Modeling phonon thermal conductivity in spatially confined GaN nanofilms under stress fields and phonon surface scattering

Thermal performance of nanomaterials has always been a significant part of semiconductor research, which is the key problem in the development and design of various micro/nanoelectronic devices. In this work, we investigate the thermal properties of prestressed gallium nitride nanofilms based on phonon Boltzmann transport approach and acoustoelastic theory. The influence of surface/interface scattering and stress fields on phonon properties and thermal conductivity is taken into account to predict the thermal conductivity of gallium nitride nanofilms. Theoretical calculations show that the phonon surface scattering and prestress fields can modify phonon thermal conductivity of gallium nitride nanofilms significantly. The compressive stress increases thermal conductivity whilst the tensile stress decreases thermal conductivity, and phonon surface scattering decreases the conductivity of gallium nitride nanofilms. With the decrease of the structural size, the surface scattering effect is enhanced, making phonon thermal conductivity a few orders of magnitude smaller than bulk value. This work could be helpful in optimizing the phonon thermal conductivity of nanomaterials through the stress/strain engineering and the surface/interface engineering. It can also provide a piece of theoretical evidence for the design of high-performance nanodevices.