Composite high reflectivity layer

• US 8,598,609 B2
• Filed: 03/24/2011
• Issued: 12/03/2013
• Est. Priority Date: 12/08/2008
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Ibbetson, James, Li, Ting, Hansen, Monica
• Primary Examiner(s): YUSHIN, NIKOLAY K
• Application Number:
  US13/071,349
• Publication Number:
  US 20110169036A1
• Time in Patent Office: 985 Days
• Field of Search: 257/13, 257/79, 257/98, 257/E33.068
• US Class Current: 257/98
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 33/10 with a light reflecting structure, e.g. semiconductor Bragg reflector
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector

Abstract

A high efficiency light emitting diode with a composite high reflectivity layer integral to said LED to improve emission efficiency. One embodiment of a light emitting diode (LED) chip comprises an LED and a composite high reflectivity layer integral to the LED to reflect light emitted from the active region. The composite layer comprises a first layer, and alternating plurality of second and third layers on the first layer, and a reflective layer on the topmost of said plurality of second and third layers. The second and third layers have a different index of refraction, and the first layer is at least three times thicker than the thickest of the second and third layers. For composite layers internal to the LED chip, conductive vias can be included through the composite layer to allow an electrical signal to pass through the composite layer to the LED.

Claims

1. A light emitting diode (LED) chip, comprising:

an active region between two oppositely doped layers;

a composite high reflectivity layer arranged to reflect light emitted from said active region, said composite layer comprising;

a first layer;

one or more second layers and a plurality of third layers on said first layer, said second layers having an index of refraction different from said third layers, wherein at least one of said second layers is interposed between two of said third layers, and each of said third layers having different thicknesses compared to the other of said third layers; and

a reflective layer on the topmost of said second and third layers,

wherein said composite layer further comprises an interconnect grid.

2. A light emitting diode (LED) chip, comprising:

an active region between two oppositely doped layers;

a composite high reflectivity layer arranged to reflect light emitted from said active region, said composite layer comprising;

a first layer;

one or more second layers and a plurality of third layers on said first layer, said second layers having an index of refraction different from said third layers, wherein at least one of said second layers is interposed between two of said third layers, and each of said third layers having different thicknesses compared to the other of said third layers, wherein said first layer is thicker than the thickest of said second and third layers; and

a reflective layer on the topmost of said second and third layers.

3. The LED chip of claim 2, wherein said first layer comprises a dielectric material.

4. The LED chip of claim 2, wherein said first layer is at least three times thicker than the thickest of said second and third layers.

5. The LED chip of claim 2, wherein said first layer has a thickness in the range of 500 to 650 nanometers.

6. The LED chip of claim 2, further comprising a current spreading layer.

7. The LED chip of claim 6, wherein said current spreading layer comprises indium tin oxide (ITO).

8. The LED chip of claim 2, wherein said one or more second layers comprise silicon dioxide (SiO₂).

9. The LED chip of claim 2, wherein said one or more second layers comprise two second layers.

10. The LED chip of claim 9, wherein the first of said two second layers has a thickness in the range of 100 to 120 nanometers and the second of said two second layers has a thickness in the range of 40 to 60 nanometers.

11. The LED chip of claim 2, wherein said plurality of third layers comprise titanium dioxide (TIO₂).

12. The LED chip of claim 2, wherein said plurality of third layers comprise two third layers.

13. The LED chip of claim 12, wherein the first of said two third layers has a thickness in the range of 55 to 75 nanometers and the second of said two third layers has a thickness in the range of 35 to 55 nanometers.

14. The LED chip of claim 2, wherein said composite layer further comprises holes.

15. The LED chip of claim 14, wherein said holes are filled with a conductive material.

16. A light emitting diode (LED) chip, comprising:

an active region between two oppositely doped layers;

a composite high reflectivity layer arranged to reflect light emitted from said active region, said composite layer comprising;

a first layer;

one or more second layers and a plurality of third layers on said first layer, said second layers having an index of refraction different from said third layers, wherein at least one of said second layers is interposed between two of said third layers, and each of said third layers having different thicknesses compared to the other of said third layers, wherein said first layer is thicker than the thickest of said second and third layers; and

a reflective layer on the topmost of said second and third layers,

wherein said composite layer further comprises an interconnect grid.

17. A light emitting diode (LED) chip, comprising:

an active region between two oppositely doped layers;

a composite high reflectivity layer arranged to reflect light emitted from said active region, said composite layer comprising;

a first layer;

one or more second layers and a plurality of third layers on said first layer, said second layers having an index of refraction different from said third layers, wherein at least one of said second layers is interposed between two of said third layers, and each of said third layers having different thicknesses compared to the other of said third layers;

a reflective layer on the topmost of said second and third layers; and

a current spreading layer between said active region and said composite layer.

18. The LED chip of claim 17, wherein said first layer comprises a dielectric material.

19. The LED chip of claim 17, wherein said first layer is thicker than the thickest of said second and third layers.

20. The LED chip of claim 19, wherein said first layer is at least three times thicker than the thickest of said second and third layers.

21. The LED chip of claim 17, wherein said first layer has a thickness in the range of 500 to 650 nanometers.

22. The LED chip of claim 17, wherein said current spreading layer comprises indium tin oxide (ITO).

23. The LED chip of claim 17, wherein said one or more second layers comprise silicon dioxide (SiO₂).

24. The LED chip of claim 17, wherein said one or more second layers comprise two second layers.

25. The LED chip of claim 24, wherein the first of said two second layers has a thickness in the range of 100 to 120 nanometers and the second of said two second layers has a thickness in the range of 40 to 60 nanometers.

26. The LED chip of claim 17, wherein said plurality of third layers comprise titanium dioxide (TIO₂).

27. The LED chip of claim 17, wherein said plurality of third layers comprise two third layers.

28. The LED chip of claim 27, wherein the first of said two third layers has a thickness in the range of 55 to 75 nanometers and the second of said two third layers has a thickness in the range of 35 to 55 nanometers.

29. The LED chip of claim 17, wherein said composite layer further comprises holes.

30. The LED chip of claim 29, wherein said holes are filled with a conductive material.

31. A light emitting diode (LED) chip, comprising:

an active region between two oppositely doped layers;

a composite high reflectivity layer arranged to reflect light emitted from said active region, said composite layer comprising;

a first layer;

one or more second layers and a plurality of third layers on said first layer, said second layers having an index of refraction different from said third layers, wherein at least one of said second layers is interposed between two of said third layers, and each of said third layers having different thicknesses compared to the other of said third layers;

a reflective layer on the topmost of said second and third layers; and

a current spreading layer between said active region and said composite layer,

wherein said composite layer further comprises an interconnect grid.

32. A light emitting diode (LED) chip, comprising:

an active region between two oppositely doped layers;

a composite high reflectivity layer arranged to reflect light emitted from said active region, said composite layer comprising;

a first layer;

one or more second layers and a plurality of third layers on said first layer, said second layers having an index of refraction different from said third layers, wherein at least one of said second layers is interposed between two of said third layers, each of said third layers having different thicknesses compared to the other of said third layers, and wherein the number of said third layers is greater than the number of said second layers; and

a reflective layer on the topmost of said second and third layers.