A combination of atomic force microscopy and scanning capacitance microscopy was used to investigate the relationship between the surface morphology and the near-surface electrical properties of GaN films which had been grown onto c-axis sapphire substrates by means of metal-organic chemical vapor deposition. Local regions surrounding the surface termination of threading dislocations exhibited a reduced change in capacitance, with applied voltage, relative to those regions that contained no dislocations. Capacitance-voltage characteristics which were obtained for these regions indicated the presence of negative charge in the vicinity of dislocations.

P.J.Hansen, Y.E.Strausser, A.N.Erickson, E.J.Tarsa, P.Kozodoy, E.G.Brazel, J.P.Ibbetson, U.Mishra, V.Narayanamurti, S.P.DenBaars, J.S.Speck: Applied Physics Letters, 1998, 72[18], 2247-9