Damage accumulation and defect relaxation in 4H-SiC

A nonlinear dependence of damage disorder on dose is observed for both Si and C sublattices in 4H-SiC under 2 MeV Au irradiation at 165 K. The relative disorder observed along the 〈4403〉 direction is much higher than that along the 〈0001〉 direction. Molecular dynamics (MD) simulations demonstrate that most interstitial configurations are formed on the Si-C dimer rows that are parallel to the 〈0001〉 direction. As a result, these interstitials are shielded by the Si and C atoms on the lattice sites, which significantly reduces the contribution of these interstitials to the backscattering/reaction yield along the 〈0001〉 direction. During isochronal annealing below room temperature, the relative disorder decreases along the (0001) direction, as expected; however, the disorder is stable on the Si sublattice and increases slightly on the C sublattice when measured along the (4403) direction due to relaxation of some metastable defects to lower energy configurations. As the annealing temperature increases, similar recovery behavior on both Si and C sublattices along the 〈0001〉 direction indicates coupling of Si and C recovery processes; however, slightly higher recovery temperatures on the C sublattice along the 〈4403〉 direction suggests some decoupling of the Si and C recovery processes. Based on the structures and energetics of defects from MD simulations, new insights into defect configurations and relaxation processes are described.