Mobility Enhancement by Sb-mediated Minimisation of Stacking Fault Density in InAs Nanowires Grown on Silicon

Abstract

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...

Tuning growth direction of catalyst-free InAs(Sb) nanowires with indium droplets

“…However, a challenge remains concerning the presence of stacking defects in self-catalyzed InAs nanowires [14,15]. One pathway towards defect-free crystals is the growth of ternary nanowires, as recently demonstrated by the growth of InAs 1−x Sb x nanowires [16,17]. Another approach to obtain defect-free nanowires would include a change of polarity [18] or growth direction [19], since the typical stacking defects observed in III-V nanowires are related to the formation of {111}B planes [20].…”

Observation of coherent electron transport in self-catalysed InAs and InAs1–xSbx nanowires grown on silicon

“…The study of coherent electron transport was performed on InAs and InAs 0.85 Sb 0.15 nanowires grown by molecular beam epitaxy via a catalyst-free process, as described in a previous work [16]. Table I shows the average dimensions and electrical characteristics (extracted from field-effect measurements [16]) of the studied groups of nanowires.…”

“…Table I shows the average dimensions and electrical characteristics (extracted from field-effect measurements [16]) of the studied groups of nanowires. The mobility of the InAs 0.85 Sb 0.15 nanowires is significantly higher than that of the InAs nanowires.…”

“…Conversely, the InAs nanowires present a higher carrier concentration. The distribution of polytypes and defects in the nanowires was quantified through high-resolution TEM [16]. The InAs nanowires exhibit a mixture of wurtzite and zincblende structures with a dominant wurtzite polytype (83% of wurtzite polytype on average) and a high density of stacking faults (SF): 360 SF per micrometer.…”

“…uncontrolled axial modulation of the crystal structure between the zinc-blende (cubic) and the wurtzite (hexagonal) polytypes [2,6], which in turn leads to a reduction of the electron mobility [15]. In a previous work, we investigated an approach to reduce the defect density in catalyst-free InAs nanowires via the incorporation of antimony during the growth [16]. The antimony incorporation suppresses the hexagonal phase and reduces the stacking fault density by up to one order of magnitude, resulting in a large increase in the electron mobility above that of pure InAs nanowires.…”