Light emitting diodes including current spreading layer and barrier sublayers

• US 8,907,366 B2
• Filed: 10/30/2013
• Issued: 12/09/2014
• Est. Priority Date: 07/23/2001
• Status: Expired due to Fees

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Slater, David B. Jr., Williams, Bradley E., Andrews, Peter S., Edmond, John A., Allen, Scott T.
• Primary Examiner(s): TRAN, MINH LOAN
• Application Number:
  US14/067,395
• Publication Number:
  US 20140048822A1
• Time in Patent Office: 405 Days
• Field of Search: 257/98, 257/99, 257/751, 257/E33.068, 257/E33.069
• US Class Current: 257/98
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/01057 Lanthanum [La]
• CPC Class Codes: H01L 2924/12041 LED
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/405 Reflective materials
• CPC Class Codes: H01L 33/44 characterised by the coatings, e.g. passivation layer or anti-reflective coating
• CPC Class Codes: H01L 33/60 Reflective elements
• CPC Class Codes: H01L 33/62 Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls

Abstract

Semiconductor light emitting devices, such as light emitting diodes, include a substrate, an epitaxial region on the substrate that includes a light emitting region such as a light emitting diode region, and a multilayer conductive stack including a current spreading layer, on the epitaxial region. A barrier layer is provided on the current spreading layer and extending on a sidewall of the current spreading layer. The multilayer conductive stack can also include an ohmic layer between the reflector and the epitaxial region. The barrier layer further extends on a sidewall of the ohmic layer. The barrier layer can also extend onto the epitaxial region outside the multilayer conductive stack. The barrier layer can be fabricated as a series of alternating first and second sublayers.

Claims

1. A semiconductor light emitting device comprising:

a semiconductor region that comprises a light-emitting region;

a current spreading layer on the semiconductor region; and

a conductive barrier layer on the current spreading layer, the conductive barrier layer comprising a plurality of first spaced-apart sublayers.

2. A light emitting device according to claim 1 wherein the conductive barrier layer that comprises the plurality of first spaced-apart sublayers further extends onto the semiconductor region outside the current spreading layer.

3. A light emitting device according to claim 1 wherein the conductive barrier layer comprises a plurality of the first and second alternating sublayers.

4. A light emitting device according to claim 3 wherein the first sublayers include grain boundaries therein and wherein the second sublayers are substantially free of grain boundaries.

5. A light emitting device according to claim 3 wherein the first sublayers comprise titanium tungsten and wherein the second sublayers comprise platinum, titanium and/or nickel.

6. A light emitting device according to claim 3 wherein the first sublayers are configured to reduce migration of metal from the current spreading layer and wherein the second sublayers are configured to prevent at least some grain boundaries in the first sublayers from propagating thereacross.

7. A light emitting device according to claim 3 wherein the first sublayers are sufficiently thick to reduce migration of metal from the current spreading layer but sufficiently thin to prevent at least some cracking of the first sublayers and wherein the second sublayers are sufficiently thick to prevent at least some grain boundaries in the first sublayers from propagating thereacross but sufficiently thin so as not to degrade contact resistance of the light emitting device.

8. A light emitting device according to claim 3 wherein the first sublayers comprise titanium tungsten and wherein the second sublayers comprise platinum, titanium and/or nickel.

9. A light emitting device according to claim 1 further comprising:

a bond on the conductive barrier layer; and

a submount on the bond, opposite the conductive barrier layer.

10. A light emitting device according to claim 9 wherein the semiconductor region comprises n-type and p-type layers, and wherein the current spreading layer is adjacent the p-type layer and between the p-type layer and the submount.

11. A light emitting device according to claim 10 wherein the n-type and p-type layers each comprise a Group III nitride.

12. A light emitting device according to claim 9 wherein the bond comprises a thermocompression bond.

13. A light emitting device according to claim 9 wherein the bond comprises solder.

14. A light emitting device according to claim 13 wherein the solder comprises tin and/or gold.

15. A light emitting diode according to claim 1 wherein the current spreading layer comprises aluminum and/or silver.

16. A light emitting device according to claim 1 further comprising:

a transparent ohmic contact between the semiconductor region and the current spreading layer.

17. A light emitting device according to claim 16 wherein the transparent ohmic contact comprises metal.

18. A light emitting device according to claim 17 wherein the transparent ohmic contact that comprises metal is between about 10 Å

and about 100 Å

in thickness.

19. A light emitting device according to claim 16 wherein the current spreading layer comprises aluminum and/or silver and the transparent ohmic contact comprises platinum, palladium, nickel, titanium and/or gold.

20. A light emitting device according to claim 16 wherein the current spreading layer comprises silver and the transparent ohmic contact comprises nickel and/or platinum.

21. A light emitting device according to claim 16 wherein the current spreading layer is configured to spread electric current uniformly across the transparent ohmic contact.

22. A light emitting device according to claim 1 wherein the first sublayers include grain boundaries therein that are arranged such that the grain boundaries define an offset brick wall structure in the first sublayers.

23. A light emitting device according to claim 1 further comprising an ohmic layer between the current spreading layer and the conductive barrier layer.

24. A light emitting device according to claim 1 wherein the semiconductor region comprises n-type and p-type layers and an active region therebetween, and wherein the current spreading layer is adjacent the p-type layer.

25. A light emitting device according to claim 24 wherein the n-type and p-type layers and the active region each comprises a Group III nitride.

26. A light emitting device according to claim 1 wherein the semiconductor region comprises gallium nitride.

27. A light emitting device according to claim 1 wherein the semiconductor region comprises an epitaxial region on a substrate.

28. A light emitting device according to claim 27 wherein the substrate comprises silicon carbide and the epitaxial region comprises gallium nitride.