Optically initiated silicon carbide high voltage switch
View Patent ↗An improved photoconductive switch having a SiC or other wide band gap substrate material, such as GaAs and field-grading liners composed of preferably SiN formed on the substrate adjacent the electrode perimeters or adjacent the substrate perimeters for grading the electric fields.
1. A photoconductive switch comprising,
a photoconductive substrate composed of a greater-than-1.6 eV wide band gap material, said substrate having at least one concavity(s), and a facet optically connectable to an optical source for receiving optical energy therefrom;
two electrodes electrically connected to the substrate with at least one of the electrodes having a convex surface contactedly seated in a corresponding one of the at least one concavity(s), for applying a potential across the substrate; and
two field-grading liners formed on the substrate surrounding the electrode-contacting surfaces, for grading the electric fields therealong.
2. The photoconductive switch of claim 1 ,
wherein the two field-grading liners are adjacent the electrode perimeters.
3. The photoconductive switch of claim 2 ,
wherein the two field-grading liners form the rims of the two concavities for grading the electric fields at the separations of the electrodes from the substrate.
4. The photoconductive switch of claim 1 ,
wherein the field-grading liners are integrally formed on the substrate.
5. The photoconductive switch of claim 1 ,
wherein the field-grading liners are a high permittivity material.
6. The photoconductive switch of claim 1 ,
wherein the field-grading liners are selected from a group consisting of conductive and semi-conductive materials.
7. The photoconductive switch of claim 6 ,
wherein the field-grading liners are composed of silicon nitride.
8. The photoconductive switch of claim 6 ,
wherein the conductive or semi-conductive material is formed as a doped sub-surface layer of the substrate.
9. The photoconductive switch of claim 8 ,
wherein the doped sub-surface conductive or semi-conductive sub-surface layer extends into the substrate about 1 micron deep.
10. The photoconductive switch of claim 1 ,
wherein the substrate is a multilayer having at least two photoconductive layers separated by a divider layer.
11. The photoconductive switch of claim 10 ,
wherein the divider layer is selected from a group consisting of conductive and semi-conductive materials.
12. The photoconductive switch of claim 1 ,
wherein the substrate is a compensated, semi-insulating material selected from a group consisting of 4h SiC, 6h SiC, and GaN.
13. The photoconductive switch of claim 12 ,
wherein the substrate is semi-insulating SiC having a hexagonal crystal structure and cut in a plane selected from the group consisting of the A-Plane, C-Plane and M-plane.
14. The photoconductive switch of claim 13 ,
wherein the substrate comprises at least two layers cut in the C-Plane and offset from each other.
15. The photoconductive switch of claim 12 ,
wherein the semi-insulating SiC is doped with at least one of the following dopants: Boron, Vanadium, Nitrogen, Aluminum, Phosphorus, Oxygen, Tungsten and Zinc.
16. The photoconductive switch of claim 1 ,
wherein at least one facet of the substrate is coated with a dielectric to produce total internal reflection.
17. A photoconductive switch comprising:
a photoconductive substrate composed of a greater-than- 1 . 6 eV wide band gap material, said substrate having opposing electrode-contacting surfaces and a facet optically connectable to an optical source for receiving optical energy therefrom;
two electrodes electrically connected to the electrode-contacting surfaces of the substrate, for applying a potential across the substrate; and
at least one field-grading liner(s) formed on the substrate surrounding a corresponding one of the electrode-contacting surfaces, for grading the electric fields therealong.
18. The photoconductive switch of claim 17 ,
wherein the field-grading liners are adjacent the electrode perimeters.
19. The photoconductive switch of claim 18 ,
wherein the field-grading liners are formed between the substrate and the electrode perimeters.
20. The photoconductive switch of claim 19 ,
wherein the two field-grading liners are recessed below the level of the electrode-contacting surfaces.
21. The photoconductive switch of claim 20 ,
wherein outer surfaces of the field-grading liners are coplanar with the electrode-contacting surfaces to foiln extensions thereof.
22. The photoconductive switch of claim 17 ,
wherein the field-grading liners are adjacent the substrate perimeter.
23. The photoconductive switch of claim 17 ,
wherein the field-grading liners are integrally formed on the substrate.
24. The photoconductive switch of claim 17 ,
wherein the field-grading liners are a high permittivity material.
25. The photoconductive switch of claim 17 ,
wherein the field-grading liners are selected from a group consisting of conductive and semi-conductive materials.
26. The photoconductive switch of claim 25 ,
wherein the field-grading liners are composed of silicon nitride.
27. The photoconductive switch of claim 25 ,
wherein the conductive or semi-conductive material is formed as a doped sub-surface layer of the substrate.
28. The photoconductive switch of claim 27 ,
wherein the doped sub-surface conductive or semi-conductive sub-surface layer extends into the substrate about 1 micron deep.
29. The photoconductive switch of claim 17 ,
wherein the substrate is a multilayer having at least two photoconductive layers separated by a divider layer.
30. The photoconductive switch of claim 29 ,
wherein the divider layer is selected from a group consisting of conductive and semi-conductive materials.
31. The photoconductive switch of claim 17 ,
wherein the substrate is a compensated, semi-insulating material selected from a group consisting of 4h SiC, 6h SiC, and GaN.
32. The photoconductive switch of claim 31 ,
wherein the substrate is semi-insulating SiC having a hexagonal crystal structure and cut in a plane selected from the group consisting of the A-Plane, C-Plane and M-plane.
33. The photoconductive switch of claim 32 ,
wherein the substrate comprises at least two layers cut in the C-Plane and offset from each other.
34. The photoconductive switch of claim 31 ,
wherein the semi-insulating SiC is doped with at least one of the following dopants: Boron, Vanadium, Nitrogen, Aluminum, Phosphorus, Oxygen, Tungsten and Zinc.
35. The photoconductive switch of claim 17 ,
wherein at least one facet of the substrate is coated with a dielectric to produce total internal reflection.