  We report the growth of InAs$_{1-x}$Sb$_{x}$ nanowires ($0\leq x \leq 0.15$)
grown by catalyst-free molecular beam epitaxy on silicon (111) substrates. We
observed a sharp decrease of stacking fault density in the InAs$_{1-x}$Sb$_{x}$
nanowire crystal structure with increasing antimony content. This decrease
leads to a significant increase in the field-effect mobility, this being more
than three times greater at room temperature for InAs$_{0.85}$Sb$_{0.15}$
nanowires than InAs nanowires.
