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