Electronic charge effects on dislocation cores in silicon

Using first-principles calculations, we investigate electronic charge effects on the structural stability of partial dislocations in silicon. For the 30degrees partial dislocation, we find that the unreconstructed core sustains all possible charge states associated with the dislocation-related electronic bands, as the Fermi level (mu(e)) sweeps the electronic band gap, while the reconstructed core remains neutral for p-type doping and intrinsic regimes. Both core configurations become negatively charged for n-type doping. In the case of the 90degrees partial dislocation, the three known core configurations (namely, the single-period and double-period reconstructed cores and the unreconstructed one) remain neutral in the p-type and intrinsic regimes, but the negatively charged states become stable in the n-type region, for all three geometries. More important, we find that the relative stability between the three structures is strongly charge-state dependent, with the unreconstructed core becoming energetically favorable in the n-type regime. Our results provide elements for understanding the role of doping on dislocation mobility in semiconductors. (C) 2004 American Institute of Physics.