Damage accumulation and defect relaxation in4H−SiC

Abstract

A nonlinear dependence of damage disorder on dose is observed for both $\mathrm{Si}$ and $\mathrm{C}$ sublattices in $4\mathrm{H}\text{\ensuremath{-}}\mathrm{SiC}$ under $2\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$ Au irradiation at $165\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The relative disorder observed along the $⟨\overline{4}40\overline{3}⟩$ direction is much higher than that along the $⟨0001⟩$ direction. Molecular dynamics (MD) simulations demonstrate that most interstitial configurations are formed on the $\mathrm{Si}\text{\ensuremath{-}}\mathrm{C}$ dimer rows that are parallel to the $⟨0001⟩$ direction. As a result, these interstitials are shielded by the $\mathrm{Si}$ and $\mathrm{C}$ 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 $\mathrm{Si}$ sublattice and increases slightly on the $\mathrm{C}$ sublattice when measured along the $⟨\overline{4}40\overline{3}⟩$ direction due to relaxation of some metastable defects to lower energy configurations. As the annealing temperature increases, similar recovery behavior on both $\mathrm{Si}$ and $\mathrm{C}$ sublattices along the $⟨0001⟩$ direction indicates coupling of $\mathrm{Si}$ and $\mathrm{C}$ recovery processes; however, slightly higher recovery temperatures on the $\mathrm{C}$ sublattice along the $⟨\overline{4}40\overline{3}⟩$ direction suggests some decoupling of the $\mathrm{Si}$ and $\mathrm{C}$ recovery processes. Based on the structures and energetics of defects from MD simulations, new insights into defect configurations and relaxation processes are described.