductivity obtained in this work are important for the optoelectronic devices based on GaN nanotubes and nanowires, and the developed calculation method on the phonon thermal conductivity is generally applicable and can be used for other nanotube systems.