The electronic structure of pure edge threading dislocations in metal-organic vapour-phase epitaxially grown wurtzite thin films was studied directly by means of atomic resolution Z-contrast imaging and electron energy loss spectroscopy in a scanning transmission electron microscope. The dislocation cores in n-type samples which were grown under N-rich conditions revealed no evidence of the high concentration of Ga vacancies which had been predicted by theoretical calculations. Instead, the vacancy concentration was between 0 and 15%. The N K-edge spectra which were collected from edge dislocation cores exhibited a sudden marked increase in intensity, of the first fine-structure peak immediately above the edge onset, as compared with the bulk spectra. This reflected the reduced C6v symmetry of the core. No absorption was observed below the band-gap, and this was consistent with the dislocation line being negatively charged.

Direct Experimental Observation of the Local Electronic Structure at Threading Dislocations in Metalorganic Vapor Phase Epitaxially Grown Wurtzite GaN Thin Films Y.Xin, E.M.James, I.Arslan, S.Sivananthan, N.D.Browning, S.J.Pennycook, F.Omnès, B.Beaumont, J.P.Faurie, P.Gibart: Applied Physics Letters, 2000, 76[4], 466-8