The electrochemical etching behaviors of GaAs on smooth and textured surfaces were systematically investigated in aqueous KOH electrolytes. When the applied potential was higher than the pore formation potential (PFP), the electrochemical etching of the smooth surface could be categorized into three regions: pore/wire formation, texturing, and electropolishing regions. Triangular GaAs nanowires were observed at low potentials while pronounced lateral etching occurred at high potentials. In the case of the textured surface, which consisted of groove arrays, more complicated etching behavior was demonstrated. The pore growth direction changed from < 1 1 1 > B to < 0 0 1 > at a high current density while accompanying a drastic change in the pore morphologies such as tetrahedron-like pores along (1 1 1)B transforming into 200 mu m deep pores propagated along the < 0 0 1 > direction. (C) 2011 Elsevier Ltd. All rights reserved.