Full zinc-blende structure GaAs nanowire grown by a catalyst-free method is reported with As pulse injection in the initial growth time. When As is injected by a pulse while maintaining Ga injection, high Ga supersaturation could easily form nanowire nucleation for the seed formation. Then, continuous GaAs injection contributes to GaAs nanowire growth for increasing length. The GaAs nanowire could grow further with 3.7-mu m length and 120-nm diameter. GaAs nanowires were measured by transmission electron microscopy analysis. (C) 2013 Elsevier B.V. All rights reserved.