Contacts for an n-type gallium and nitrogen substrate for optical devices

• US 8,802,471 B1
• Filed: 12/21/2012
• Issued: 08/12/2014
• Est. Priority Date: 12/21/2012
• Status: Active Grant

• Current Assignee: Korrus Incorporated (MKD Electric, Inc.)
• Original Assignee: Soraa, Inc.
• Inventors: Cich, Michael J., Thomson, Kenneth John
• Primary Examiner(s): Stark, Jarrett
• Assistant Examiner(s): DINKE, BITEW A
• Application Number:
  US13/723,968
• Time in Patent Office: 599 Days
• Field of Search: 438/28, 257/E33.025
• US Class Current: 438/46
• CPC Class Codes: H01L 2933/0016 relating to electrodes
• CPC Class Codes: H01L 33/0075 comprising nitride compounds
• CPC Class Codes: H01L 33/16 with a particular crystal structure or orientation, e.g. polycrystalline, amorphous or porous
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/40 Materials therefor

Abstract

Techniques for manufacturing optical devices are disclosed. More particularly, light emitting diodes and in particular to ohmic contacts for light emitting diodes are disclosed.

Claims

1. A method for fabricating LED devices, the method comprising:

providing a gallium and nitrogen containing substrate member comprising a backside surface and a front side surface, the front side surface including an n-type material overlying the substrate member, an active region overlying the n-type material, and a p-type material overlying the active region;

subjecting the backside surface to a polishing process, causing a backside surface characterized by a surface roughness;

subjecting the backside surface characterized by a surface roughness to an anisotropic etching process exposing various crystal planes to form a plurality of pyramid-like structures distributed spatially in a non-periodic manner on the backside surface, wherein the anisotropic etching process comprises use of a solution comprising silicic acid and potassium hydroxide;

treating the backside surface comprising the plurality of pyramid-like structures, to a plasma species to form a plasma-treated backside surface;

subjecting the plasma-treated backside surface to a surface treatment to form a surface-treated backside; and

forming a contact material comprising an aluminum bearing species or a titanium bearing species overlying the surface-treated backside to form a plurality of LED devices with the contact material.

2. The method of claim 1, wherein the backside surface is characterized by a nitrogen face of a c-plane, and n-type GaN characterized by a carrier concentration ranging from 1×

10¹⁵/cm³ to 1×

10²⁰/cm³;

wherein the surface roughness ranges from about 0.3 nm to 200 nm.

3. The method of claim 1, wherein the polishing process comprises use of a diamond slurry mixture characterized by a particle size ranging from 0.05 microns to 5 microns.

4. The method of claim 1, wherein each of the plurality of pyramidal-like structures is characterized by a height from about 20 nm to about 1,000 nm.

5. The method of claim 1, wherein the solution comprises 0% to 20% by weight silicic acid hydrate, and 3% to 45% by weight potassium hydroxide in water.

6. The method of claim 5, wherein the backside surface is immersed in the solution for at least 1 minute at a temperature from 0°

C. to 100°

C.

7. The method of claim 1, wherein the plasma species comprises a silicon species and a chlorine species derived from a silicon tetrachloride gas source.

8. The method of claim 1, wherein the surface treatment comprises an HCl immersion for at least one minute.

9. The method of claim 1, further comprising subjecting the LED devices to a thermal treatment process to form an ohmic contact between each LED device and the contact material.

10. A method for fabricating LED devices, the method comprising:

providing a gallium and nitrogen containing substrate member comprising a backside surface and a front side surface, the front side surface including an n-type material overlying the substrate member, an active region overlying the n-type material, and a p-type material overlying the active region;

subjecting the backside surface to a polishing process, causing a backside surface characterized by a surface roughness;

subjecting the backside surface characterized by a surface roughness to an anisotropic etching process exposing various crystal planes to form a plurality of pyramid-like structures distributed spatially in a non-periodic manner on the backside surface, the plurality of pyramid-like structures characterizing a roughened region overlying a plane within a vicinity of the backside region, wherein the anisotropic etching process comprises use of a solution comprising silicic acid and potassium hydroxide;

treating the backside surface, comprising a plurality of pyramid-like structures, to a plasma species to form a plasma-treated backside surface;

subjecting the plasma-treated backside surface to a surface treatment to form a surface-treated backside; and

forming a contact material comprising an aluminum bearing species or a titanium bearing species overlying the surface-treated backside to form a plurality of LED devices with the contact material such that the contact material forms an ohmic contact with the surface-treated backside of each of the plurality of LED devices.

11. The method of claim 10, wherein the backside surface is characterized by a nitrogen face of a c-plane, n-type GaN with carrier concentration ranging from 1×

10¹⁵/cm³ to 1×

10²⁰/cm³;

wherein the surface roughness ranges from about 0.3 nm to about 200 nm.

12. The method of claim 10, wherein the polishing process comprises use of a diamond slurry mixture characterized by a particle size from 0.05 microns to 5 microns.

13. The method of claim 10, wherein each of the plurality of pyramidal like structures is characterized by a height from 20 nm to 1000 nm.

14. The method of claim 10, wherein the solution comprises 0% to 20% by weight silicic acid hydrate, and 3% to 45% by weight potassium hydroxide in water.

15. The method of claim 14, wherein the backside surface is immersed in the solution for at least 1 minute at a temperature from 0°

C. to 100°

C.

16. The method of claim 10, wherein the plasma species comprises a silicon species and a chlorine species derived from a silicon tetrachloride gas source.

17. The method of claim 10, wherein the surface treatment comprises an HCl immersion for at least one minute.

18. The method of claim 10 further comprising subjecting the LED devices to a thermal treatment process to form the ohmic contact between each LED device and the contact material.