Light impurities and their interactions in silicon

The properties of isolated oxygen, carbon, nitrogen and hydrogen impurities in silicon are outlined. The precipitation of oxygen from solution is then discussed, first for temperatures above 500 degrees C and then for temperatures below 500 degrees C. It is at these lower temperatures that thermal donors are formed. To generate oxygen clusters containing up to say 10 atoms at 450 degrees C it is necessary to take dissociation of smaller oxygen clusters into account and also to invoke rapid diffusion of O-2 dimers. It is demonstrated that as-grown Czochralski crystals may contain hydrogen impurities that enhance the diffusion of single oxygen atoms, while these impurities are also incorporated in certain oxygen clusters that act as shallow donors. It is possible that dimer interactions with O-i atoms lead to enhancements in D-oxy.