Monte Carlo simulation framework of decoupling phonon scattering mechanisms: A case study of bulk and nanowire GaN materials

A comprehensive phonon Monte Carlo (MC) simulation framework is proposed to systematically decouple and quantitatively evaluate the respective contributions of intrinsic phonon–phonon scattering, boundary scattering, and defect scattering mechanisms to phonon thermal transport in bulk and nanowire GaN materials. Within the framework, an intrinsic scattering model is developed to extract intrinsic scattering parameters from limited first-principles results and implement them in MC simulations. This model demonstrates the relative deviations below 3.8% for the intrinsic thermal conductivity of idealized GaN among analytical predictions, first-principles results, and MC simulations. Boundary and defect scattering models are subsequently incorporated into the framework to extract non-intrinsic scattering parameters from experimental thermal conductivity measurements of both bulk and nanowire GaN samples. For the bulk GaN, the analysis reveals that boundary scattering dominates phonon thermal transport behavior near 0 K, with its detrimental influence on phonon thermal transport progressively diminishing as temperature increases, becoming negligible above ∼100 K. In contrast, defect scattering manifests stronger phonon transport impedance than boundary scattering above ∼20 K. The nanowire system exhibits markedly different behavior: both boundary and defect scattering demonstrate substantially enhanced impedance effects throughout the entire experimental temperature range, with defect scattering exhibiting stronger impedance than boundary scattering above ∼100 K. Furthermore, distinct temperature-dependent defect scattering behaviors have been identified between the bulk and nanowire GaN materials. The established framework not only provides quantitative insights into the interplay of various scattering mechanisms but also offers a robust computational platform for investigating phonon thermal transport in practical micro/nanostructured materials and devices.