Conducting atomic force microscopy and scanning surface-potential microscopy have been applied to image the surfaces of Mg-In-codoped GaN films grown by low-pressure metal-organic chemical-vapor deposition. Biscyclopentadienylmagnesium (CP2Mg) and trimethylindium (TMIn) have been used as the codoping sources in the experiment. The dislocation density at the film surface reduces to the lowest level (similar to 1.0 X 10(9) cm(-2)) when the TMIn/CP2Mg flow rate ratio is about 1. The dislocation density tends to rise when the flow ratio increases, and carriers of the film accumulate near the rim of the dislocation at an accelerated speed. The work function of dislocation is also found lower than that of nondislocation areas. Such electrical unevenness may seriously influence the light emission of the component, which should not be ignored during fabrication and deserves careful attention. (c) 2006 American Vacuum Society.