44036-AC10
Intrinsic Lattice Thermal Conductivity of Nanostructured Semiconductor Systems
The main focus of this project is to develop accurate theoretical approaches to calculate the intrinsic lattice thermal conductivity, k(i), of bulk and nanostructured materials. Toward this end, during this reporting period we have completed our calculations of the intrinsic thermal conductivity of Si/Ge-based and GaAs/AlAs superlattices combining the adiabatic bond charge model for phonon eigenmodes with an exact iterative solution of the phonon Boltzmann equation. Through calculations of the temperature dependence of k(i), we have indirectly demonstrated a larger role of interface scattering than predicted from a relaxation time approach, which is consistent with recent measurements. We have also continued our development and implementation of a first principles approach to calculate k(i) for bulk semiconductors. For silicon and germanium, two of the most common semiconductors, we have found excellent agreement between our theoretical results and experimentally measured values of k(i) .vs. temperature using no adjustable parameters. We have now obtained similarly accurate results for diamond. We are currently extending our ab initio calculations to treat zinc blende structures. The results for bulk materials obtained thus far suggest that this first principles approach could provide predictive capability to aid in the design of new materials for thermal management applications.
