We report the growth of InAs 1−x Sb x nanowires (0 ≤ x ≤ 0.15) grown by catalyst-free molecular beam epitaxy on silicon (111) substrates. We observed a sharp decrease of stacking fault density in the InAs 1−x Sb x nanowire crystal structure with increasing antimony content. This decrease leads to a significant increase in the field-effect mobility, this being more than three times greater at room temperature for InAs 0.85 Sb 0.15 nanowires than InAs nanowires. * To whom correspondence should be addressed † London Centre for Nanotechnology, University College London, London WC1H 0AH, United Kingdom ‡ Department of Electronic and Electrical Engineering, University College London, London WC1E 7JE, United Kingdom 1 arXiv:1402.3489v1 [cond-mat.mtrl-sci] Feb 2014Semiconductor nanowires are leading candidates for future applications in a wide variety of electronic, photonic and sensing devices. 1,2 III-V compound semiconductor nanowires including InAs 3 and GaN 4,5 have a number of potential functional advantages over elemental semiconductor nanowires including high mobility and direct bandgap. Furthermore the magnitude of the bandgap can be modulated by exploiting ternary compound semiconductors (such as InAsP 6 and AlGaAs 7 ), allowing the creation of heterostructure nanowires with axially-or radially-modulated electronic properties. Such bandgap engineering is in principle a more powerful tool for nanowire-based devices than thin-film-based devices since the radial relaxation of strain in nanowires allows the growth of heterostructures whose constituent compounds are significantly lattice-mismatched. 8,9 The growth of compound semiconductor nanowires directly onto single crystal silicon wafers would be advantageous, 10,11 because (i) it would allow integration of nanowire devices with the established silicon CMOS technology; and (ii) silicon wafers are orders of magnitude cheaper than their compound semiconductor counterparts. Compound semiconductor nanowires are, however, typically grown using the "vapor-liquid-solid" technique in which gold nanoparticle catalysts seed the growth. Gold cannot be combined with silicon since it forms trap states in the silicon bandgap. 12-14 Nickel has also been used to catalyze InAs nanowire growth on silicon 15 but these nanowires are not functional for direct integration as they grow following random orientations with respect to the substrate. There have therefore been many reports of nanowire growth without the use of heterocatalytic nanoparticle seeds [16][17][18][19][20][21] . In the case of the widely-studied narrow-bandgap semiconductor InAs, however, the absence of a heterocatalyst results in the nanowires displaying very high densities of defects including stacking faults, twin boundaries and polytypism, i.e. uncontrolled axial modulation of the crystal structure between the zinc-blende (cubic) and the wurtzite (hexagonal) polytypes of InAs. 17,21 This in turn leads to an undesirable suppression of the electron mobility. 22 In this letter, we investigate an approa...

We investigate different processes for optimizing the formation of Ohmic contacts to InAs nanowires. The nanowires are grown via molecular beam epitaxy without the use of metal catalysts. Metallic contacts are attached to the nanowires by using an electron beam lithography process. Before deposition of the contacts, the InAs nanowires are treated either by wet etching in an ammonium polysulfide (NH(4))(2)S(x) solution or by an argon milling process in order to remove a surface oxide layer. Two-point electrical measurements show that the resistance of the ammonium polysulfide-treated nanowires is two orders of magnitude lower than that of the untreated nanowires. The nanowires that are treated by the argon milling process show a resistance which is more than an order of magnitude lower than that of those treated with ammonium polysulfide. Four-point measurements allow us to extract an upper bound of 1.4 × 10(-7) Ω cm(2) for the contact resistivity of metallic contacts on nanowires treated by the argon milling process.

We report on the self-catalysed growth of vertical InAs(1-x)P(x) nanowires on Si(111) substrates by solid-source molecular-beam epitaxy. High-resolution transmission electron microscopy revealed the mixed wurtzite and zincblende structure of the nanowires. Energy dispersive x-ray spectroscopy and x-ray diffraction measurements were used to study the phosphorus content x in the InAs(1-x)P(x) nanowires, which was shown to be in the range 0-10 %. The dependence of phosphorus incorporation in the nanowires on the phosphorus flux in the growth chamber was investigated. The incorporation rate coefficients of As and P in InAs(1x)P(x) nanowires were found to be in the ratio 10 ± 5 to 1.