Quasi-ballistic thermal transport in silicon carbide nanowires

Abstract

Silicon carbide (SiC) is an important industrial material that enables the thermal stability of power electronics. However, the nanoscale phenomenon of ballistic thermal conduction, which may further improve the thermal performance, remains unexplored in SiC. Here, we reveal the length and temperature scales at which SiC exhibits quasi-ballistic thermal conduction. Our time-domain thermoreflectance measurements probe the thermal conductivity of SiC nanowires as a function of their length and temperature. The deviation of the thermal conductivity from the diffusive limit in nanowires shorter than a few micrometers indicates the transition into a quasi-ballistic thermal conduction regime. Naturally, the deviation is greater at lower temperatures, yet the effect persists even above room temperature. Our Monte Carlo simulations of phonon transport support our experimental results and show how phonons with long mean free paths carry a substantial amount of heat, causing quasi-ballistic conduction. These findings show that quasi-ballistic heat conduction can persist at the microscale at operating temperatures of power devices, and thus may help improve the thermal design in electronics based on SiC.