GaAs nanopillars are fabricated using a combination of in situ self-organized local droplet etching of nanoholes in a semiconductor surface, nanohole filling with a different material, and ex situ material selective etching. The structural properties of the pillars are studied with atomic-force microscopy. Experimental pillar densities are analyzed using a scaling law. Furthermore, the thermal transport through ensembles of pillars is measured. The results show a clear correlation between the pillar density and the thermal conductivity which is several orders of magnitude reduced in comparison to the bulk. (c) 2012 Elsevier B.V. All rights reserved.