Semiconductor wafer with a layer of Al

1. A semiconductor wafer comprising the following layers in the given order:

a) a monocrystalline substrate wafer consisting essentially of silicon and having a (111) surface orientation,

c) a monocrystalline layer of Sc 2 O 3 having a (111) surface orientation,

d) a monocrystalline layer of ScN having a (111) surface orientation, and

f) a monocrystalline layer of Al z Ga 1-z N with 0≦z≦1 having a (0001) surface orientation.

2. The semiconductor wafer of claim 1 , further comprising b), a monocrystalline metal oxide layer between the substrate wafer and the layer of Sc 2 O 3 .

3. The semiconductor wafer of claim 2 , wherein the metal oxide layer has a cubic Ia-3 crystal structure and a composition of (M 1 w M 2 1-w ) 2 O 3 with 0≦w≦1, wherein M 1 is a first metal and M 2 is a second metal, wherein the metal oxide layer is located between the substrate wafer and the layer of Sc 2 O 3 , and wherein M 1 , M 2 and w are selected such that the lattice constant of the metal oxide layer is equal to or smaller than the lattice constant of the substrate wafer and equal to or larger than the lattice constant of the layer of Sc 2 O 3 .

4. The semiconductor wafer of claim 3 , wherein the layer of ScN has a thickness of 2 to 500 nm.

5. The semiconductor wafer of claim 1 , wherein the layer of Sc 2 O 3 has a thickness of 2 to 500 nm.

6. The semiconductor wafer of claim 2 , wherein the layer of Sc 2 O 3 has a thickness of 2 to 500 nm.

7. The semiconductor wafer of claim 1 , wherein the layer of ScN has a thickness of 2 to 500 nm.

8. The semiconductor wafer of claim 2 , wherein the layer of ScN has a thickness of 2 to 500 nm.

9. The semiconductor wafer of claim 1 , further comprising e), a monocrystalline metal nitride layer having a composition of (Al x Ga 1-x ) y Sc 1-y N with 0≦x≦1 and 0<y<1, the metal nitride layer being located between the layer of ScN and the layer of Al z Ga 1-z N.

10. The semiconductor wafer of claim 2 , further comprising e), a monocrystalline metal nitride layer having a composition of (Al x Ga 1-x ) y Sc 1-y N with 0≦x≦1 and 0<y<1, the metal nitride layer being located between the layer of ScN and the layer of Al z Ga 1-z N.

11. The semiconductor wafer of claim 1 , wherein z=0.

12. A process for the production of a semiconductor wafer of claim 1 , comprising the following steps in the given order:

a) providing a substrate wafer,

c) epitaxially depositing a layer of Sc 2 O 3 ,

d) producing a layer of ScN, and

f) epitaxially depositing a layer of Al z Ga 1-z N.

13. The process of claim 12 , wherein a monocrystalline metal oxide layer is epitaxially deposited in an additional step b) after step a) and prior to step c).

14. The process of claim 13 , wherein step c) is performed by means of CVD, MBE, PLD or sputtering techniques.

15. The process of claim 12 , wherein step c) is performed by means of CVD, MBE, PLD or sputtering techniques.

16. The process of claim 12 , wherein in step d) the layer of ScN is produced by converting a surface of the Sc 2 O 3 layer into ScN by exposing the surface to an atmosphere comprising a nitrogen source at a temperature of 200 to 1200° C.

17. The process of claim 12 , wherein in step d) the layer of ScN is produced by depositing a layer of Sc on the surface of the layer of Sc 2 O 3 and subsequently exposing the surface of the layer of Sc to an atmosphere comprising a nitrogen source at a temperature of 200 to 1200° C. and thus converting the layer of Sc into a layer of ScN.

18. The process of claim 12 , wherein in step d) the layer of ScN is produced by epitaxially depositing the layer of ScN on the surface of the layer of Sc 2 O 3 .

19. The process of claim 12 , wherein in a step e), a monocrystalline metal nitride layer having a composition of (Al x Ga 1-x ) y Sc 1-y N with 0≦x≦1 and 0<y<1 is epitaxially deposited after step d) and prior to step f).

20. The process of claim 12 , wherein step f) is performed by means of MOCVD or MBE.