Effects of surface/interface stress on phonon properties and thermal conductivity in AlN/GaN/AlN heterostructural nanofilms

The effect of surface/interface stress on phonon properties and thermal conductivity of GaN-based heterostructural nanofilms was theoretically investigated through the involvement of stress-dependent elastic modulus of nanostructures. The elastic model was used to quantitatively describe the spatially confined phonons in a GaN-based nanofilm under surface/interface stresses. The relationship between surface/interface stress and phonon thermal conductivity was further calculated for different phonon modes. Numerical results show that the positive (negative) surface/interface stress increases (decreases) the phonon energy and phonon group velocity while decreases (increases) the phonon density of state. With the increase of surface/interface stress, the phonon thermal conductivity of a nanofilm increases in SH mode but decreases in AS and SA modes. The surface/interface stress can also alter the temperature dependence of phonon thermal conductivity in heterostructural nanofilms. These simulation results will contribute to the analysis of heat transport in GaN-based heterostructural nanostructures and provide the theoretical support for the thermal performance design and optimization in GaN-based electronic devices.