Self-trapping-enhanced carrier recombination at light-induced boron-oxygen complexes in silicon

First-principles study of the BO$_{2}$ complex in B-doped Czochralski silicon reveals a self-trapping-enhanced carrier recombination mechanism that contrasts with the standard fixed-level Shockley-Read-Hall model for recombination. An O$_{2}$ dimer distant from the boron causes only a slow carrier recombination, which is, nevertheless, enough to drive the O$_{2}$ diffusion under light to form the BO$_{2}$ complex. We find that the BO$_{2}$ and O$_{2}$ produce nearly identical defect levels in the bandgap. Despite that, recombination at the BO$_{2}$ is substantially faster than that at the O$_{2}$, because the charge state of the latter inhibits a key step in the recombination, namely, the capture of the hole. This work was supported by the U. S. Department of Energy, BES and EERE, under Contract No. DE-AC39-98-GO10337.