The incorporation of In in the growth of crescent-shaped In0.12Ga0.88As quantum wires embedded in (AlAs)(4)(GaAs)(8) superlattice barriers is studied in atomic detail using cross-sectional scanning tunneling microscopy. It is found that the In distribution in both the surface and the first subsurface layer can be atomically resolved in the empty- and filled-state images, respectively. Strong In segregation is seen at the InGaAs/GaAs interfaces, but neither an expected enhancement of the In concentration at the center of the quantum wire compared to the planar quantum well nor In clustering beyond the statistical expectation is observed. (C) 1995 American Institute of Physics.