We investigated the surface of ordered InGaAs alloys lattice-matched with InP(0 0 1) substrates during and after growth using reflectance difference or reflectance anisotropy spectroscopy (RDS or RAS). Bulk atomic ordering was investigated by Raman spectroscopy and ex situ RDS measurements. We observed that a (2 x 3) surface during growth is a trigger for the bulk cation ordering in the InGaAs/InP(0 0 1) system. Furthermore a (4 x 3) structure was observed after the growth stopped. In terms of RD measurements, a c(8 x 6) or (8 x 3) surface structure, including one-dimensional disorder boundaries, are possible structures for the two observed surfaces. (C) 2004 Elsevier B.V. All rights reserved.