We report on he growth of single crystal InAs nanowires on Si/SiOx substrates by chemical vapor deposition (CVD). Both pure zincblende InAs nanowires and twin superlattice InAs nanowires are produced. We demonstrate that the morphology and crystal structure of these nanowires can be controlled by tuning the H-2 carrier gas How rate in a CVD furnace and show that highly selected growth of twin superlattice nanowires are achieved at high carrier gas How rates. Our work provides a new route to grow and phase-engineer single crystal InAs nanowires for a wide range of potential applications. (C) 2015 Elsevier B.V. All rights reserved.