The electrical charge state of threading dislocations in variously doped samples was investigated by scanning surface potential microscopy in conjunction with tapping mode atomic force microscopy. The dislocations were found to be either negatively charged or neutral, depending upon the type of dopant atom in the layers, i.e., Mg acceptors, Si donors, or without intentional doping. The results were interpreted in terms of decoration of the dislocations with other defects resulting in a partial compensation of the core charge by the accumulated surrounding charges.

Decoration Effects as Origin of Dislocation-Related Charges in Gallium Nitride Layers Investigated by Scanning Surface Potential Microscopy. A.Krtschil, A.Dadgar, A.Krost: Applied Physics Letters, 2003, 82[14], 2263-5