Disclosed are methods and mask structures for epitaxially growing substantially defect-free semiconductor material. In some embodiments, mask structure includes a first level defining a first trench extending through the first level, wherein a bottom of the first trench is defined by a semiconductor substrate, and a second level on top of the first level, wherein the second level defines a plurality of second trenches positioned at a non-zero angle with respect to the first trench.

A strip of sacrificial semiconductor material is formed on top of a non-sacrificial semiconductor material substrate layer. A conformal layer of the non-sacrificial semiconductor material is epitaxially grown to cover the substrate layer and the strip of sacrificial semiconductor material. An etch is performed to selectively remove the strip of sacrificial semiconductor material and leave a hollow channel surrounded by the conformal layer and the substrate layer. Using an anneal, the conformal layer and the substrate layer are reflowed to produce an optical waveguide structure including the hollow channel.

A strip of sacrificial semiconductor material is formed on top of a non-sacrificial semiconductor material substrate layer. A conformal layer of the non-sacrificial semiconductor material is epitaxially grown to cover the substrate layer and the strip of sacrificial semiconductor material. An etch is performed to selectively remove the strip of sacrificial semiconductor material and leave a hollow channel surrounded by the conformal layer and the substrate layer. Using an anneal, the conformal layer and the substrate layer are reflowed to produce an optical waveguide structure including the hollow channel.

Various examples related to metaconductor based skins and transmission lines are provided. In one example, a flexible metaconductor skin includes a flexible substrate; at least one layer of non-ferromagnetic metal disposed on the flexible substrate; and a layer of ferromagnetic metal disposed on the at least one layer of non-ferromagnetic metal. The flexible metaconductor skin can be used as a multi-layer coplanar waveguide (CPW) transmission line.

A nucleation structure for the epitaxial growth of three-dimensional semiconductor elements, including a substrate including a monocrystalline material forming a growth surface, a plurality of intermediate portions made of an intermediate crystalline material epitaxied from the growth surface and defining an upper intermediate surface, and a plurality of nucleation portions, made of a material including a transition metal forming a nucleation crystalline material, each epitaxied from the upper intermediate surface, and defining a nucleation surface suitable for the epitaxial growth of a three-dimensional semiconductor element.

A nucleation structure for the epitaxial growth of three-dimensional semiconductor elements, including a substrate including a monocrystalline material forming a growth surface, a plurality of intermediate portions made of an intermediate crystalline material epitaxied from the growth surface and defining an upper intermediate surface, and a plurality of nucleation portions, made of a material including a transition metal forming a nucleation crystalline material, each epitaxied from the upper intermediate surface, and defining a nucleation surface suitable for the epitaxial growth of a three-dimensional semiconductor element.

In one instance, the seed crystal of this invention provides a nitrogen-polar c-plane surface of a GaN layer supported by a metallic plate. The coefficient of thermal expansion of the metallic plate matches that of GaN layer. The GaN layer is bonded to the metallic plate with bonding metal. The bonding metal not only bonds the GaN layer to the metallic plate but also covers the entire surface of the metallic plate to prevent corrosion of the metallic plate and optionally spontaneous nucleation of GaN on the metallic plate during the bulk GaN growth in supercritical ammonia. The bonding metal is compatible with the corrosive environment of ammonothermal growth.

In one instance, the seed crystal of this invention provides a nitrogen-polar c-plane surface of a GaN layer supported by a metallic plate. The coefficient of thermal expansion of the metallic plate matches that of GaN layer. The GaN layer is bonded to the metallic plate with bonding metal. The bonding metal not only bonds the GaN layer to the metallic plate but also covers the entire surface of the metallic plate to prevent corrosion of the metallic plate and optionally spontaneous nucleation of GaN on the metallic plate during the bulk GaN growth in supercritical ammonia. The bonding metal is compatible with the corrosive environment of ammonothermal growth.

The present disclosure relates to a device and method for forming efficient quantum devices, in particular quantum devices that have not been contaminated in ex-situ processes. In particular the presently disclosed method can be applied for manufacturing of a Josephson junction which is an element in a tunable superconducting qubit. One embodiment relates to a method for in-situ production of a barrier/gap in the surface layer(s) of an elongated nanostructure, the method comprising the steps of providing at least one elongated device nanostructure on a substrate in a vacuum chamber having at least one deposition source, providing at least one elongated shadow nanostructure in said vacuum chamber, and depositing at least a first facet layer on at least a part of the device nanostructure(s) and the shadow nanostructure(s) by means of said deposition source, wherein the deposition source, the device nanostructure and the shadow nanostructure during deposition are arranged such that the shadow nanostructure covers and forms a shadow mask on at least a part of the device nanostructure thereby forming a gap in the first facet layer deposited on the device nanostructure.

The present disclosure relates to a device and method for forming efficient quantum devices, in particular quantum devices that have not been contaminated in ex-situ processes. In particular the presently disclosed method can be applied for manufacturing of a Josephson junction which is an element in a tunable superconducting qubit. One embodiment relates to a method for in-situ production of a barrier/gap in the surface layer(s) of an elongated nanostructure, the method comprising the steps of providing at least one elongated device nanostructure on a substrate in a vacuum chamber having at least one deposition source, providing at least one elongated shadow nanostructure in said vacuum chamber, and depositing at least a first facet layer on at least a part of the device nanostructure(s) and the shadow nanostructure(s) by means of said deposition source, wherein the deposition source, the device nanostructure and the shadow nanostructure during deposition are arranged such that the shadow nanostructure covers and forms a shadow mask on at least a part of the device nanostructure thereby forming a gap in the first facet layer deposited on the device nanostructure.