Matryoshka phonon twinning in α-GaN

Abstract

Understanding lattice dynamics is crucial for effective thermal management in electronic devices because phonons dominate thermal transport in most semiconductors. α-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 α-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 α-GaN. The results not only have implications for engineering the thermal performance of α-GaN, but also offer valuable insights on the role of anomalous phonon topology in thermal transport of other technically semiconductors.

Anomalous Thermal Conductivity Induced by High Dispersive Optical Phonons in Rubidium and Cesium Halides

“…Modern computational techniques have been successfully utilized to probe novel physical behaviors, such as negative thermal expansion. [12] anisotropic thermal conduction, [13][14] and ultralow thermal conductivity. [15][16][17] Recent theoretical reports mainly take alkali halides as models to verify the accuracy of the improved prediction of thermal conductivity, [18][19] but the inherent thermal transport of alkali halides is rarely concerned.…”