Phonon transport across a Si-Ge interface: the role of inelastic bulk scattering

Understanding phonon transport across heterojunctions is important to achieve a wide range of thermal transport properties. Using the McKelvey-Shockley flux method with first-principles modeling, we theoretically investigate the phonon transport properties of a Si-Ge interface with a focus on the role of inelastic bulk phonon processes. We observe significant inelastic scattering near the interface that redistributes the heat among the phonons as a result of non-equilibrium effects driven by the junction. These effects are most pronounced when the length of the junction is comparable to the average phonon mean-free-path. What controls these inelastic processes is elucidated.