in an InGaAs/(110)InP, a CuAu-I type ordered structure is formed during growth with a propagation of two-monolayer steps (2-MLSs). The numerical calculation with an empirical interatomic potential has suggested that the ordered InGaAs clusters are stabilized at kink edges of the 2-MLSs. We confirmed that In and Ga adatoms preferentially occupy the upper and lower sites at a kink of 2-MLS, respectively. This explains that the CuAu-I type ordered structure which is made of alternately stacked In- and Ga-rich (110) planes is formed by propagation of the 2-MLS with kinks. Our Monte Carlo simulation using the ordering model showed that the ordered structure is actually formed at the growth temperature (similar to 700 K). (C) 7000 Elsevier Science B.V. All rights reserved. PACS: 68.55 (Epitaxy); 68.35.R (Phase transitions at surface and interfaces); 73.61.J (Semiconductor thin films); 07.05.T (Computer modeling and simulation).