GaSb quantum rings (QRs) of different sizes and shapes were grown by metal organic molecular beam epitaxy (MOMBE). Partially capped InAs quantum dots (QDs) grown on a GaAs buffer layer were flattened by In-flushing, followed by regrowth of GaSb which forms ring structure around the InAs seed dots. With the assistance of such an InAs/GaAs groundwork layer, the GaSb QRs exhibit a better defined shape compared to the spontaneously formed rings. First, rims of QRs develop around the boundary of the InAs/GaAs, then additional GaSb QDs grow on top of them preferentially along the [0 - 1 1] direction compared to [0 1 1]. (C) 2011 Elsevier B.V. All rights reserved.