Advanced electronic device structures using semiconductor structures and superlattices

1. A set of semiconductor superlattices comprising:

a p-type or n-type first semiconductor superlattice comprising a plurality of unit cells each comprising at least two distinct layers formed of a substantially single crystal semiconductor, the p-type or n-type first semiconductor superlattice having a polar crystal structure with a growth axis being substantially parallel to a spontaneous polarization axis of the polar crystal structure, an average composition of the unit cells of the p-type or n-type first semiconductor superlattice exhibiting a monotonic change from an average composition corresponding to a wider band gap (WBG) material to an average composition corresponding to a narrower band gap (NBG) material or from an average composition corresponding to a NBG material to an average composition corresponding to a WBG material along the growth axis, which induces p-type or n-type conductivity;

a second semiconductor superlattice with a first constant average composition in the direction of the growth axis, wherein the second semiconductor superlattice is adjacent to a first side of the p-type or n-type first semiconductor superlattice in the direction of the growth axis; and

a third semiconductor superlattice with a second constant average composition in the direction of the growth axis, wherein the third semiconductor superlattice is adjacent to a second side of the p-type or n-type first semiconductor superlattice in the direction of the growth axis.

2. The set of semiconductor superlattices of claim 1 , wherein the p-type or n-type first semiconductor superlattice is p-type, and wherein:

the p-type semiconductor first superlattice comprises a cation-polar crystal structure and the average composition of the unit cells of the p-type first semiconductor superlattice changes monotonically from an average composition corresponding to a wider band gap (WBG) material to an average composition corresponding to a narrower band gap (NBG) material along the growth axis; or

the p-type first semiconductor superlattice comprises an anion-polar crystal structure and the average composition of the unit cells of the p-type first semiconductor superlattice changes monotonically from an average composition corresponding to a NBG material to an average composition corresponding to a WBG material along the growth axis.

3. The set of semiconductor superlattices of claim 2 , wherein:

the anion-polar crystal structure is a nitrogen-polar crystal structure or an oxygen-polar crystal structure; and

the cation-polar crystal structure is a metal-polar crystal structure.

4. The set of semiconductor superlattices of claim 1 , wherein the p-type or n-type first semiconductor superlattice is n-type, and wherein:

the n-type semiconductor first superlattice comprises a cation-polar crystal structure and the average composition of the unit cells changes monotonically from an average composition corresponding to a narrower band gap (NBG) material to an average composition corresponding to a wider band gap (WBG) material along the growth axis; or

the n-type first semiconductor superlattice comprises an anion-polar crystal structure and the average composition of the unit cells changes monotonically from an average composition corresponding to a WBG material to an average composition corresponding to a NBG material along the growth axis.

5. The set of semiconductor superlattices of claim 4 , wherein:

the cation-polar crystal structure is a metal-polar crystal structure; and

the anion-polar crystal structure is a nitrogen-polar crystal structure or an oxygen-polar crystal structure.

6. The set of semiconductor superlattices of claim 1 , wherein the average composition of the unit cells of the p-type or n-type first semiconductor superlattice is changed in a stepwise manner along the growth axis.

7. The set of semiconductor superlattices of claim 1 , wherein the average composition of the unit cells of the p-type or n-type first semiconductor superlattice is changed by changing a thickness of one or more of the at least two distinct layers of the unit cells.

8. The set of semiconductor superlattices of claim 1 , wherein a thickness of the unit cells of the p-type or n-type first semiconductor superlattice is constant along the growth axis.

9. The set of semiconductor superlattices of claim 1 , wherein a composition of one or more of the at least two distinct layers of the unit cells of the p-type or n-type first semiconductor superlattice is selected from the following:

gallium nitride (GaN);

aluminium nitride (AlN);

aluminium gallium nitride (AlxGa1-xN) where 0≤x≤1;

boron aluminium nitride BxAl1-xN where 0≤x≤1; and

aluminium gallium indium nitride (AlxGayIn1-x-yN) where 0≤x≤1, 0≤y≤1 and 0≤(x+y)≤1.

10. The set of semiconductor superlattices of claim 1 , wherein a composition of one or more of the at least two distinct layers of the unit cells of the p-type or n-type first semiconductor superlattice is selected from the following:

magnesium oxide (MgO);

zinc oxide (ZnO); and

magnesium zinc oxide (MgxZn1-xO) where 0≤x≤1.

11. The set of semiconductor superlattices of claim 1 , wherein the at least two distinct layers of each unit cell of the p-type or n-type first semiconductor superlattice each have a thickness that is less than the de Broglie wavelength of a charge carrier in the respective layer.

12. The set of semiconductor superlattices of claim 1 , wherein the at least two distinct layers of each unit cell of the p-type or n-type first semiconductor superlattice each have a thickness that is less than or equal to a critical layer thickness required to maintain elastic strain.

13. The set of semiconductor superlattices of claim 1 , wherein:

one or more of the at least two distinct layers of each unit cell of the p-type or n-type first semiconductor superlattice comprise impurity dopants to enhance the induced p-type or n-type conductivity.

14. The set of semiconductor superlattices of claim 1 , wherein the first constant average composition corresponds to the wider band gap (WBG) material.

15. The set of semiconductor superlattices of claim 1 , wherein the second constant average composition corresponds to the narrower band gap (NBG) material.

16. The set of semiconductor superlattices of claim 1 , wherein:

the first constant average composition corresponds to the wider band gap (WBG) material; and

the second constant average composition corresponds to the narrower band gap (NBG) material.

17. The set of semiconductor superlattices of claim 1 , wherein the first constant average composition corresponds to a material with a bandgap that is different than the bandgap of the wider band gap (WBG) material.

18. The set of semiconductor superlattices of claim 1 , wherein the second constant average composition corresponds to a material with a bandgap that is different than the bandgap of the narrower band gap (NBG) material.

19. The set of semiconductor superlattices of claim 1 , wherein:

the first constant average composition corresponds to a material with a bandgap that is different than the bandgap of the wider band gap (WBG) material; and

the second constant average composition corresponds to a material with a bandgap that is different than the narrower band gap (NBG) material.

20. The set of semiconductor superlattices of claim 1 , wherein:

the monotonic change from an average composition corresponding to a wider band gap (WBG) material to an average composition corresponding to a narrower band gap (NBG) material or from an average composition corresponding to a NBG material to an average composition corresponding to a WBG material along the growth axis in the p-type or n-type first semiconductor superlattice comprises a continuous or a stepwise change in the average composition of the unit cells along the growth axis.