Multiple-scattering simulations, and experimentally obtained Z-contrast images and electron energy-loss spectra, were used to obtain a detailed analysis of the effect of the intrinsic structure of edge, screw and mixed dislocations on the local density of unoccupied states. It was shown that the multiple scattering method was especially useful for examining dislocation cores where the bonding was significantly different at each atomic site in the structure. Analysis of the nitrogen K-edge from intrinsic dislocations (stoichiometric cores with no dopants or vacancies) showed that the changes in the local electronic structure could be attributed to a change in the symmetry of the structure that did not result in easily identifiable states in the band-gap. It was concluded that the electrical activity at dislocations which limited the lifetime and performance of GaN devices appeared to be related to the segregation of dopants, impurities or vacancies.

Intrinsic Electronic Structure of Threading Dislocations in GaN. I.Arslan, N.D.Browning: Physical Review B, 2002, 65[7], 075310 (10pp)