INTERACTION OF IMPURITIES WITH DISLOCATION CORES IN SILICON

The interaction of P with 90-degrees partial dislocations in Si is examined using a cluster method with local-density-functional pseudopotential theory. This method is capable of predicting structural properties such as bond lengths and angles to within a few per cent. We describe several states of P at dislocation cores which are normally reconstructed and which contain solitonic reconstructed bonding patterns. Our overall conclusion is that there is a clear tendency for P to migrate towards the dislocation core, and assume threefold coordination, thus firstly breaking reconstructed bonds across the core and secondly passivating the solitonic dangling bonds. These different states can explain the segregation of P to a dislocation, its locking effect and its effect upon the dislocation velocity. The passivation of P also contributes to the effect of plastic deformation on the carrier densities.