We have investigated the initial growth of InAs on Si(1 1 1) substrates produced with metal-organic vapor phase epitaxy (MOVPE) and using micro-channel selective area growth (MC-SAG). Treatment of the Si surface prior to InAs growth is essential in order to achieve high-yield nucleation of a single island in each growth area. A breakthrough for successful nucleation was the use of tertiarybutylphosphine (TBP) pre-flow. We have analyzed the effect of such surface pretreatment in terms of the shape of InAs islands at the initial stage of growth and the incubation period between the supply of the indium source and the nucleation, the latter data being obtained by means of in situ surface reflectivity measurement. XPS analyses confirmed that the TBP and tertiarybutylarsine (TBAs) pre-flow introduced, respectively, P and As on the Si surfaces resulting in a change in surface energy. The surface with As exhibited a larger surface energy and shorter incubation period, which are preferable for better nucleation. The coverage of As on the surface, however, appeared less reliable than that of P, i.e., pre-flow with TBP was superior to pre-flow with TBAs in terms of uniformity of surface coverage. This finding is useful for achieving high-yield nucleation in small growth openings in MC-SAG. (C) 2009 Elsevier B.V. All rights reserved.