Ballistic InSb Nanowires and Networks via Metal-Sown Selective Area Growth

Abstract

Selective area growth is a promising technique to realize semiconductorsuperconductor hybrid nanowire networks potentially hosting topologically protected Majorana-based qubits. In some cases, however, such as molecular beam epitaxy of InSb on InP or GaAs substrates, nucleation and selective growth conditions do not necessarily overlap. To overcome this challenge we propose Metal-Sown Selective Area Growth (MS SAG) technique which allows decoupling selective deposition and nucleation growth conditions by temporarily isolating these stages. It consists of three steps: (i) selective deposition of In droplets only inside the mask openings at relatively high temperatures favoring selectivity, (ii) nucleation of InSb under Sb flux from In droplets which act as a reservoir of group III adatoms, done at relatively low temperatures favoring nucleation of InSb, (iii) homoepitaxy of InSb on top of formed nucleation Page 3 of 43 ACS Paragon Plus Environment Nano Letters layer under simultaneous supply of In and Sb fluxes at conditions favoring selectivity and high crystal quality. We demonstrate that complex InSb nanowire networks of high crystal and electrical quality can be achieved this way. We extract mobility values of 10,000-25,000 cm V-1 s-1 consistently from field-effect and Hall mobility measurements across single nanowire segments as well as wires with junctions. Moreover, we demonstrate ballistic transport in a 440 nm long channel in a single nanowire under magnetic field below 1 T. We also extract a phase-coherent length of ~8 µm at 50 mK in mesoscopic rings. Semiconductor-superconductor hybrid nanowire (NW) networks are promising candidates for hosting topologically protected Majorana-based qubits, which have a potential to revolutionize the emerging field of quantum computing. 1 The III-V semiconductor InSb is of particular interest in this regard owing to its large g-factor, which enables a relatively small magnetic field to drive a hybrid semiconductor-superconductor NW into the topological regime. Moreover the small effective mass favorably leads to a large subband spacing. 2 So far, mostly single 3 or small-scale networks 4 of InSb NWs were used in Majorana-related transport experiments. To support further progress in the field,

In-plane selective area InSb–Al nanowire quantum networks

“…These defects may act as scattering sites for electrons and can be found in many reported SAG studies 13,17,19,27 . Therefore, it is important to enable growth of a complete, in-plane network structure from a single nucleation site, which is difficult to achieve for MBE-grown InSb 18,24 . For this, a large surface diffusion length of the precursor material is required, as well as a low nucleation probability.…”

“…Most of the previous SAG studies have focused on an InAs-based material system for nanowire networks [14][15][16][17]19 , which has a smaller lattice mismatch with InP or GaAs substrates. InSb nanowires have been grown by SAG using molecular beam epitaxy (MBE) 18,24 . Here, we demonstrate an in-plane SAG technique for scalable and high-quality InSb nanowire networks, which shows all the relevant quantum transport properties (e.g., long coherence length and excellentinduced superconducting properties) necessary for topological qubits.…”

Understanding Shape Evolution and Phase Transition in InP Nanostructures Grown by Selective Area Epitaxy

“…[ 10,27,28 ] More recently, complex III–V networks grown by SAE technique are extensively investigated because of their great potential in quantum science. [ 20,30–34 ] All these works show the significance of shape engineering in fundamental research and device applications from diverse perspectives.…”

Multiterminal Quantized Conductance in InSb Nanocrosses

“…[7,8] In addition, proposals for realizing quantum operations by braiding the world lines of non-abelian Majorana quasi-particles in networks of 1D hybrid nanowires [9] create a need to extend the conventional linear NW platform toward branched hybrid structures. Different schemes are being developed toward planar NW networks [10][11][12][13][14] and vapor-liquid-solid the amount of radial growth when the NW reach to it's final diameter d(t f ). For Δy < d Au the NWs meet "head-to-head" and the axial growth is interrupted preventing the formation of four-terminal crosses.…”

“…[ 7,8 ] In addition, proposals for realizing quantum operations by braiding the world lines of non‐abelian Majorana quasi‐particles in networks of 1D hybrid nanowires [ 9 ] create a need to extend the conventional linear NW platform toward branched hybrid structures. Different schemes are being developed toward planar NW networks [ 10–14 ] and vapor–liquid–solid NW growth has been extended to simpler branched structures either by changing the growth directions during growth [ 15–19 ] or by merging non‐parallel NWs grown from tilted substrate facets. [ 20,21 ] The high mobility and strong SOI make indium antimonide (InSb) the optimal candidate for transport measurements, however, branched InSb NW structures and nanocrosses (NCs) have not so far been reported using molecular beam epitaxy (MBE) – traditionally leading to crystals with the lowest impurity concentration.…”