Reliable electrical contacts for high power photoconductive switches

Patent metadata

Field	Value
Publication number	US-10134927-B2
Application number	US-201615206133-A
Country	US
Kind code	B2
Filing date	Jul 8, 2016
Priority date	Jul 8, 2016
Publication date	Nov 20, 2018
Grant date	Nov 20, 2018

Abstract

A photoconductive switch consisting of an optically actuated photoconductive material, e.g. a wide bandgap semiconductor such as SiC, situated between opposing electrodes. The electrodes are created using various methods in order to maximize reliability by reducing resistive heating, current concentrations and filamentation, and heating and ablation due to the light source. This is primarily accomplished by the configuration of the electrical contact geometry, choice of contacts metals, annealing, ion implantation, creation of recesses within the SiC, and the use of coatings to act as encapsulants and anti-reflective layers.

First claim

What is claimed is:

1. A photoconductive switch, comprising:
a first metal contact;
a photoconductive material;
a second metal contact, wherein the photoconductive material is placed between the first and the second metal contacts, the second metal contact comprising an opening to allow light to be coupled to the photoconductive material for activation of the photoconductive material; and
a highly conductive and transparent layer between the second metal contact and the photoconductive material.

2. The photoconductive switch of claim 1 , wherein the second metal contact comprises a metal that is annealed at a high temperature to form an Ohmic contact on the photoconductive material.

3. The photoconductive switch of claim 2 , wherein the Ohmic contact forms a conductive region in the photoconductive material to reduce current constriction.

4. The photoconductive switch of claim 1 , wherein the first metal contact comprises a highly reflective metal layer positioned between at least a portion of the first metal contact and the photoconductive material to allow the light that passes through the photoconductive material to reflect back and pass through the photoconductive material for a second time.

5. The photoconductive switch of claim 1 , further comprising a metal grid positioned within at least a section of the opening of the second metal contact, the metal grid including a plurality of regions that allow propagation of light therethrough.

6. The photoconductive switch of claim 5 , further comprising a highly reflective metal layer positioned on a surface of the second metal contact or the metal grid that faces away from the photoconductive material to reduce absorption of the light by the second metal contact or the metal grid.

7. The photoconductive switch of claim 6 , wherein the highly reflective metal layer and area beneath the second metal contact include improved Ohmicity due to exposure to plasma or chemical treatment.

8. The photoconductive switch of claim 5 , wherein the metal grid includes curved bends.

9. The photoconductive switch of claim 5 , wherein the metal grid includes multiple sections having non-uniform widths.

10. The photoconductive switch of claim 5 , wherein the second metal contact and the metal grid are partially positioned within the photoconductive material.

11. The photoconductive switch of claim 5 , further comprising a high energy ion implantation region positioned within the photoconductive material in contact with the metal grid and the second metal contact.

12. The photoconductive switch of claim 5 , wherein the metal grid and the second metal contact comprise different materials.

13. The photoconductive switch of claim 5 , further comprising an antireflection dielectric coating layer that covers (a) at least a surface of the second metal contact that faces away from the photoconductive material and (b) at least a section of the photoconductive material.

14. The photoconductive switch of claim 13 , wherein the antireflection dielectric coating layer further covers at least a surface of the metal grid.

15. The photoconductive switch of claim 5 , further comprising a doped region within the photoconductive material in the vicinity of the metal grid or at least a section of the second metal contact.

16. The photoconductive switch of claim 1 , wherein the first metal contact comprises an opening to allow the light that propagates through the photoconductive material to exit.

17. The photoconductive switch of claim 16 , wherein further including an additional photoconductive switch that is positioned in a stacked position with respect to the photoconductive switch such that the light that propagates through the photoconductive material and exits the opening of the first metal contact is coupled to the additional photoconductive switch.

18. The photoconductive switch of claim 16 , further comprising an additional metal grid positioned within the opening of the first metal contact.

19. The photoconductive switch of claim 18 , further comprising a highly reflective metal layer positioned on one side of the first metal contact or the additional metal grid.

20. The photoconductive switch of claim 18 , wherein the additional metal grid includes sections with curved bends.

21. The photoconductive switch of claim 18 , wherein the additional metal grid includes a plurality of sections having non-uniform widths.

22. The photoconductive switch of claim 18 , wherein the metal grid and the additional metal grid are positioned within the openings of the second metal contact and the first metal contact, respectively, such that boundaries of one or more sections of the metal grid and the additional metal grid are aligned.

23. The photoconductive switch of claim 18 , wherein the first metal contact and the additional metal grid are partially positioned within the photoconductive material.

24. The photoconductive switch of claim 18 , further comprising a high energy ion implantation region positioned within the photoconductive material in contact with the additional metal grid and the first metal contact.

25. The photoconductive switch of claim 18 , wherein the additional metal grid comprises a different metal than the first metal contact.

26. The photoconductive switch of claim 18 , further comprising a doped region within the photoconductive material proximate to the additional metal grid.

27. A high power photoconductive axial switch, comprising:
a light source to produce light;
an electrical power supply to apply a high voltage;
a top electrode coupled to the electrical power supply, comprising an opening to allow the light from the light source to enter the opening;
a photoconductive material placed below the top electrode;
a bottom electrode placed below the photoconductive material; and
a highly conductive and transparent layer between the top electrode and the photoconductive material,
wherein the photoconductive material exhibits an electrical conductivity change in response to the light to turn on or off the electrical path between the top electrode and the bottom electrode.

28. The high power photoconductive axial switch of claim 27 , further comprising a metal grid positioned within at least a section of the opening of the top electrode, the metal grid including a plurality of regions that allow propagation of light therethrough.

Assignees

• L Livermore Nat Security Llc

Inventors

• Voss Lars
• Bora Mihail
• Caporaso George
• Conway Adam
• Nguyen Hoang T
• Nikolic Rebecca J
• Sampayan Stephen E
• Park Sangtae

Classifications

• H01L31/09

  Electricity · mapped topic

• G02B6/4295

  coupling with semiconductor devices activated by light through the light guide, e.g. thyristors, phototransistors · CPC title

• H01L31/02327 Primary

  Electricity · mapped topic

• H01L31/0312

  Electricity · mapped topic

• H10F77/1226

  comprising multiple Group IV elements, e.g. SiC · CPC title