Effect of growth stoichiometry on the electrical activity of screw dislocations in GaN films grown by molecular-beam epitaxy

The impact of the Ga/N ratio on the structure and electrical activity of th reading dislocations in GaN films grown by molecular-beam epitaxy is report ed. Electrical measurements performed on samples grown under Ga-rich condit ions show three orders of magnitude higher reverse bias leakage compared wi th those grown under Ga-lean conditions. Transmission electron microscopy ( TEM) studies reveal excess Ga at the surface termination of pure screw disl ocations accompanied by a change in the screw dislocation core structure in Ga-rich films. The correlation of transport and TEM results indicates that dislocation electrical activity depends sensitively on dislocation type an d growth stoichiometry. (C) 2001 American Institute of Physics.