Theoretical investigation of edge dislocations in AlN

The structures and formation energies of neutral and charged edge dislocations in AlN are investigated via density-functional-theory calculations. Stoichiometric structures having full and open cores are considered as well as nonstoichiometric structures having aluminum or nitrogen vacancies along the dislocation core. Formation energies are found to depend strongly on the Fermi level, due to the presence of defect levels in the band gap, and on growth conditions for the case of the nonstoichiometric structures. A structure having aluminum vacancies along the dislocation core is predicted to be most stable in n-type material grown under nitrogen-rich conditions, whereas a nitrogen-vacancy structure is most stable in p-type material grown under aluminum-rich conditions. Estimates are also given for defect energy levels in the gap. (C) 1998 American Institute of Physics.