Ultrawide bandgap semiconductor devices including magnesium germanium oxides
Various forms of Mg x Ge 1-x O 2-x are disclosed, where the MgxGe 1-x O 2-x are epitaxial layers formed on a substrate comprising a substantially single crystal substrate material. The epitaxial layer of Mg x Ge 1-x O 2-x has a crystal symmetry compatible with the substrate material. Semiconductor structures and devices comprising the epitaxial layer of Mg x Ge 1-x O 2-x are disclosed, along with methods of making the epitaxial layers and semiconductor structures and devices.
1. A method of forming a semiconductor device, the method comprising:
providing a substrate comprising a substantially single crystal substrate material that has a crystal symmetry compatible with an epitaxial layer of Mg x Ge 1-x O 2-x ; and
co-depositing materials onto the substrate to form the epitaxial layer of Mg x Ge 1-x O 2-x , with x having a value of 0<x<1;
wherein the materials comprise at least two elements selected from Mg, Ge, and oxygen in accordance with the value of x, the Mg, Ge and oxygen being supplied by a Mg source, a Ge source, and an activated oxygen source, respectively; and
wherein the co-depositing comprises using a growth temperature of 400-500° C., and a flux ratio k of the Ge source to the Mg source (Φ Ge inc /Φ Mg inc ) of k=3 to 9.
2. The method of claim 1 , further comprising depositing a buffer layer between the substrate and the epitaxial layer of Mg x Ge 1-x O 2-x .
3. The method of claim 1 , wherein the co-depositing is performed using a molecular beam epitaxy process.
4. The method of claim 1 , wherein in the co-depositing, the epitaxial layer of Mg x Ge 1-x O 2-x self-assembles.
5. The method of claim 1 , wherein the Mg x Ge 1-x O 2-x is Mg 2 GeO 4 , wherein x=2/3.
6. The method of claim 1 , wherein the flux ratio k has a value from 3 to 7.5 and the Mg x Ge 1-x O 2-x is Mg 2 GeO 4 , wherein x=2/3.
7. The method of claim 1 , wherein the co-depositing comprises doping the epitaxial layer.
8. The method of claim 7 , wherein the doping comprises substituting a Ge site of a corresponding undoped Mg x Ge 1-x O 2-x crystal structure with Ga to result in a p-type conductivity.
9. The method of claim 7 , wherein the doping comprises substituting a Mg site of a corresponding undoped Mg x Ge 1-x O 2-x crystal structure with Ga to result in an n-type conductivity.
10. The method of claim 7 , wherein the doping comprises substituting a Ge site of a corresponding undoped Mg x Ge 1-x O 2-x crystal structure with Al to result in a p-type conductivity.
11. The method of claim 7 , wherein the doping comprises substituting a Mg site of a corresponding undoped Mg x Ge 1-x O 2-x crystal structure with Al to result in an n-type conductivity.
12. The method of claim 7 , wherein the doping comprises substituting a Ge site or a Mg site of a corresponding undoped Mg x Ge 1-x O 2-x crystal structure with Li + to result in an p-type conductivity.
13. The method of claim 7 , wherein the doping comprises substituting a Mg site of a corresponding undoped Mg x Ge 1-x O 2-x crystal structure with Ni + .
14. The method of claim 7 , wherein the doping comprises substituting an oxygen site of a corresponding undoped Mg x Ge 1-x O 2-x crystal structure with N 3+ .
15. The method of claim 7 , wherein the doping comprises:
placing a Ge atom in a first location that is occupied by Mg in a corresponding undoped Mg x Ge 1-x O 2-x unit cell structure; and
placing a Mg atom in a second location that is occupied by Ge in the corresponding undoped Mg x Ge 1-x O 2-x unit cell structure.
16. The method of claim 1 , further comprising forming the semiconductor device from the substrate and the epitaxial layer of Mg x Ge 1-x O 2-x .
17. A method of forming a semiconductor device, the method comprising:
providing a substrate comprising a substantially single crystal substrate material that has a crystal symmetry compatible with an epitaxial layer of Mg x Ge 1-x O 2-x ;
co-depositing materials onto the substrate to form the epitaxial layer of Mg x Ge 1-x O 2-x , with x having a value of 0≤x<1;
wherein the materials comprise at least two elements selected from Mg, Ge, and oxygen in accordance with the value of x, the Mg, Ge and oxygen being supplied by a Mg source, a Ge source, and an activated oxygen source, respectively; and
determining an elemental incident flux ratio of the Ge source to the Mg source (Φ Ge inc /Φ Mg inc ) according to a deposition surface temperature, to retain an adsorbed surface species ratio of the Ge to the Mg (Φ Ge ads /Φ Mg ads ).
18. The method of claim 17 , further comprising depositing a buffer layer between the substrate and the epitaxial layer of Mg x Ge 1-x O 2-x .
19. The method of claim 17 , wherein the co-depositing is performed using a molecular beam epitaxy process.
20. The method of claim 17 , wherein the Mg x Ge 1-x O 2-x is Mg 2 GeO 4 , wherein x=2/3.
21. The method of claim 17 , wherein the co-depositing comprises using a growth temperature of 400-500° C., and a flux ratio k of the Ge source to the Mg source (Φ Ge inc /Φ Mg inc ) of k=3 to 9.
22. The method of claim 17 , wherein the co-depositing comprises doping the epitaxial layer.
23. A method of forming a semiconductor device, the method comprising:
providing a substrate comprising a substantially single crystal substrate material that has a crystal symmetry compatible with an epitaxial layer of Mg x Ge 1-x O 2-x ;
co-depositing materials onto the substrate to form the epitaxial layer of Mg x Ge 1-x O 2-x , with x having a value of 0≤x<1;
wherein the materials comprise at least two elements selected from Mg, Ge, and oxygen in accordance with the value of x, the Mg, Ge and oxygen being supplied by a Mg source, a Ge source, and an activated oxygen source, respectively; and
forming a superlattice on the substrate, wherein the superlattice has a unit cell comprising a first layer and a second layer, wherein the first layer in the superlattice is the epitaxial layer of Mg x Ge 1-x O 2-x .
24. The method of claim 23 , wherein the second layer of the superlattice is a second epitaxial layer of Mg y Ge 1-y O 2-y , wherein y ranges from 0 to 1 and x≠y.
25. The method of claim 23 , further comprising depositing a buffer layer between the substrate and the epitaxial layer of Mg x Ge 1-x O 2-x .
26. The method of claim 23 , wherein the co-depositing is performed using a molecular beam epitaxy process.
27. The method of claim 23 , wherein the Mg x Ge 1-x O 2-x is Mg 2 GeO 4 , wherein x=2/3.
28. The method of claim 23 , wherein the co-depositing comprises using a growth temperature of 400-500° C., and a flux ratio k of the Ge source to the Mg source (Φ Ge inc /Φ Mg inc ) of k=3 to 9.
29. The method of claim 23 , wherein the co-depositing comprises doping the epitaxial layer.