Optically initiated silicon carbide high voltage switch

• US 20070092812A1
• Filed: 10/24/2006
• Published: 04/26/2007
• Est. Priority Date: 10/24/2005
• Status: Active Grant

• Current Assignee: Lawrence Livermore National Security LLC (Government of the United States of America)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Sampayan, Stephen, Sanders, David, Caporaso, George, Sullivan, James
• Granted Patent: US 7,893,541 B2
• Time in Patent Office: Days
• US Class Current: 430/57.7
• CPC Class Codes: H01L 31/09 Devices sensitive to infrared, visible or ultraviolet radiation H01L31/101 takes precedence
• CPC Class Codes: H05H 7/00 Details of devices of the types covered by groups H05H9/00, H05H11/00, H05H13/00

Abstract

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.

Claims

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; and

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.

2. The photoconductive switch of claim 1,

further comprising two field-grading liners formed on the substrate surrounding the electrode-contacting surfaces, for grading the electric fields therealong.

3. The photoconductive switch of claim 2,

wherein the two field-grading liners are adjacent the electrode perimeters.

4. The photoconductive switch of claim 3,

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.

5. The photoconductive switch of claim 2,

wherein the field-grading liners are integrally formed on the substrate.

6. The photoconductive switch of claim 2,

wherein the field-grading liners are a high permittivity material.

7. The photoconductive switch of claim 2,

wherein the field-grading liners are selected from a group consisting of conductive and semi-conductive materials.

8. The photoconductive switch of claim 7,

wherein the field-grading liners are composed of silicon nitride.

9. The photoconductive switch of claim 7,

wherein the conductive or semi-conductive material is formed as a doped sub-surface layer of the substrate.

10. The photoconductive switch of claim 9,

wherein the doped sub-surface conductive or semi-conductive sub-surface layer extends into the substrate about 1 micron deep.

11. The photoconductive switch of claim 1,

wherein the substrate is a multilayer having at least two photoconductive layers separated by a divider layer.

12. The photoconductive switch of claim 11,

wherein the divider layer is selected from a group consisting of conductive and semi-conductive materials

13. 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.

14. The photoconductive switch of claim 13,

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.

15. The photoconductive switch of claim 14,

wherein the substrate comprises at least two layers cut in the C-Plane and offset from each other.

16. The photoconductive switch of claim 13,

wherein the semi-insulating SiC is doped with at least one of the following dopants:

Boron, Vanadium, Nitrogen, Aluminum, Phosphorus, Oxygen, Tungsten and Zinc.

17. The photoconductive switch of claim 1,

wherein at least one facet of the substrate is coated with a dielectric to produce total internal reflection.

18. 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.

19. The photoconductive switch of claim 18,

wherein the field-grading liners are adjacent the electrode perimeters.

20. The photoconductive switch of claim 19,

wherein the field-grading liners are formed between the substrate and the electrode perimeters.

21. The photoconductive switch of claim 20,

wherein the two field-grading liners are recessed below the level of the electrode-contacting surfaces.

22. The photoconductive switch of claim 21,

wherein outer surfaces of the field-grading liners are coplanar with the electrode-contacting surfaces to form extensions thereof.

23. The photoconductive switch of claim 18,

wherein the field-grading liners are adjacent the substrate perimeter.

24. The photoconductive switch of claim 18,

wherein the field-grading liners are integrally formed on the substrate.

25. The photoconductive switch of claim 18,

wherein the field-grading liners are a high permittivity material.

26. The photoconductive switch of claim 18,

wherein the field-grading liners are selected from a group consisting of conductive and semi-conductive materials.

27. The photoconductive switch of claim 26,

wherein the field-grading liners are composed of silicon nitride.

28. The photoconductive switch of claim 26,

wherein the conductive or semi-conductive material is formed as a doped sub-surface layer of the substrate.

29. The photoconductive switch of claim 28,

wherein the doped sub-surface conductive or semi-conductive sub-surface layer extends into the substrate about 1 micron deep.

30. The photoconductive switch of claim 18,

wherein the substrate is a multilayer having at least two photoconductive layers separated by a divider layer.

31. The photoconductive switch of claim 30,

wherein the divider layer is selected from a group consisting of conductive and semi-conductive materials

32. The photoconductive switch of claim 18,

wherein the substrate is a compensated, semi-insulating material selected from a group consisting of 4h SiC, 6h SiC, and GaN.

33. The photoconductive switch of claim 32,

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.

34. The photoconductive switch of claim 33,

wherein the substrate comprises at least two layers cut in the C-Plane and offset from each other.

35. The photoconductive switch of claim 32,

wherein the semi-insulating SiC is doped with at least one of the following dopants:

Boron, Vanadium, Nitrogen, Aluminum, Phosphorus, Oxygen, Tungsten and Zinc.

36. The photoconductive switch of claim 18,

wherein at least one facet of the substrate is coated with a dielectric to produce total internal reflection.