Density functional theory calculation of theDIoptical center in SiC

Abstract

The ${\mathrm{D}}_{I}$ center is a prominent defect which is detected in as-grown or irradiated SiC. It is unusual in that its intensity grows with heat treatments and survives anneals of $1700\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$. It has been assigned recently to either a close-by antisite pair or to the close-by antisite pair adjacent to a carbon antisite. We show here using local density functional calculations that these defects are not stable enough to account for ${\mathrm{D}}_{I}$. Instead, we assign ${\mathrm{D}}_{I}$ to an isolated Si antisite and the four forms of the close-by antisite pair in $4H\text{\ensuremath{-}}\mathrm{Si}\mathrm{C}$ to the $a$, $b$, $c$, and $d$ members of the alphabet series. The assignments allow us to understand the concentration of ${\mathrm{D}}_{I}$ following growth, the recombination enhanced destruction of these alphabet defects and the annealing behavior of the remaining members of the series.