Chemical mechanical polishing of free-standing GaN substrates is found to reduce the reverse leakage current of Ni/Au Schottky diodes fabricated on the Ga-face. The barrier height extracted from current voltage measurements is found to increase from similar to 0.4 eV on un-treated substrates to 0.75 eV on polished wafers, along with a reduction in diode ideality factor from 2 to 1.5. The electrical measurements are consistent with removal of a defective near-surface region that promotes generation-recombination current. More acidic polishing solutions were found to produce the best Schottky diode characteristics and there was an optimum loading force during CMP of the GaN surface. (C) 2008 Elsevier B.V. All rights reserved.