Method of fabricating a semiconductor device
A semiconductor device is fabricated by: forming a shadow wall on a substrate; subsequently growing a nanowire of semiconductor material on the substrate; and directionally depositing a layer of a further material on the nanowire from a direction selected such that the shadow wall casts a shadow on the nanowire, the shadow being a region in which the further material is not deposited. The nanowire is vertically orientated relative to the substrate. The shadow wall comprises a base portion and a bridge portion. The bridge portion overhangs the substrate and is supported by the base portion. Patterning of the further material may be achieved without the use of etching, thereby avoiding damage to the semiconductor. Also provided is a semiconductor-superconductor hybrid device; a quantum computing device comprising the semiconductor-superconductor hybrid device; and a shadow wall for controlling directional deposition of a material.
1 . A method of fabricating a semiconductor device on a substrate, which method comprises:
forming a shadow wall on the substrate;
subsequently growing a nanowire of semiconductor material on the substrate; and
directionally depositing a layer of a further material on the nanowire from a direction selected such that the shadow wall casts a shadow on the nanowire, the shadow being a region in which the further material is not deposited;
wherein the nanowire is vertically orientated with respect to the substrate;
wherein the shadow wall comprises a base portion and a bridge portion, wherein the bridge portion overhangs the substrate, and the base portion supports the bridge portion; and
further wherein:
the bridge portion is configured to cast a shadow on two or more facets of the nanowire; or
the directional deposition forms a full shell of the further material around an unshadowed portion of the nanowire.
2 . The method according to claim 1 , wherein the substrate is planar.
3 . The method according to claim 1 , wherein the nanowire is grown by a vapour-liquid-solid process.
4 . The method according to claim 1 , wherein the nanowire is grown by a templated growth process.
5 . The method according to claim 1 , wherein the bridge portion is ring-shaped in plan, and wherein the nanowire is grown at the center of the ring shape.
6 . The method according to claim 1 , wherein the shadow wall is a first shadow wall, and a plurality of shadow walls, including the first shadow wall, are formed.
7 . The method according to claim 1 , wherein, after forming the shadow wall, no etching is performed.
8 . A semiconductor-superconductor hybrid device, comprising:
a planar substrate;
a nanowire of semiconductor material having a length, the nanowire extending vertically from the planar substrate; and
first and second superconductor components capable of undergoing energy level hybridisation with the semiconductor material;
wherein the first superconductor component is arranged on a lower portion of the length of the nanowire;
wherein the second superconductor component is arranged on an upper portion of the length of the nanowire;
wherein the first and second superconductor components are vertically spaced from one another, defining a junction portion of the nanowire; and
wherein at least one of the first and second superconductor components is in a form of a full shell surrounding the nanowire.
9 . The semiconductor-superconductor hybrid device according to claim 8 , further comprising a shadow wall in turn comprising a bridge portion, which overhangs the planar substrate, and a base portion supporting the bridge portion.
10 . The semiconductor-superconductor hybrid device according to claim 9 , wherein the bridge portion is ring-shaped in plan, and surrounds the nanowire.
11 . The semiconductor-superconductor hybrid device according to claim 8 , further comprising a gate electrode for gating the junction portion.
12 . The semiconductor-superconductor hybrid device according to claim 8 , further comprising a dielectric filler for supporting the nanowire.
13 . The semiconductor-superconductor hybrid device according to claim 8 , wherein the at least one of the first superconductor component or the second superconductor component comprises aluminum, niobium, lead, indium, or tin.
14 . A method of fabricating a semiconductor device on a substrate, which method comprises:
forming a shadow wall on the substrate;
subsequently growing a nanowire of semiconductor material on the substrate;
directionally depositing a layer of a further material on the nanowire from a direction selected such that the shadow wall casts a shadow on the nanowire, the shadow being a region in which the further material is not deposited; and
after directionally depositing the layer of the further material, removing the shadow wall;
wherein the nanowire is vertically orientated with respect to the substrate; and
wherein the shadow wall comprises a base portion and a bridge portion, wherein the bridge portion overhangs the substrate and the base portion supports the bridge portion.
15 . The method according to claim 14 , wherein the further material is selected from the group consisting of a superconductor material, a metal, and a ferromagnetic insulator material.
16 . The method according to claim 14 , wherein the further material comprises a superconductor material, which is selected from the group consisting of aluminum, niobium, lead, indium, and tin.
17 . The method according to claim 14 , further comprising, after forming the shadow wall, maintaining the substrate in a vacuum until after the directional deposition.
18 . The method of claim 14 , wherein growing the nanowire is performed using a vapour-liquid-solid process, or using a templated growth process.
19 . A semiconductor-superconductor hybrid device, comprising:
a shadow wall formed on a substrate;
a nanowire of semiconductor material formed on the substrate, the nanowire being vertically orientated with respect to the substrate; and
a layer of a further material on the nanowire adjacent to a shadow region in which the further material is not deposited, the shadow region defined as a shadow of the shadow wall on the nanowire along a deposition direction;
wherein the shadow wall comprises a base portion and a bridge portion, wherein the bridge portion overhangs the substrate, the base portion supports the bridge portion, and the shadow region lies over two or more facets of the nanowire.
20 . The semiconductor-superconductor hybrid device according to claim 19 , wherein the bridge portion includes a notch and/or a protrusion.
21 . The semiconductor-superconductor hybrid device of claim 19 , wherein the substrate is planar.
22 . The semiconductor-superconductor hybrid device of claim 19 , wherein the bridge portion of the shadow wall comprises a notch.
23 . The semiconductor-superconductor hybrid device of claim 19 , wherein the bridge portion of the shadow wall comprises a protrusion.
24 . The semiconductor-superconductor hybrid device of claim 19 , wherein the layer of further material is a full shell around the nanowire.
25 . The semiconductor-superconductor hybrid device of claim 19 , wherein the semiconductor material comprises a III-V material.
26 . The semiconductor-superconductor hybrid device of claim 19 , wherein the semiconductor material comprises a II-VI material.