We demonstrate that maskless wet etching of self-assembled Ge quantum dot (QD) multilayers can create large-area photonic nanostructures, and the geometry can be tuned by changing wet etching conditions. It is found that the reflectance in the near-infrared wave length can be decreased by controlling geometry, and an increase in the depth of the photonic nanostructures results in enhancement of photoluminescence intensity from Ge QDs. These results show that control of geometry in photonic nanostructures is useful for enhancement of optical absorption in the Ge QD multilayers. (C) 2013 Elsevier B.V. All rights reserved.