We demonstrate the self-catalyst growth of vertically aligned InAs nanowires on bare Si(111) by droplet epitaxy. The growth conditions of indium droplets suitable for nucleation and growth of nanowires have been identified. We have then realized vertically aligned and non-tapered InAs nanowires on bare Si(111) substrates through optimal indium droplets. It was found that the lateral dimensions and density of nano-wires are defined by the indium droplets. This technique unravels a controllable, cost-effective and time-efficient route to fabricating functional monolithic hybrid structures of InAs nanowires on silicon.