Phonon transport across semiconductor interfaces

Knowledge of interfacial phonon transport, especially across semiconductor interfaces, is crucial for optimizing the thermal performance of microelectronics. Some calculations have suggested inelastic scattering and impurities at the interface enable an increase in thermal conductance, which helps heat dissipation. However, there is still limited information about under what conditions these approaches will play a role. Here, we experimentally investigated these effects on facilitating interfacial phonon transport. We built our high-quality metal/semiconductor interfaces by molecular beam epitaxy and accurately determined the thermal conductance using time-domain thermoreflectance. Our results show that inelastic phonon transport can occur across atomically sharp Al/Si and Al/GaN interfaces, serving as an additional transport channel to increase thermal conductance. Such a channel strongly depends on the interface sharpness rather than acoustical dissimilarity of materials forming the interface, clarifying the key factor of its occurrence. Besides, introducing interfacial disorder by adding alloyed interlayers including In_xGa_1−xN or Al_xGa_1−xN at the Al/GaN interface will not significantly alter its thermal conductance, regardless of varying lighter and heavier impurities with a concentration from 5% to 20%. As the alloyed interlayer has low thermal conductivity, introducing an interlayer will reduce the thermal conductance of Al/GaN instead of enhancing it. Our studies provide new insights on phonon transport across interfaces and open up opportunities for interfacial thermal design of high-power devices.