Oxygen-carbon, oxygen-nitrogen and oxygen-dimer defects in silicon

An ab initio local density functional cluster method, AIMPRO, is used to examine a variety of oxygen related point defects in silicon. In particular results are given for X-O-n complexes where X is interstitial C, N or O. For n=2, the first defect, C-O-2 has been assigned to the P-centre giving a PL line at 0.767 eV and seen in Cz-Si annealed around 450 degrees C. The second, N-O-2, has properties consistent with a nitrogen related shallow thermal donor. We have also found that a (C-H)O-2i defect has very similar electronic properties, and this implies that shallow thermal donors do not have a unique composition. The structure and migration energy of the oxygen dimer is considered and the dimer is found to migrate very much faster than a single oxygen atom.