Growth of GaAs nanowires by self-assisted VLS-MBE

We can grow GaAs nanowires with a pure zinc blende structure and remarkable aspect ratios using gold-less self-assisted vapor-liquid-solid growth on (111) Si substrates in a molecular beam epitaxy system. Nanowires diameters all the way down to 20 nm can be obtained using a thin native oxide layer on the Si substrates. A remarkable uniformity in diameter and length can be achieved for nanowires exceeding ten microns. The structural phase distribution along the wire length is controlled by the effective V/III ratio and temperature at the growth interface. In particular, pure twin plane free nanowires having the zinc blende structure can be grown nicely spread out on the growth surface, with minimal bulk growth between the nanowires. The low density of nanowires that can be achieved has been successfully used to for growth of GaAs nanowires embedded in an AlAs/GaAs shell.
This study has been carried out in collaboration with Peter Krogstrup at the Nano-Science Center, Niels Bohr Institute, University of Copenhagen, Denmark.