GaN thermal transport limited by the interplay of dislocations and size effects

Measurements and first-principles calculations probe the temperature-dependent thermal conductivity $(k)$ of GaN films with large densities of highly oriented dislocations. We demonstrate that phonon-dislocation scattering is weaker than suggested by previous measurements, likely due to sample and experiment size effects. Nonetheless, dislocation-limited k is observed in samples with large dislocation densities and at lower temperatures where k anisotropy is also observed. Combination of experiment and theory give insights into the interplay of thermal resistance mechanisms limiting GaN functionalities and suggest pathways for tuning k via defect engineering.