Substrate effect and temperature dependence of thermal transport characteristics in GaN-based graphene

Graphene/GaN nanocomposites have important applications in GaN-based LEDs. Since the electrical transport characteristics of this composite have been widely studied, the thermal transport properties have not been systematically studied. Herein, the thermal transport properties of suspended graphene and graphene supported by GaN including length, substrate effect and temperature dependence are carefully studied by molecular dynamics (MD) simulation. When the length is 250 nm, the thermal conductivity of GaN-supported graphene is 1567.5±46.4 W/mK, which is about 85% of that for the suspended graphene at room temperature. More interesting, a theoretical model is used to describe substrate effect by modifying the phonon dispersion and density of states, and the conclusion of this model is consistent with our MD simulations. Moreover, the underlying mechanism of substrate effect and temperature dependence is revealed by spectral energy density (SED) analysis. Our study reports the finite suppression of GaN on the thermal conductivity of graphene, which provides insights for thermal management of GaN-based LEDs.