New Mechanism for Non-Radiative Recombination at Light-Induced Boron-Oxygen Complexes in Silicon

First-principles study of BO2 complex in B-doped Czochralski silicon (Cz-Si) reveals a novel, self-trapping-enhanced carrier recombination mechanism, in sharp contrasts to the standard fixed-level Shockley-Read-Hall theory for carrier recombination. We found that an O2 dimer, distant from any B, would cause only weak carrier recombination under illumination -- only enough to drive its diffusion to find B and form the BO2 complexes. Surprisingly, BO2 and O2 produce nearly identical defect gap states. Despite this, recombination at BO2 is substantially faster than that at O2, because the charge state of the latter inhibits hole capture, the key step for such recombination.