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

• US 9,379,280 B2
• Filed: 08/17/2015
• Issued: 06/28/2016
• Est. Priority Date: 07/09/2013
• Status: Active Grant

• Current Assignee: Korrus Incorporated (MKD Electric, Inc.)
• Original Assignee: Soraa, Inc.
• Inventors: Cich, Michael J., Thomson, Kenneth John
• Primary Examiner(s): Valentine, Jami M
• Application Number:
  US14/827,709
• Publication Number:
  US 20150357513A1
• Time in Patent Office: 316 Days
• Field of Search: 257/13, 257/76, 257/33.012, 438/46, 438/34
• US Class Current: 1/1
• CPC Class Codes: H01L 2933/0008 Processes
• CPC Class Codes: H01L 2933/0016 relating to electrodes
• CPC Class Codes: H01L 2933/0033 relating to semiconductor body packages
• CPC Class Codes: H01L 33/0075 comprising nitride compounds
• 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 33/38 with a particular shape
• CPC Class Codes: H01L 33/382 the electrode extending partially in or entirely through the semiconductor body
• CPC Class Codes: H01L 33/40 Materials therefor
• CPC Class Codes: H01L 33/405 Reflective materials

Abstract

A method for fabricating LED devices. The method includes providing a gallium and nitrogen containing substrate member (e.g., GaN) comprising a backside surface and a front side surface. The method includes subjecting the backside surface to a polishing process, causing a backside surface to be characterized by a surface roughness, subjecting the backside surface 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, treating the backside surface comprising the plurality of pyramid-like structures, to a plasma species, and subjecting the backside surface to a surface treatment. The method further includes 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.

Claims

1. A method for roughening a semiconductor structure comprising at least a III-Nitride material and having at least one nitrogen-face side having an initial roughness, said method comprising:

contacting said side with at least one mixture containing an acid and an alkali hydroxide, thereby roughening said side to a second roughness, said second roughness being rougher than said initial roughness.

2. The method of claim 1, wherein said alkali hydroxide comprises potassium hydroxide.

3. The method of claim 2, wherein said acid is at least one of silicic acid, boric acid, chlorosulfonic acid, sulfamic acid.

4. The method of claim 3, wherein said at least one mixture comprises at least potassium hydroxide and silicic acid.

5. The method of claim 1, wherein said initial roughness has an RMS roughness lower than 100 nm.

6. The method of claim 1, wherein said second roughness comprises at least a plurality of pyramid-like structures, having an apex and a base.

7. The method of claim 6, wherein at least a portion of said pyramid-like structures have six sides extends from said apex to said base.

8. The method of claim 6, wherein at least a portion of said pyramids have a nominal base dimension of about 5 um.

9. The method of claim 6, wherein the bases of said pyramid-like structures are substantially contiguous to define a plane.

10. The method of claim 6, wherein at least 80% of said pyramid-like structures have a base having a normalized size ranging from 0.3 to 3 relative to the median base size of said pyramid-like structures.

11. The method of claim 1 further comprising subsequently contacting said side with a second mixture containing at least one of an acid or an alkali hydroxide.

12. The method of claim 1, wherein said at least one mixture comprises at least 0% to 20% by weight of silicic acid hydrate and 3% to 45% by weight of alkali hydroxide in water.

13. The method of claim 1, wherein said at least one mixture contacts said side for at least 1 minute.

14. The method of claim 1, wherein said at least one mixture contacts said side at between 0°

C. and 100°

C.

15. The method of claim 1, wherein said contacting comprises continuously agitating said at least one mixture to provide uniformity of roughness.

16. The method of claim 1, wherein said semiconductor structures comprises light-emitting layers.

17. The method of claim 1, wherein said side is n-doped.

18. A semiconductor structure made from the method of claim 1.

19. A semiconductor structure made from the method of claim 12.