Molecular dynamics study on the dependence of thermal conductivity on size and strain in GaN nanofilms

The thermal conductivity of GaN nanofilm is simulated by using the molecular dynamics (MD) method to explore the influence of the nanofilm thickness and the pre-strain field under different temperatures. It is demonstrated that the thermal conductivity of GaN nanofilm increases with the increase of nanofilm thickness, while decreases with the increase of temperature. Meanwhile, the thermal conductivity of strained GaN nanofilms is weakened with increasing the tensile strain. The film thickness and environment temperature can affect the strain effect on the thermal conductivity of GaN nanofilms. In addition, the analysis of phonon properties of GaN nanofilm shows that the phonon dispersion and density of states of GaN nanofilms can be significantly modified by the film thickness and strain. The results in this work can provide the theoretical supports for regulating the thermal properties of GaN nanofilm through tailoring the geometric size and strain engineering.