Formation and annealing of nitrogen-related complexes in SiC

Abstract

We propose a mechanism for the annealing of vacancy-related defects in SiC, based on ab initio total energy calculations. Our mechanism is based on the formation and migration of carbon and nitrogen split interstitials resulting in ${\mathrm{C}}_{\mathrm{Si}}({\mathrm{N}}_{\mathrm{C}}{)}_{n}$ or ${V}_{\mathrm{Si}}({\mathrm{N}}_{\mathrm{C}}{)}_{n}$ complexes as intermediate annealing products: In as-implanted samples, only recombination of nearby defects is possible, e.g., the disappearance of divacancies can be explained by a formation of ${V}_{\mathrm{Si}}{\mathrm{N}}_{\mathrm{C}}$ pairs $(P12$ centers). Dissociation of these very stable pairs at temperatures below $2000\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ is not possible. At elevated temperatures above $1000\ifmmode^\circ\else\textdegree\fi{}\mathrm{C},$ further aggregation becomes possible, resulting in electrically and optically inactive ${V}_{\mathrm{Si}}({\mathrm{N}}_{\mathrm{C}}{)}_{4}$ complexes. The recombination with carbon split interstitials, resulting in ${\mathrm{C}}_{\mathrm{Si}}{\mathrm{N}}_{\mathrm{C}}$ and ${\mathrm{C}}_{\mathrm{Si}}({\mathrm{N}}_{\mathrm{C}}{)}_{2}$ donors, are discussed as competing processes.