By combining through-focus high-resolution transmission electron microscopy and hierarchical multi-scale simulations, consisting of density-functional theory, analytical empirical potentials and continuum elastic theory, the existence of a new dislocation type in GaN was demonstrated. In contrast to previously identified or suggested dislocation structures in GaN, all of the core atoms were fully coordinated. That is, no broken bonds occurred. This implied that the dislocation should be electrically inactive. However, the giant local strain-field around the dislocation core, in combination with the small lattice constant of GaN, caused deep defect states - and thus electrically active edge dislocations - independently of the specific core structure.

Strain Induced Deep Electronic States around Threading Dislocations in GaN. L.Lymperakis, J.Neugebauer, M.Albrecht, T.Remmele, H.P.Strunk: Physical Review Letters, 2004, 93[19], 196401 (3pp)