We report on the effect of the arsenic precursor and growth temperature on atomic ordering of InGaAs alloy nearly lattice-matched to InP grown by metalorganic vapor phase epitaxy. The optical properties, microstructure and surface morphologies show that the samples grown at 570-600 degreesC with the trimethylarsenic have some characteristic features: (i) a strong power-dependent redshift of the photoluminescence peak position relative to the band-gap; (ii) the presence of CuPt ordered structures as seen by high resolution transmission electron microscopy and transmission electron diffraction pattern; and (iii) a high surface density of islands as observed by atomic force microscopy. Ordering is seen for trimethylarsenic-grown epilayers up to 600 degreesC growth temperature, while it is not observed for arsine-grown epitaxial layers at the same growth temperature. A link between the surface morphology and the underlying chemical order as a result of the surface processes leading to the chemical ordering for trimethylarsenic-grown epilayers is discussed. (C) 2003 Elsevier B.V. All rights reserved.