Light-Induced Boron-Oxygen Recombination Centres in Silicon: Understanding their Formation and Elimination

Lifetime-degrading recombination centres - those that emerge in the presence of excess carriers in boron and oxygen containing silicon - show a peculiar dependence on the concentrations of the relevant impurities, B and O, and on the hole concentration P-0 (net doping) in materials that contain compensating donors (phosphorus or Thermal Donors) or added Ga acceptors. The data indicate involvement of both substitutional (B-s) and interstitial (B-i) boron atoms in the major recombination centres observed in p-Si. A suggested model ascribes degradation to the presence of a B1BsO latent defect inherited from the thermal history in a recombination-inactive atomic configuration. In the presence of excess electrons, this latent defect reconfigures into a recombination-active centre. The defect concentration dependence on the material parameters is reduced, in some special cases, to a proportionality to p(0) [O](2) or to [B] [O](2). The essential feature is an involvement of a fast-diffusing species Bi in the defect. This species can be removed to the boron nano-precipitates thus eliminating the defects responsible for the degradation.