After CMP and before an epitaxial growth step, the substrate is prepared by an atmospheric plasma which includes not only a reducing chemistry, but also metastable states of a chemically inert carrier gas. This removes residues, oxides, and/or contaminants. Optionally, nitrogen passivation is also performed under atmospheric conditions, to passivate the substrate surface for later epitaxial growth.

A method of performing HVPE heteroepitaxy comprises exposing a substrate to a carrier gas, a first precursor gas, a Group II/III element, and ternary-forming gasses (V/VI group precursor), to form a heteroepitaxial growth of a binary, ternary, and/or quaternary compound on the substrate; wherein the carrier gas is H.sub.2, wherein the first precursor gas is HCl, the Group II/III element comprises at least one of Zn, Cd, Hg, Al, Ga, and In; and wherein the ternary-forming gasses comprise at least two or more of AsH.sub.3 (arsine), PH.sub.3 (phosphine), H.sub.2Se (hydrogen selenide), H.sub.2Te (hydrogen telluride), SbH.sub.3 (hydrogen antimonide, or antimony tri-hydride, or stibine), H.sub.2S (hydrogen sulfide), NH.sub.3 (ammonia), and HF (hydrogen fluoride); flowing the carrier gas over the Group II/III element; exposing the substrate to the ternary-forming gasses in a predetermined ratio of first ternary-forming gas to second ternary-forming gas (1tf:2tf ratio); and changing the 1tf:2tf ratio over time.

In one example of the disclosed technology, a method of fabricating a device comprises forming a patterned layer of a material on a surface of a substrate by depositing the material through a stencil mask, and forming a passivating layer over the patterned layer and the substrate surface in a sealed apparatus, the substrate being maintained under a vacuum until after the passivating layer has been formed. In some examples, the passivation is performed by oxidising a deposited aluminium layer within a deposition chamber. In some examples, the method can be used for fabricating hybrid semiconductor-superconductor devices, such as Majorana zero mode (MZM) nanowire structures for topological quantum bits.

A method for producing a semiconductor element includes a step of forming a multiple quantum well in which a GaSb layer and an InAs layer are alternately stacked on a GaSb substrate by MOVPE, wherein, in the step of forming a multiple quantum well, an InSb film is formed on at least one of a lower-surface side and an upper-surface side of the InAs layer so as to be in contact with the InAs layer.

After CMP and before an epitaxial growth step, the substrate is prepared by an atmospheric plasma which includes not only a reducing chemistry, but also metastable states of a chemically inert carrier gas. This removes residues, oxides, and/or contaminants. Optionally, nitrogen passivation is also performed under atmospheric conditions, to passivate the substrate surface for later epitaxial growth.