Thermal Resistance of Silicon/germanium Interfaces from Lattice Dynamics Calculations

INTRODUCTION Phonon scattering at the interface between two materials results in a thermal resistance, R [1]. An ability to accurately predict the thermal resistance of semiconductor interfaces is important in devices where phonon interface scattering is a significant contributor to the overall thermal resistance (e.g., computer chips with high component density). This ability will also lead to improvements in the design of semiconductor superlattices with low thermal conductivity, desirable in thermoelectric energy conversion applications [2]. The two most common theoretical models for predicting the thermal resistance of interfaces are the acoustic mismatch and diffuse mismatch models [1]. While these models have been successful in predicting the thermal resistance of isolated interfaces at temperatures less than∼30 K [1], they can be an order of magnitude in error at room temperature and above. Neither of these models account for how the atomic-level detail of the interface or the interaction between neighboring interfaces affect the thermal resistance. Furthermore, these models are usually applied under the assumption of linear phonon dispersion (i.e., the Debye approximation) [3–6], which is inaccurate at typical application temperatures, where phonons with wavelengths on the same scale as the interatomic spacing are excited [7]. Here, we use lattice dynamics (LD) calculations, which account for the atomiclevel detail of the interface and provide a realistic description of the phonon dispersion, to examine the effect of interface separation distance on the thermal resistance of Si/Ge interfaces.