For application in novel opto-electronic nanowire devices, Ga-assisted GaAs/In(x)Ga(1-x)As axial heterostructure nanowires grown on a (1 1 1)Si substrate at a high In/Ga flux ratio were investigated. The increased diameter of the In(x)Ga(1-x)As region of the nanowire was observed from a scanning electron microscopy image. The In composition of 0.01-0.02 of the In(x)Ga(1-x)As was shown by EDX point analysis. The In concentration of 0.62 of an In-Ga alloy droplet was estimated from the diameter ratio of the In(x)Ga(1-x)As region. From these results, it was considered that the excess In was collected in the droplet, resulting in an increased nanowire diameter. The increased diameter of the In(x)Ga(1-x)As region was also discussed together with the results of thermodynamic calculation. (C) 2010 Elsevier B.V. All rights reserved.