A method for preparing atomically smooth gallium nitride (GaN) surfaces that involves chemical etching with a platinum catalyst in water is presented. The flattened GaN(0001) surface exhibits periodic structures composed of straight-edged steps the height of a single bilayer. Atomic step and terrace structures containing an extremely small number of scratches and pits can be achieved on wafer scale (2 inch diameter). Photoluminescence analysis revealed that the intensity of band-edge luminescence increases significantly after flattening. Low energy electron diffraction indicated that the flattened GaN surface is crystallographically well-ordered. Current density between the wafer and Pt is observed when they are rotated, suggesting that the GaN surface is etched by an electrochemical reaction initiated by the tribo effect between Pt and the wafer surface. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.051204jes] All rights reserved.