Self-assembled InAs quantum dots (QDs) in an InAl(Ga)As matrix, which is lattice-matched to InP substrate, were grown under various growth conditions by a molecular beam epitaxy and their structural and optical properties were investigated by atomic force microscopy (AFM) and photoluminescence (PL) spectroscopy. From the AFM and PL results, the nucleation of an InAs QD was significantly affected by the growth conditions for the buffer layer, that is, the surface characteristics of the buffer layer. Inserting a thin GaAs layer with a thickness of 0.6-1.8 nm controlled the optical and structural properties of InAs QDs due to the different growth front, different growth behavior of group III elements at the interface between the QD and the barrier, and modulation in strain field. (C) 2003 Elsevier B.V. All rights reserved.