Abstract
We employ density functional theory based phonon transport methods to provide a rigorous understanding of the nature of thermal transport in coherent short-period AlN/GaN superlattices (SLs), with period lengths up to three unit cells of each, and compare these with properties of their bulk constituents. Increasing the period length leads to phonon band folding with frequency gaps and thus smaller phonon velocities and more phonon scattering than in bulk, both of which reduce lattice thermal conductivity (κ). Contrary to expectations, we find that velocity variations among larger-period AlN/GaN SLs play only a minor role in cross-plane κ reductions, while variations in intrinsic phonon scattering are strongly correlated with their transport behaviors. This work provides insights into the microscopic behaviors of technologically relevant nanostructured materials, which are likely applicable to a wider range of SL systems and other nanostructures.
| Original language | English |
|---|---|
| Article number | 104310 |
| Journal | Physical Review B |
| Volume | 109 |
| Issue number | 10 |
| DOIs | |
| State | Published - Mar 1 2024 |
Funding
Calculations and development of the paper were supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Material Sciences and Engineering Division. B.B. and D.G.W. were supported in part by the National Renewable Energy Lab (Contract No. DE-FOA-0002252 CPS Agreement No. 38213). The calculations used resources of the Compute and Data Environment for Science (CADES) at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725, and resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. This work was conducted in part using the resources of the Advanced Computing Center for Research and Education at Vanderbilt University, Nashville, TN. We thank Xiaolong Yang, Tianli Feng, and Xiulin Ruan for providing four-phonon scattering rates for GaN.