We investigate the role of In desorption for (In,Ga)As self-organized quantum wire (QWR) formation on GaAs (100) based on elongated island formation, annealing, and stacking in (In,Ga)As/GaAs superlattice growth. We observe well-defined QWR formation only in the presence of thin GaAs capping of the elongated islands before annealing. Without thin GaAs capping, the In composition becomes too low for controlling the nucleation of (In,Ga)As islands in subsequent layers, necessary for QWR formation. Hence, thin GaAs capping is crucial to reproducibly balance In desorption for formation and vertical correlation of well-defined QWRs, serving as unique template for one-dimensional quantum dot ordering. (C) 2002 Elsevier Science B.V. All rights reserved.