Semiconductor layer structure

1. A method for producing a semiconductor layer structure, the method comprising:

providing a Si substrate comprising a top surface;

forming a first semiconductor layer on the substrate, the first semiconductor layer comprising a plurality of vertical nanowire structures, arranged perpendicularly to the top surface of the substrate, the first semiconductor layer comprising AlN,

epitaxially growing a second semiconductor layer which laterally and vertically encloses the plurality of vertical nanowire structures thereby encapsulating dislocations in shells around individual vertical nanowire structures, wherein the second semiconductor layer comprises Al x Ga 1-x N, wherein 0≤x≤0.95.

2. The method of claim 1 , wherein epitaxially growing the second semiconductor layer comprises epitaxially growing shells from the vertical nanowire structures in an M-direction of the wurtzite crystal structure.

3. The method of claim 2 , wherein shells from different individual vertical nanowire structures unite laterally into a thin-film that starts to grow in a C-direction of the wurtzite crystal structure for forming the second semiconductor layer.

4. The method of claim 1 , wherein forming the first semiconductor layer comprises:

depositing the first semiconductor layer on the substrate by one or more of:

physical vapor deposition, PVD,

chemical vapor deposition, CVD,

plasma-enhanced chemical vapor deposition, PECVD,

metalorganic chemical vapor deposition, MOCVD, and

metalorganic vapor-phase epitaxy, MOVPE; and

etching the plurality of vertical nanowire structures from the first semiconductor layer.

5. The method of claim 1 , wherein forming the first semiconductor layer comprises epitaxially forming the plurality of vertical nanowire structures.

6. The method of claim 1 , wherein the second semiconductor layer is made from GaN.

7. The method of claim 1 , further comprising depositing a third semiconductor layer on the second semiconductor layer, the third semiconductor layer comprising Al y Ga 1-y N, wherein 0≤y≤0.95.

8. The method of claim 7 , further comprising depositing a fourth semiconductor layer on said third semiconductor layer, the fourth semiconductor layer comprising GaN.

9. The method of claim 1 , wherein the top surface of the Si substrate has a Miller index of {111}.

10. The method of claim 1 , wherein forming the first semiconductor layer comprises forming the plurality of vertical nanowire structures such that they have a vertical length in the range of 50-500 nm.

11. The method of claim 1 , wherein forming the first semiconductor layer comprises forming the plurality of vertical nanowire structures such that they have a vertical length in the range of 150-250 nm.

12. The method of claim 1 , wherein forming the first semiconductor layer comprises forming the plurality of vertical nanowire structures such that they have a lateral diameter in the range of 5-50 nm.

13. The method of claim 1 , wherein forming the first semiconductor layer comprises forming the plurality of vertical nanowire structures such that they have a lateral diameter in the range of 10-30 nm.

14. The method of claim 1 , wherein forming the first semiconductor layer comprises forming the plurality of vertical nanowire structures such that they are arranged in a repeating array pattern.

15. The method of claim 14 , wherein the repeating array pattern is a hexagonal pattern, wherein a vertical nanowire structure has six equidistant closest other vertical nanowire structures.

16. The method of claim 14 , wherein the repeating array pattern is a square pattern, wherein a vertical nanowire structure has four equidistant closest other vertical nanowire structures.

17. The method of claim 1 , wherein a distance between individual vertical nanowire structure is in the range of 10-500 nm.

18. The method of claim 1 , wherein a distance between individual vertical nanowire structure is in the range of 50-200 nm.

19. The method of claim 1 , wherein growing the second semiconductor layer is made such that it covers top portions of the plurality of vertical nanowire structures.

20. A method for producing a high-electron-mobility transistor device, the method comprising:

producing a semiconductor layer structure by:

providing a Si substrate comprising a top surface,

forming a first semiconductor layer on the substrate, the first semiconductor layer comprising a plurality of vertical nanowire structures, arranged perpendicularly to the top surface of the substrate, the first semiconductor layer comprising AlN,

epitaxially growing a second semiconductor layer which laterally and vertically encloses the plurality of vertical nanowire structures thereby encapsulating dislocations in shells around individual vertical nanowire structures, wherein the second semiconductor layer comprises Al x Ga 1-x N, wherein 0≤x≤0.95,

depositing a third semiconductor layer on the second semiconductor layer, the third semiconductor layer comprising Al y Ga 1-y N, wherein 0≤y≤0.95, and

depositing a fourth semiconductor layer on said third semiconductor layer, the fourth semiconductor layer comprising GaN;

the method further comprising:

forming at least two trenches through the third and fourth semiconductor layers by etching away portions of said third and fourth semiconductor layers;

depositing a first metallic layer into the trenches and on the second semiconductor layer;

forming a metallic source contact and a metallic drain contact, in the trenches, by etching away portions of the first metallic layer;

forming an oxide layer on the source and drain contacts;

forming a gate trench through the oxide layer, between and separate from the at least two trenches through the third and fourth semiconductor layers, by etching away a portion of the oxide layer;

depositing a second metallic layer into the gate trench; and

forming a metallic gate contact, in the gate trench, by etching away portions of the second metallic layer.