Selectivity Map for Molecular Beam Epitaxy of Advanced III–V Quantum Nanowire Networks

Abstract

Selective-area growth is a promising technique for enabling of the fabrication of the scalable III–V nanowire networks required to test proposals for Majorana-based quantum computing devices. However, the contours of the growth parameter window resulting in selective growth remain undefined. Herein, we present a set of experimental techniques that unambiguously establish the parameter space window resulting in selective III–V nanowire networks growth by molecular beam epitaxy. Selectivity maps are constructed for both GaAs and InAs compounds based on in situ characterization of growth kinetics on GaAs(001) substrates, where the difference in group III adatom desorption rates between the III–V surface and the amorphous mask area is identified as the primary mechanism governing selectivity. The broad applicability of this method is demonstrated by the successful realization of high-quality InAs and GaAs nanowire networks on GaAs, InP, and InAs substrates of both (001) and (111)B orientations as well as homoepitaxial InSb nanowire networks. Finally, phase coherence in Aharonov–Bohm ring experiments validates the potential of these crystals for nanoelectronics and quantum transport applications. This work should enable faster and better nanoscale crystal engineering over a range of compound semiconductors for improved device performance.

Growth of nanowire arrays from micron-feature templates

“…different substrate preparation. It was confirmed though that the Ga droplets on the mask do not affect the NW growth [50][51][52]. A magnified tilted AFM image of a single nanohole shows that the Ga droplets are centered inside their holes ( figure 3(b)) and exhibit a high contact angle (higher than 85°).…”

GaAs nanoscale membranes: prospects for seamless integration of III–Vs on silicon

“…We observe that GaAs grows only in the longitudinal openings in the SiO 2 mask with a high degree of selectivity, as reported for GaAs substrates. 39,41,46 Compared to the growth on GaAs substrates, 41 the NMs grown on Si do not completely fill the openings for longer slits, as seen in Fig. 1(c).…”

“…37,38 SAE is carried out on nanopatterned substrates at high temperature in such a way that the sticking coefficient of the adatoms is zero on the mask and non-zero in the etched openings. 39 The growth of GaAs nanomembranes (NMs) on GaAs (111)B substrates has been achieved by etching long slits along the 〈112〉 family of directions, as reported for both metalorganic chemical vapour deposition (MOCVD) 40 and molecular beam epitaxy (MBE). 41 The shape of these NMs is primarily driven by the growth kinetics.…”

In-plane selective area InSb–Al nanowire quantum networks

“…A more scalable approach, would be to use an in-plane selective area growth (SAG) technique (i.e., parallel to the substrate surface), that relies on a template or mask to selectively grow one semiconductor material on top of another [13][14][15][16][17][18][19] . This technique has several advantages over out-of-plane growth.…”

“…Furthermore, the disorder created by the lattice mismatch can be detrimental to the topological protection of Majorana states 23 . 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 .…”