Radiation-induced amorphization and thermal conductivity degradation in GaN from multi-method simulations

Radiation-induced amorphization and the associated degradation of thermal transport properties pose critical challenges to the reliability of GaN-based power devices operating in extreme environments. Herein, the irradiation effects of high-energy protons and alpha particles on lattice structure and thermal conductivity of wurtzite GaN are systematically investigated using the combined Monte Carlo (MC) and molecular dynamics (MD) simulations. The MC simulations can characterize the energy deposition, primary knock-on atom energy spectra, and defect generation profiles induced by particle irradiation. Subsequent MD simulations reveal the structural evolution of cascade-induced damage, such as point defect formation, subcascade branching, and the development of local amorphous regions. To quantitatively describe the degree of amorphization, the local lattice destruction rate (LLDR), indicating a spatially resolved indicator of lattice disorder, significantly increases with the cumulative cascade collisions at lower temperatures, leading to more severe amorphization. Non-equilibrium molecular dynamics simulations further establish a strong linear correlation between LLDR and thermal resistance, indicating that irradiation-induced amorphization directly contributes to the degradation of thermal conductivity. Elevated temperatures are shown to mitigate both amorphization and thermal conductivity reduction by promoting defect recovery and lattice reordering. This study offers critical insights into the multi-method mechanisms governing radiation-induced structural damage and heat transport degradation in GaN, providing valuable guidance for the thermal management and design of radiation-tolerant GaN-based devices.