We demonstrate high vertical yield InAs1-xSbx (0 < x ≤ 0.18) nanowire arrays grown on InP (111)B substrates by calalyst-free selective-area metal-organic chemical vapor deposition. High antimony composition is achieved by pulsing the arsenic flow to reduce the effective arsenic partial pressure while keeping the antimony partial pressure fixed. This increases the antimony vapor phase composition while allowing the antimony partial pressure to be kept low enough to avoid antimony condensation on the growth mask. InAsSb nanowire arrays show strong emission by photoluminescence at 77 K, covering a wavelength range of 3.77 – 5.08 μm. These results pave the way to engineering optical properties and enabling hybrid integration for nanoscale mid-wavelength infrared optical devices.