Zn-doping of GaAs nanowires grown by Aerotaxy

Nanowires were grown by means of a novel aerosol-based method called Aerotaxy. Here an aerosol of Au catalyst nanoparticles in N2 is mixed with MOVPE precursors in a flow-through reactor at atmospheric pressure, whereby nanowires are produced continuously in high concentrations. We demonstrate the possibility of in situ doping of the NWs and the realization of well-controlled p-type GaAs nanowires using this Aerotaxy method. By controlling the cracking and concentration of the precursors, p-doped GaAs nanowires could be grown exhibiting a wide range of Zn doping levels. DEZn was used as the dopant source and the injected DEZn/TMGa ratio was varied from 0.1% to 3.4%. The morphology, the crystalline structure and the composition of the nanowires were studied using SEM, TEM and XEDS. The nanowires were grown straight without any significant tapering and this ideal morphology could be maintained up to an injected DEZn/TMGa ratio of 3.4%. The nanowires typically grew in the 〈111〉 direction with a pure zincblende structure, but by increasing the DEZn flow the number of twinning defects increased which we ascribe to Zn incorporation. Elemental analysis shows a high Zn content in the catalyst particle and also a gradient in the Zn content along the nanowire. The samples were analyzed optically using photoluminescence (PL). From the result we estimated the free hole concentration induced by Zn acceptors to be 1×1020 cm−3 for DEZn/TMGa ratio of 3.4%. To our knowledge this is the first report on in situ doping of GaAs nanowires grown by Aerotaxy.