Characterization of the 1117-meV and 1052-meV optical transitions in heat-treated Si.

Four conflicting models have been proposed for the origin of the ${\mathit{O}}^{\mathit{j}}$ and ${\mathit{O}}^{\mathit{j}\ensuremath{'}}$ photoluminescence transitions that are observed near 1117 and 1052 meV in heat-treated, oxygen-rich silicon. To distinguish between them we have investigated the effects on the optical transitions of magnetic and stress perturbations. We show that both the ${\mathit{O}}^{\mathit{j}}$ and the ${\mathit{O}}^{\mathit{j}\ensuremath{'}}$ lines are produced by recombination of excitons bound to isoelectronic centers of rhombic I (${\mathit{C}}_{2\mathit{v}}$) symmetry. The excitons have an electron derived from a pair of conduction-band minima and a hole in an orbital singlet state. The electronic states and the symmetry are reminescent of the thermal donors in silicon, supporting the suggestion that the ${\mathit{O}}^{\mathit{j}}$ and ${\mathit{O}}^{\mathit{j}\ensuremath{'}}$ centers may have evolved from them. There is clear evidence that both centers may trap one or two excitons, accounting for most of the luminescence structure, but the specific origin of one exciton-related weak line at both ${\mathit{O}}^{\mathit{j}}$ and ${\mathit{O}}^{\mathit{j}\ensuremath{'}}$ remains uncertain.