THEORETICAL INVESTIGATION OF EDGE DISLOCATIONS IN ALN

The structures and formation energies of neutral and charged edge disl ocations in AlN are investigated via density-functional-theory calcula tions. Stoichiometric structures having full and open cores are consid ered as well as nonstoichiometric structures having aluminum or nitrog en vacancies along the dislocation core. Formation energies are found to depend strongly on the Fermi level, due to the presence of defect l evels in the band gap, and on growth conditions for the case of the no nstoichiometric structures. A structure having aluminum vacancies alon g the dislocation core is predicted to be most stable in n-type materi al grown under nitrogen-rich conditions, whereas a nitrogen-vacancy st ructure is most stable in p-type material grown under aluminum-rich co nditions. Estimates are also given for defect energy levels in the gap . (C) 1998 American Institute of Physics.