Displacement damage induced disorder and thermal transport degradation in AlGaN alloys: A molecular dynamics study

Abstract

High electron mobility transistors based on AlGaN are widely deployed in radiation rich environments, where displacement damage can degrade both material integrity and heat dissipation. Yet, how displacement induced disorder couples to thermal transport degradation in AlxGa1−xN alloys across composition and temperature remains unclear. Molecular dynamics simulations were used to quantify radiation-induced structural disorder and thermal transport degradation in AlxGa1−xN random alloys. Defect accumulation was tracked by Frenkel pair analysis, while structural decoherence was quantified by a tetrahedra based local order parameter distribution and an amorphous-like atomic fraction defined from its low order weight. The composition response is nonmonotonic: Al0.5Ga0.5N exhibits the strongest defect retention and the largest growth of amorphous-like environments, whereas Al0.25Ga0.75N shows the weakest overall damage signature under the same dose. For a fixed composition, higher temperature systematically increases residual damage and raises the amorphous-like fraction, indicating that thermally assisted migration promotes persistent clustered and reconstructed states rather than restoring crystalline order. Radial distribution functions confirm the inferred disorder through peak broadening and rapid attenuation of medium-range oscillations, supporting the reliability of the tetrahedral metric. Equilibrium molecular dynamics calculations show that irradiation amplifies compositional sensitivity of thermal conductivity, with Al0.5Ga0.5N remaining the lowest after damage. The largest dimensionless thermal resistance increase coincides with the highest amorphous-like fraction in Al0.5Ga0.5N, while the temperature dependence of the relative resistance change reflects joint control by the pristine temperature-dependent transport baseline and the disorder level.