We report the analysis of lateral composition modulation in (InAs) m /(GaSb) m superlattices by x-ray diffraction. Vertical and lateral satellite peaks for a 140 period structure were observed. The lateral modulation wavelength, average superlattice composition, and vertical superlattice wavelength were determined. The lateral modulation was observed only along one in-plane direction resulting in quantum wire-like structures along the ͓110͔ direction. The unconventional structure of the lateral composition modulation, in which the stacking of the layers leads to a doubling of the vertical superlattice period, is discussed.