Semiconductor-superconductor hybrid device and its fabrication
A method of fabricating a semiconductor-superconductor hybrid device comprises providing a workpiece comprising a semiconductor component, a layer of a first superconductor material on the semiconductor component, and a layer of a second superconductor material on the first superconductor material, the second superconductor material being different from the first superconductor material; etching the layer of the second superconductor material to expose a portion of the first superconductor material; and oxidising the portion of the first superconductor material to form a passivating layer on the semiconductor. The first superconductor provides energy coupling between the semiconductor and the second superconductor, and the passivating layer protects the semiconductor while allowing electrostatic access thereto. Also provided are a hybrid device, and a method of etching.
1. A method of fabricating a semiconductor-superconductor hybrid device, which method comprises:
providing a workpiece comprising a semiconductor component, a layer of a first superconductor material on the semiconductor component, and a layer of a second superconductor material on the layer of first superconductor material, the second superconductor material being different from the first superconductor material;
etching the layer of the second superconductor material to expose a portion of the first superconductor material; and
oxidising the portion of the first superconductor material to form a passivating layer on the semiconductor component.
2. The method according to claim 1 , wherein the first superconductor material is aluminium.
3. The method according to claim 1 , wherein the layer of the first superconductor material has a thickness of less than or equal to 3 nm.
4. The method according to claim 1 , wherein the second superconductor material is selected from lead, indium, vanadium, tantalum, tin, rhenium and niobium.
5. The method according to claim 4 , wherein the second superconductor material is lead.
6. The method according to claim 5 , wherein the etching comprises contacting the second superconductor material with an etchant composition comprising an acid selected from nitric acid and acetic acid.
7. The method according to claim 6 , wherein the acid is acetic acid; wherein etchant composition further comprises propan-2-ol; and wherein the concentration of the acetic acid in the etchant composition is 5% to 20% by volume.
8. The method according to claim 4 , wherein the second superconductor material is niobium, and wherein the etching comprises reactive ion etching using chloride ions.
9. The method according to claim 1 , which is performed at a temperature less than or equal to 0° C.
10. The method according to claim 1 , further comprising, before the etching:
forming a layer of resist on the layer of second superconductor material;
selectively exposing the layer of resist; and
developing the resist to form a mask on the layer of second superconductor material.
11. The method according to claim 1 , further comprising fabricating a gate electrode for applying an electrostatic field to the semiconductor component.