1ST-PRINCIPLES CALCULATIONS OF DISLOCATIONS IN SEMICONDUCTORS

The structure of dislocations in semiconductors and the effect of their interaction with impurities are examined using an ab initio local density functional cluster method. This method is entirely free from any empirical parameters and takes account of the charge transfer between the impurity and the host as well as the forces acting on core atoms. It is found that dislocations in Si are strongly reconstructed but B, P, N, and As impurities destroy this reconstruction. C impurities have little effect. Oxygen atoms form clusters which aggregate near dislocation cores and also lead to strong pinning effects. These results explain the strong pinning effects attributed to these impurities. In GaAs, beta-dislocations are strongly reconstructed but alpha-dislocations are not.