Matryoshka phonon twinning in α-GaN

Lattice dynamics can govern the thermal conductivity solids and understanding the underlying mechanisms may enable enhanced performance of devices via judicious engineering. Here, insight into the anisotropic thermal conductivity of semiconducting alpha-GaN is gained by measuring the Matryoshka phonon dispersions. Understanding lattice dynamics is crucial for effective thermal management in electronic devices because phonons dominate thermal transport in most semiconductors. alpha-GaN has become a focus of interest as one of the most important third-generation power semiconductors, however, the knowledge on its phonon dynamics remains limited. Here we show a Matryoshka phonon dispersion of alpha-GaN with the complementary inelastic X-ray and neutron scattering techniques and the first-principles calculations. Such Matryoshka twinning throughout the basal plane of the reciprocal space is demonstrated to amplify the anharmonicity of the related phonons through creating abundant three-phonon scattering channels and cutting the lifetime of affected modes by more than 50%. Such phonon topology contributes to reducing the in-plane thermal transport, thus the anisotropic thermal conductivity of alpha-GaN. The results not only have implications for engineering the thermal performance of alpha-GaN, but also offer valuable insights on the role of anomalous phonon topology in thermal transport of other technically semiconductors.

Automated summary

By measuring the Matryoshka phonon dispersions, insights into the anisotropic thermal conductivity of semiconducting alpha-GaN have been gained, showing how phonon topology affects thermal transport in the material. This study demonstrates the importance of understanding lattice dynamics for effective thermal management in electronic devices.