First-Principles Calculations of Dislocations in Semiconductors

Abstract

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, β‐dislocations are strongly reconstructed but α‐dislocations are not.

Structure and Energy of the90°Partial Dislocation in Diamond: A CombinedAb Initioand Elasticity Theory Analysis

“…Two approaches are common in the literature. The first approach is to study a "cluster" of atoms imposing the displacements expected from elasticity theory at the boundaries [3][4][5][6][7]. A second approach is to impose periodic boundary conditions [8][9][10].…”

Ordering of As impurities in a Si dislocation core

“…However, experimental 1-3 and theoretical [4][5][6][7][8][9][10][11][12] work has established that dislocations and grain boundaries in Si and Ge actually reconstruct in such a manner that all atoms are fourfold coordinated. Therefore, a single impurity atom occupying a substitutional site in the core does not experience any appreciable difference from its environment in the bulk material away from the core, resulting in small segregation energies.…”

“…These strains lead to larger segregation energies in a dislocation core than in the grain boundary, as high as ϳ0.9 eV per As atom. In earlier work using cluster calculations, Jones et al 7 found that As and P dimers in a dislocation core gain substantial energy by achieving threefold coordination. However, chains of threefold-coordinated impurities were not considered.…”

Stacking fault effects in pure and n-type doped GaAs

“…6,8,9 What is not clear so far is how or whether the interaction of point defects with a SF may affect the mechanical or electronic properties of semiconductors. Impurities have been found to segregate towards a SF in silicon, 5 suggesting that a SF may play an active role in the properties of the material.…”