Structure of the 0.767-eV oxygen-carbon luminescence defect in 450 °C thermally annealed Czochralski-grown silicon

Abstract

The oxygen-carbon luminescence defects with no-phonon emission at 0.767 eV (``P line'') and 0.79 eV (``C line'') created in pulled silicon after 450 \ifmmode^\circ\else\textdegree\fi{}C thermal annealing or electron irradiation, respectively, are investigated in a comparative study. This includes investigation of all major local modes in samples $^{13}\mathrm{C}$ or $^{18}\mathrm{O}$ enriched to practically 100% abundances. Many new isotopic line shifts are observed on both spectra, and those already reported in the literature are confirmed. Striking similarities in the two vibronic sideband spectra, the sensitivity of the individual local modes to carbon or oxygen isotopic substitution, and the nearly identical electronic properties of the two defects lead us to conclude that the defects possess an identical ``core.'' The core structure is identified as the isolated interstitial carbon ${\mathrm{C}}_{\mathrm{i}}$ (a bonded carbon-silicon pair along 〈001〉 sharing a substitutional site) as adopted from the recently published model of the 0.79-eV center. The defects are distinguished by their oxygen structure (which for the 0.79-eV defect was identified as an interstitial oxygen atom ${\mathrm{O}}_{\mathrm{i}}$). We argue that in the 0.767-eV center a di-oxygen molecule or a more complex oxygen aggregate deriving from the molecule is bonded to ${\mathrm{C}}_{\mathrm{i}}$. Evidence for this is taken from literature data on di-oxygen formation kinetics and from our observation of the C line in heated silicon proving the presence of interstitial carbon as a result of self-interstitial generation in the process of oxygen pairing.