Catalyst-assisted hydride vapor phase epitaxy of GaN nanowires: exceptional length and constant rod-like shape capability.

The hydride vapor phase epitaxy (HVPE) process exhibits unexpected properties when growing GaN semiconductor nanowires (NWs). With respect to the classical well-known methods such as metal organic vapor phase epitaxy and molecular beam epitaxy, this near-equilibrium process based on hot wall reactor technology enables the synthesis of nanowires with a constant cylinder shape over unusual length. Catalyst-assisted HVPE shows a record short time process (less than 20 min) coupled to very low precursor consumption. NWs are grown at a fast solidification rate (50 µm h(-1)), facilitated by the high decomposition frequency of the chloride molecules involved in the HVPE process as element III precursors. In this work growth temperature and V/III ratio were investigated to determine the growth mechanism which led to such long NWs. Analysis based on the Ni-Ga phase diagram and the growth kinetics of near-equilibrium HVPE is proposed.

Fast growth synthesis of GaAs nanowires with exceptional length.

We report the first synthesis of GaAs nanowires (NWs) by Au-assisted vapor-liquid-solid (VLS) growth in the novel hydride vapor phase epitaxy (HVPE) environment. Forty micrometer long rodlike <111> monocrystalline GaAs nanowires exhibiting a cubic zinc blende structure were grown in 15 min with a mean density of 10(6) cm(-2). The synthesis of such long figures in such a short duration could be explained by the growth physics of near-equilibrium HVPE. VLS-HVPE is mainly based on solidification after direct and continuous feeding of the arsenious and GaCl growth precursors through the Au-Ga liquid catalyst. Fast solidification (170 microm/h) is then assisted by the high decomposition frequency of GaCl. This predominant feeding through the liquid-solid interface with no mass and kinetic hindrance favors axial rather than radial growth, leading to twin-free nanowires with a constant cylinder shape over unusual length. The achievement of GaAs NWs several tens of micrometers long showing a high surface to volume ratio may open the field of III-V wires, as already addressed with ultralong Si nanowires.