The influence of the droplet composition on the vapor-liquid-solid growth of InAs nanowires on GaAs ((1)over-bar(1)over-bar(1)over-bar)B by metal-organic vapor phase epitaxy

The heteroepitaxial growth of InAs nanowires (NWs) ((1) over bar(1) over bar(1) over bar)(B) on GaAs substrate was investigated by metal-organic vapor phase epitaxy. The vapor-liquid-solid (VLS) growth mechanism was applied with gold as seed material. InAs NW with two types of morphology were observed. The first morphology type exhibited a tapered NW shape. In a distinct region below the alloy particle the shape was influenced by the precursor surface diffusion. The NW growth was attributed to Au-rich liquid alloy particles containing gallium as a result of the initial Au-GaAs interaction. Differential scanning calorimetry measurements revealed the lowest eutectic temperature of the Au-Ga-In liquid alloy for different compositions. For a considerable amount of gallium inside the ternary alloy, the eutectic temperature was found to be below the InAs NW growth temperature window. A second type of morphology with a more columnlike shape was related to a very high indium fraction inside the liquid alloy particle during VLS growth. These NW exhibited a change in the side facet orientation from {(2) over bar 11} to {(1) over bar 10} below the droplet. Additionally, the sample structure was studied by transmission electron microscopy. A change in the InAs NW crystal structure from sphalerite-type to mainly wurtzite-type was observed with an increase in the growth temperature. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3033556]