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

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 1×10 15 /cm 3 to 1×10 20 /cm 3 ; 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 1×10 15 /cm 3 to 1×10 20 /cm 3 ; 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.