Contributions of strain relaxation and interface modes to thermal transport in superlattices

Superlattice structures are widely used in electronic and optoelectronic devices, many of which depend heavily on thermal management for performance and reliability. It has been observed that silicon/germanium superlattices exhibit an enhancement in thermal conductivity at very short period lengths, which has been attributed to the contribution of coherent phonons. Here we investigate additional potential contributions to enhanced thermal conductivity in superlattices as period length is reduced, finding that a reduction in strain relaxation as well as increased contributions of interface modes that have vibrational character intermediate between those of the two constituent materials offer additional mechanisms for increased thermal conductivity.