The effect of the Ga/N ratio upon the structure of threading dislocations in films which had been grown by means of molecular beam epitaxy was studied. Electrical measurements which were performed on samples that had been grown under Ga-rich conditions exhibited a 3 orders of magnitude higher reverse bias leakage as compared with those grown under Ga-lean conditions. Transmission electron microscopy revealed the presence of excess Ga at the surface termination of pure screw dislocations, accompanied by a change in the screw dislocation core structure in Ga-rich films. A correlation of the transport and transmission electron microscopy results indicated that the dislocation electrical activity depended sensitively upon the dislocation type and growth stoichiometry.

Effect of Growth Stoichiometry on the Electrical Activity of Screw Dislocations in GaN Films Grown by Molecular-Beam Epitaxy. J.W.P.Hsu, M.J.Manfra, S.N.G.Chu, C.H.Chen, L.N.Pfeiffer, R.J.Molnar: Applied Physics Letters, 2001, 78[25], 3980-2