Self-assembled InAs quantum dots (QDs) on In0.52Al0.48As lattice matched to (1 0 0) InP substrates were grown by solid-source molecular beam epitaxy. We present in situ reflection high-energy electron diffraction studies of the initial growth processes and strain relaxation behaviors of the InAs QDs. The growth process of an InAs layer at the initial stage is clearly divided into two-dimensional (2D) growth and QD formation. It was found that the critical thickness for the 2D-3D transition is about two monolayers. The photoluminescence peak energies from the QDs were found to depend strongly on the InAs coverage, and the emission wavelength can be controlled over the 1.3-1.55 mum range.