Abstract
Local density functional calculations are used to investigate models of the center responsible for a prominent set of luminescent lines with zero-phonon lines around $3.15\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ in hydrogen rich $4H\ensuremath{-}\mathrm{Si}\mathrm{C}$ and previously attributed to ${V}_{\mathrm{Si}}\text{\ensuremath{-}}\mathrm{H}$. We find that the electronic structure of this defect and the character of its vibrational modes are inconsistent with this assignment. In contrast, a ${\mathrm{H}}_{2}^{*}$ center, bound to a carbon anti-site, is more stable than the isolated molecule and possesses a donor level close to that observed for the H-lines. Moreover, its vibrational modes are in good agreement with experiment. A possible mechanism for the radiation enhanced quenching of the defect is discussed.
Published Version
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