We study the growth of (In,Ga)As on GaAs (3 1 1)A and (3 1 1)B substrates by molecular-beam epitaxy (MBE). Wire-like structures and a matrix of closely packed cells develops, respectively, on (3 1 1)A and (3 1 1)B substrates, when the (In,Ga)As layer thickness exceeds a critical value for the onset of surface undulation due to the strain-driven growth instability. The established lateral strain distribution generates a unique template controlling nucleation and growth of (In,Ga)As quantum dots (QDs). On GaAs (31 1)B, the InAs QDs formed on the (In,Ga)As template exhibit pronounced improvement of the structural and optical properties. (C) 2002 Elsevier Science B.V. All rights reserved.