In this study, various surface cleaning techniques for the removal of contaminants from GaN were investigated. Auger electron spectroscopy (AES) analysis was used to monitor the presence of surface contaminants and atomic force microscopy (AFM) was used to monitor surface roughness. AES analysis showed that KOH was effective in removing carbon (C). Comparing the topographies of GaN surfaces cleaned in HCl, KOH and (NH4)(2)S in aqueous solutions; it has been found that surfaces cleaned in (NH4)(2)S is the best cleaned, have the lowest values of both C and O, RMS roughness and Ga/N ratio. The nearly complete removal of C and O were achieved by heating the samples in AES in vacuum. (c) 2004 Elsevier B.V. All rights reserved.