Electrochemical anodization using anodic alumina membrane-assisted etching of GaAs (111) B produced nanopatterned GaAs surfaces, which served as substrates for the growth of GaAs/InxGa1-xAs/GaAs quantum well (QW) nanowires with controllable size and density. The nanodepressions created on the anodized GaAs surface minimize the migration of Au nanodots during thermal annealing. The Au nanodots were used in vapor-liquid-solid based growth of the nanostructures. The thickness of the evaporated Au islands, the anodization voltage, and the duration of the etching are the most important parameters used to tailor the size distribution and density of the Au catalysts and hence the diameter of nanowires. Transmission electron microscopy (TEM) reveals that the QW nanowires are single crystals with the < 111 > main axis direction, similar to nanowires synthesized using conventional methods on bare GaAs substrates and other patterning mechanisms. Z-contrast high-angle annular dark-field scanning TEM confirmed the presence of the InGaAs layer having widths of 70-100 nm. Photoluminescence spectroscopy on the QW nanowires showed consistent peaks at 1.375 eV indicative of the first electron-heavy hole recombination from the InGaAs QW layer. This transition energy corresponds to a 0.10 In composition, in disagreement with the value obtained from energy-dispersive x rays in scanning TEM (x(EDX)=0.05). (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3498753}