Light emitting diodes including barrier layers/sublayers

• US 7,211,833 B2
• Filed: 01/20/2005
• Issued: 05/01/2007
• Est. Priority Date: 07/23/2001
• Status: Expired due to Term

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Andrews, Peter S., Williams, Bradley E., Slater, David B. Jr., Edmond, John A., Allen, Scott T.
• Primary Examiner(s): TRAN, MINH LOAN
• Application Number:
  US11/039,566
• Publication Number:
  US 20050194603A1
• Time in Patent Office: 831 Days
• Field of Search: 257/98, 257/99, 257/751, 257/767, 257/744, 257/745, 257/E33.062, 257/E33.068
• 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 reflector layer, on the epitaxial region. A barrier layer is provided on the reflector layer and extending on a sidewall of the reflector 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 includes therein a light-emitting region;

a multilayer conductive stack comprising a reflector layer including a reflector layer sidewall, on the semiconductor region, and an ohmic contact layer including an ohmic contact layer sidewall, between the reflector layer and the semiconductor region; and

a conductive barrier layer directly on the reflector layer and extending directly on the reflector layer sidewall and directly on the ohmic contact layer sidewall.

2. A light emitting device according to claim 1 wherein the conductive barrier layer further extends onto the semiconductor region outside the multilayer conductive stack.

3. A light emitting device according to claim 1 wherein the conductive barrier layer comprises a plurality of 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 include grain boundaries therein that are arranged such that the grain boundaries define an offset brick wall structure in the first sublayers.

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

7. A light emitting device according to claim 6 wherein the second sublayers are thinner than the first sublayers.

8. A light emitting device according to claim 7 wherein the plurality of first and second alternating sublayers include a first sublayer that is closest to the reflector layer and a first sublayer that is furthest from the reflector layer.

9. A light emitting device according to claim 8 wherein the first sublayer that is furthest from the reflector layer is thicker than the first sublayer that is closest to the reflector layer.

10. A light emitting device according to claim 9 wherein the first sublayers comprise titanium tungsten sublayers that are about 1000 Å

thick, wherein the second sublayers comprise platinum sublayers that are about 500 Å

thick, wherein the first sublayer that is closest to the reflector layer comprises a titanium tungsten sublayer that is about 1000 Å

thick and wherein the first sublayer that is farthest from the reflector layer comprises a titanium tungsten sublayer that is about 5000 Å

thick.

11. A light emitting device according to claim 5 wherein the first sublayers are configured to reduce migration of metal from the reflector layer and wherein the second sublayers are configured to prevent at least some grain boundaries in the first sublayers from propagating thereacross.

12. 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.

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

14. A light emitting device according to claim 3 wherein the second sublayers are thinner than the first sublayers.

15. A light emitting device according to claim 3 wherein the plurality of first and second alternating sublayers include a first sublayer that is closest to the reflector layer and a first sublayer that is furthest from the reflector layer.

16. A light emitting device according to claim 15 wherein the first sublayer that is furthest from the reflector layer is thicker than the first sublayer that is closest to the reflector layer.

17. A light emitting device according to claim 3 wherein the first sublayers comprise titanium tungsten sublayers that are about 1000 Å

thick and wherein the second sublayers comprise platinum sublayers that are about 500 Å

thick.

18. A light emitting device according to claim 3 wherein the first sublayers are sufficiently thick to reduce migration of metal from the reflector 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 resistance of the multilayer conductive stack.

19. A light emitting device according to claim 1 wherein the conductive barrier layer is configured to prevent at least some cracks from occurring therein, adjacent the reflector layer sidewall.

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

21. A light emitting diode according to claim 1 wherein the ohmic contact layer comprises platinum, palladium, nickel/gold, nickel oxide/gold, nickel oxide/platinum, titanium and/or titanium/gold and wherein the reflector layer comprises aluminum and/or silver.

22. A light emitting device according to claim 1 wherein the reflector layer comprises silver.

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

24. A light emitting device according to claim 23 wherein the substrate comprises silicon carbide and the epitaxial region comprises gallium nitride.