We have successfully formed a thin twin-free layer on the top of InGaAs micro-discs by multi-step growth using micro-channel selective-area MOVPE on Si(1 1 1) substrates. The multi-step growth employs a gas flow sequence in which the partial pressure of the Ga source (trimethylgallium: TMGa) is modulated to control the initial nucleation and the direction of subsequent growth. We have previously improved in-plane uniformity of crystal shape of InGaAs micro-discs by 3-step growth that starts with InAs nucleation. Using these micro-discs as templates, InGaAs with tripled partial pressure of TMGa was grown as the fourth step. The growth of this fourth layer on the disc surface seems to suppress the layer-by-layer growth on the (1 1 1) plane and to terminate rotational twins, as well as keeping the size deviation of micro-discs under 25%. One of the most laterally grown micro-discs (with thickness of 380 nm and width of 7.1 mu m) had a 50-nm-thick twin-free layer on the top. (C) 2009 Elsevier B.V. All rights reserved.