Method of forming light emitting devices with improved light extraction efficiency

• US 7,279,345 B2
• Filed: 09/10/2004
• Issued: 10/09/2007
• Est. Priority Date: 09/12/2000
• Status: Expired due to Term

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Philips Lumileds Lighting Company LLC (Apollo Global Management, Inc.)
• Inventors: Krames, Michael R., Mueller-Mach, Regina B., Mueller, Gerd O., Steranka, Frank M., Camras, Michael D., Taber, Robert C., Trottier, Troy A., Hofler, Gloria E., Uebbing, John J., Lowery, Christopher H., Snyder, Wayne L., Pocius, Douglas W.
• Primary Examiner(s): Picardat; Kevin M.
• Application Number:
  US10/938,237
• Publication Number:
  US 20050032257A1
• Time in Patent Office: 1,124 Days
• Field of Search: 438/22, 438/26, 438/27, 438/29, 438/69, 438/71, 438/72, 438/65, 257/E33.067
• US Class Current: 438/27
• 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 33/502 Wavelength conversion materials
• CPC Class Codes: H01L 33/58 Optical field-shaping 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

A method of bonding a transparent optical element to a light emitting device having a stack of layers including semiconductor layers comprising an active region is provided. The method includes elevating a temperature of the optical element and the stack and applying a pressure to press the optical element and the stack together. In one embodiment, the method also includes disposing a layer of a transparent bonding material between the stack and the optical element. The bonding method can be applied to a premade optical element or to a block of optical element material which is later formed or shaped into an optical element such as a lens or an optical concentrator.

Claims

1. A method of bonding a transparent optical element to a light emitting device having a stack of layers including semiconductor layers comprising an active region, the method comprising:

elevating a temperature of at least one of said optical element and said stack; and

applying a pressure to press said optical element and said stack together;

wherein the transparent optical element is directly connected to the stack of layers.

2. The method of claim 1, wherein said temperature is elevated to less than about 500°

C.

3. The method of claim 1, wherein said temperature is elevated to a temperature between about room temperature and about 1000°

C.

4. The method of claim 1, wherein elevating a temperature of at least one of said optical element and said stack comprises elevating a temperature of both said optical element and said stack.

5. The method of claim 1, wherein applying a pressure to press said optical element and said stack together comprises pressing said optical element and said stack together at a pressure between about 1 psi and 6000 psi.

6. The method of claim 1, wherein applying a pressure to press said optical element and said stack together comprises pressing said optical element and said stack together for a time between about 1 second and about 6 hours.

7. The method of claim 1, further comprising doping at least one of said optical element and said stack with a high diffusivity material.

8. The method of claim 7, wherein doping comprises doping during materials growth.

9. The method of claim 7, wherein doping comprises doping by implantation.

17. The method of claim 1, wherein said optical element is a transparent lens.

18. The method of claim 1, further comprising forming an antireflection coating on a surface of said optical element.

19. The method of claim 1, further comprising encapsulating said optical element and stack in one of epoxy and silicone.

20. The method of claim 1, further comprising beveling a surface of said stack.

21. The method of claim 20, further comprising coating said beveled surface with a reflective coating.

22. The method of claim 1, wherein a surface of said optical element pressed against said stack is perpendicular to a growth direction of said stack.

23. The method of claim 1, wherein a surface of said optical element pressed against said stack is parallel to a growth direction of said stack.

27. The method of claim 1 wherein the optical element comprises one or more luminescent materials, capable of converting a wavelength of light emitted by the stack of layers to at least another wavelength.

28. The method of claim 1 further comprising coating at least a portion of the optical element with one or more luminescent materials, capable of converting a wavelength of light emitted by the stack of layers to at least another wavelength.

10. A method of bonding a transparent optical element to a light emitting device having a stack of layers including semiconductor layers comprising an active region, the method comprising:

disposing a layer of a transparent bonding material between said optical element and a surface of said stack;

elevating a temperature of at least one of said optical element and said stack; and

applying a pressure to press said optical element and said stack together;

wherein the transparent bonding material has a refractive index greater than 1.5.

11. The method of claim 10, further comprising disposing one or more high diffusivity materials between said optical element and said stack.

12. The method of claim 10, wherein disposing a layer of a transparent bonding material comprises depositing the bonding material by a technique selected from the group of spinning, sputtering, evaporation, chemical vapor deposition, metal-organic chemical vapor deposition, vapor phase epitaxy, liquid phase epitaxy, and molecular beam epitaxy.

13. The method of claim 10, wherein said bonding material comprises an oxide of lead and an oxide of tungsten.

14. The method of claim 10, further comprising patterning the bonding material.

15. The method of claim 10, wherein said bonding material comprises an optical glass, and wherein said temperature is elevated to at least about a strain point temperature of said optical glass.

16. The method of claim 10, wherein the bonding layer comprises one or more luminescent materials, capable of converting a wavelength of light emitted by the stack of layers to at least another wavelength.

24. The method of claim 10, wherein the optical element comprises a material selected from the group of sapphire, SiC, zirconia oxide, GaN, AlN, GaP, ZnS, an oxide of lead, and an oxide of tungsten.

25. The method of claim 10 wherein the shape of the optical element is one of a dome, a paraboloid, a cone-shape, and a beveled shape.

26. The method of claim 10 wherein the stack comprises one of a substrate and a superstrate, said one of a substrate and a superstrate comprising a material selected from the group of sapphire, SiC, GaN, GaP, and ZnS.

29. A method of creating a light emitting device comprising a stack of layers including semiconductor layers and an optical element, said method comprising:

forming a block of optical element material having a substantially flat surface;

after forming the block of optical element having a substantially flat surface, bonding the substantially flat surface to said stack of layers including semiconductor layers; and

forming said block of transparent optical element material into said optical element.

30. The method of claim 29, wherein said bonding comprises:

elevating a temperature of said optical element and said stack; and

applying a pressure to press said optical element and said stack together.

31. The method of claim 29, wherein said forming said block of transparent optical element material into said optical element comprises an etching technique.

32. The method of claim 31, wherein said etching technique is selected from one of dry etching and wet etching.

33. The method of claim 31, wherein said etching is one of plasma etching, reactive ion etching, and chemically-assisted ion beam etching.

34. The method of claim 29, wherein said forming said block of transparent optical element material into said optical element comprises a lithographic technique.

35. The method of claim 34, wherein said lithographic technique is selected from a group consisting of photolithography, electron beam lithography, ion beam lithography, X-ray lithography, and holographic lithography.

36. The method of claim 29, wherein said forming said block of transparent optical element material into said optical element comprises a mechanical technique selected from a group consisting of milling, focused ion beam milling, ablating, machining, sawing, stamping, and scribing.

37. The method of claim 29, wherein said forming said block of transparent optical element material into said optical element comprises forming said optical element material into an optical concentrator.