Using atomic force microscopy and scanning surface potential microscopy, an investigation was made of the effect of extended dislocations (0.5 to 3μm) on the charge distribution in epilayers grown, by metalorganic chemical vapor deposition, onto (00▪1) sapphire. It was observed at the surface that the extended dislocations in undoped films were negatively charged; exhibiting an 0.04 to 0.2V higher potential, relative to regions that contained no dislocations. In addition to the higher potential at the dislocation core, the surrounding surfaces - including the edges of the dislocations - were also negatively charged in a symmetrical manner around the dislocations, revealing crater-shaped higher-potential regions (about 0.04V) relative to surrounding dislocation-free areas. Experimental results showed that the protrusion-type of dislocation was also negatively charged, and its potential was dependent upon the size of the dislocation.

Effects of Extended Dislocations on Charge Distribution in GaN Epilayer. H.Choi, E.K.Koh, Y.M.Cho, J.Jin, D.Byun, M.Yoon: Microelectronics Journal, 2005, 36[1], 25-8