Carbon Interstitial Diffusion in 3C‐SiC: Role of Charge‐State Transitions and Entropy

As a radiation‐resistant wide‐bandgap semiconductor, the self‐healing capability of 3C‐SiC is highly dependent on the diffusion of carbon interstitials (Ci). However, understanding of the thermodynamic and kinetic behaviors of Ci diffusion under various influencing factors remains limited. In this work, first‐principles calculations reveal a strong dependence of the diffusion free‐energy barrier on charge states, Fermi level, and temperature. The entropic effects on the diffusion process at finite temperatures are systematically explored using machine learning force field and enhanced sampling techniques. Notably, appropriate n‐type doping and entropic effects contribute to the suppression of free‐energy barrier for the Ci diffusion process. A Ci diffusion activation temperature diagram is constructed, taking into account charge‐state transitions and entropic contributions. Furthermore, the kinetic diffusion coefficients under different conditions are quantitatively evaluated. Major native point defects have also been assessed to clarify their role in promoting or inhibiting Ci diffusion. These findings provide a fundamental understanding of the thermodynamic and kinetic behaviors of Ci diffusion, offering physical insights into the defect evolution in 3C‐SiC.