The appearance of InAs quantum-wire-like morphology on an AlInAs buffer layer grown by molecular-beam epitaxy on nominal InP(001) surfaces is investigated. Lateral composition modulation in the AlInAs buffer layer is suggested to play an important role in the formation of InAs nanowires. For InAs/AlInAs nanowire superlattices. the InAs nanowires are laterally correlated with respect to growth directions. By changing the spacer thickness, no evidence of vertical correlation is observed. The lack of vertical correlation is ascribed to the asymmetrical cross-sectional shape of the nanowires.