On the Core Behavior of Dislocations in the Covalent Semiconductors C, Si and Ge

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Abstract
We use a tight-binding (TB) type electronic theory to calculate the core structure and core energy of both screw and 60° dislocations in the covalent semiconductors C, Si and Ge. To represent the repulsive interaction between atomic sites i and j, arising mainly from the core orthogonalization, we introduce a Born-Mayer potential. From the total (attractive and repulsive) energy calculations, we investigate the stability of dissociated partial dislocations. We show that the glide-set dissociated dislocations are more stable than the corresponding shuffle-set perfect dislocation, in agreement with recent experimental observations. The calculated results are also compared with available experimental results on the structure images and the dynamic properties of dislocations. In addition, we investigate the electronic states (sp configuration) of the dangling-bond-like states (DBLS) near the core of the partial dislocations, and discuss the validity of using fixed sp3 hybrid orbitals for calculating the dislocations.