It is generally accepted that the Schottky barrier height (SBH) is affected by the initial band bending at the bare nGaN surface as well as by an additional contribution following metal deposition. In this work the effect of processing used for device fabrication on the surface band bending of bare c-plane nGaN was studied by surface potential electric force microscopy (SP-EFM). An increase of the initial upward band bending from 1.0 ± 0.1eV for the as-grown GaN to 1.9 ± 0.1eV after RTA treatment in N2 ambient was observed. No significant dependence of band bending on N2 or Ar as ambient gas during the RTA treatment was observed. The increase of the initial upward band bending was also confirmed by photoluminescence (PL) measurements. We suggest that the RTA treatment causes a high density of surface states, possibly as a result of high temperature reaction of ambient gas and remnant contamination.