Nano‐Scale Phonon Dynamics in GaN: Fundamentals and Strategies for Thermal Transport Modulation

ABSTRACT With the rapid advancement of electronic technologies, the effective thermal management in gallium nitride (GaN) ‐based devices has emerged as a critical challenge, particularly as device dimensions shrink to scales comparable to phonon mean free paths. In this regime, phonon‐mediated heat transport is governed by size‐dependent phenomena, such as boundary scattering, lattice confinement, and interface mode mismatch, which fundamentally deviate from bulk behaviors. Progress remains hindered by an insufficient understanding of phonon dynamics, resolution limits of characterization, and the inadequate incorporation of these insights into thermal management strategies. This review addresses these gaps by dissecting phonon‐dominated thermal transport in dimensionally confined GaN structures and at its heterointerfaces from both theoretical investigations and experimental characterizations. It further highlights the recent progress in in situ vibrational electron energy‐loss spectroscopy for the atomic‐scale visualization of phonon modes. Furthermore, the interface engineering between GaN and its adjunction materials is reviewed with strategies to minimize the thermal boundary resistance. Finally, future directions emphasize the integration of multiscale simulations, in situ characterization of multiple interfaces, and machine learning to deepen the fundamental understanding and optimize nano‐scale phonon transport for next‐generation GaN electronic applications.