Transparent mirrorless light emitting diode

• US 7,781,789 B2
• Filed: 11/15/2007
• Issued: 08/24/2010
• Est. Priority Date: 11/15/2006
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Nakamura, Shuji, DenBaars, Steven P., Speck, James S.
• Primary Examiner(s): Soward, Ida M
• Application Number:
  US11/940,898
• Publication Number:
  US 20080128731A1
• Time in Patent Office: 1,013 Days
• Field of Search: 257/88, 257 98-100, 257/E25.028, 257/E25.032, 257/E33.001, 257/E33.064, 257/E33.065, 257/E33.068, 257/E33.074, 257/E33.066, 438 34- 35
• US Class Current: 257/98
• CPC Class Codes: H01L 2224/16245 the item being metallic
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• 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 2224/48257 connecting the wire to a die pad of the item
• CPC Class Codes: H01L 2224/49109 outside the semiconductor or solid-state body
• 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 2924/00014 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 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/54 having a particular shape
• CPC Class Codes: H01L 33/60 Reflective elements

Abstract

An (Al, Ga, In)N light emitting diode (LED) in which multi-directional light can be extracted from one or more surfaces of the LED before entering a shaped optical element and subsequently being extracted to air. In particular, the (Al, Ga, In)N and transparent contact layers (such as ITO or ZnO) are embedded in or combined with a shaped optical element, which may be an epoxy, glass, silicon or other material molded into a sphere or inverted cone shape, wherein most of the light entering the inverted cone shape lies within a critical angle and is extracted. The present invention also minimizes internal reflections within the LED by eliminating mirrors and/or mirrored surfaces, in order to minimize re-absorption of the LED'"'"'s light by the emitting layer (or the active layer) of the LED. To assist in minimizing internal reflections, transparent electrodes, such as ITO or ZnO, may be used. Surface roughening by patterning or anisotropically etching (i.e., creating microcones) may also assist in light extraction, as well as minimizing internal reflections.

Claims

1. An opto-electronic device, comprising:

a light emitting diode (LED) that emits light out of the LED from multiple sides of the LED, wherein all layers of the LED are transparent for an emission wavelength except for an emitting layer.

2. The opto-electronic device of claim 1, wherein the light is emitted out of the LED from front and back sides of the LED.

3. The opto-electronic device of claim 1, wherein one or more layers of the LED are shaped, patterned, textured or roughened to increase the light extraction.

4. The opto-electronic device of claim 1, wherein the LED is comprised of multiple emitting layers of multiple wavelengths to generate light of a broader spectral range.

5. The opto-electronic device of claim 1, wherein the substrate is shaped, patterned, textured or roughened to increase the light extraction.

6. The opto-electronic device of claim 1, wherein the LED resides in a lead frame that allows the light to be extracted from two or more sides of the LED.

7. The opto-electronic device of claim 1, wherein the LED includes a transparent substrate.

8. The opto-electronic device of claim 7, wherein the transparent substrate is electrically conductive.

9. The opto-electronic device of claim 1, wherein the LED includes one or more transparent contact layers.

10. The opto-electronic device of claim 9, wherein the transparent contact layer is shaped, patterned, textured or roughened to increase the light extraction.

11. The opto-electronic device of claim 9, wherein a current spreading layer is deposited on the LED before the transparent contact layer.

12. The opto-electronic device of claim 1, wherein the LED is embedded within a shaped optical element.

13. The opto-electronic device of claim 12, wherein the shaped optical element is a molding.

14. The opto-electronic device of claim 13, wherein the shaped optical element is shaped, patterned, textured or roughened to increase the light extraction.

15. The opto-electronic device of claim 12, wherein the shaped optical element is comprised of transparent materials.

16. The opto-electronic device of claim 12, wherein the shaped optical element is an inverted cone shape.

17. The opto-electronic device of claim 12, wherein a mirror is placed inside the shaped optical element.

18. The opto-electronic device of claim 12, wherein a phosphor layer is located on top of the shaped optical element, within the shaped optical element or near a surface of the shaped optical element.

19. The opto-electronic device of claim 18, wherein the phosphor layer is shaped, patterned, textured or roughened to increase the light extraction.

20. The opto-electronic device of claim 12, wherein the shaped optical element is a sphere shape.

24. The opto-electronic device of claim 17, wherein the shaped optical element is comprised of transparent materials.

21. An opto-electronic device comprising:

a light emitting diode (LED) that emits light out of the LED from multiple sides of the LED, wherein the LED is embedded within a shaped optical element, the shaped optical element is an inverted cone shape, and the light is reflected to a front surface of the inverted cone shape by side walls of the inverted cone shape positioned at a critical angle, so that the light is emitted through the front surface of the inverted cone shape.

22. The opto-electronic device of claim 21, wherein the shaped optical element is a molding.

23. The opto-electronic device of claim 21, wherein the shaped optical element is shaped, patterned, textured or roughened to increase the light extraction.

25. The opto-electronic device of claim 21, wherein a mirror is placed inside the shaped optical element.

26. The opto-electronic device of claim 21, wherein a phosphor layer is located on top of the shaped optical element, within the shaped optical element or near a surface of the shaped optical element.

27. The opto-electronic device of claim 26, wherein the phosphor layer is shaped, patterned, textured or roughened to increase the light extraction.

28. An opto-electronic device, comprising:

a light emitting diode (LED) that emits light out of the LED from multiple sides of the LED, wherein the LED resides on a transparent plate in a lead frame that allows the light to be extracted from two or more sides of the LED.

29. A method of fabricating an opto-electronic device, comprising:

creating a light emitting diode (LED) that emits light out of the LED from multiple sides of the LED, wherein all layers of the LED are transparent for an emission wavelength except for an emitting layer.

30. The method of claim 29, wherein the light is emitted out of the LED from front and back sides of the LED.

31. The method of claim 29, wherein one or more layers of the LED are shaped, patterned, textured or roughened to increase the light extraction.

32. The method of claim 29, wherein the LED is comprised of multiple emitting layers of multiple wavelengths to generate light of a broader spectral range.

33. The method of claim 29, wherein the substrate is shaped, patterned, textured or roughened to increase the light extraction.

34. The method of claim 29, wherein the LED resides in a lead frame that allows the light to be extracted from two or more sides of the LED.

35. The method of claim 29, wherein the LED includes a transparent substrate.

36. The method of claim 35, wherein the transparent substrate is electrically conductive.

37. The method of claim 29, wherein the LED includes one or more transparent contact layers.

38. The method of claim 37, wherein the transparent contact layer is shaped, patterned, textured or roughened to increase the light extraction.

39. The method of claim 37, wherein a current spreading layer is deposited on the LED before the transparent contact layer.

40. The method of claim 29, wherein the LED is embedded within a shaped optical element.

41. The method of claim 40, wherein the shaped optical element is a molding.

42. The method of claim 41, wherein the shaped optical element is shaped, patterned, textured or roughened to increase the light extraction.

43. The method of claim 40, wherein the shaped optical element is comprised of transparent materials.

44. The method of claim 40, wherein the shaped optical element is a sphere shape.

45. The method of claim 40, wherein the shaped optical element is an inverted cone shape.

46. The method of claim 40, wherein a mirror is placed inside the shaped optical element.

47. The method of claim 40, wherein a phosphor layer is located on top of the shaped optical element, within the shaped optical element or near a surface of the shaped optical element.

48. The method of claim 47, wherein the phosphor layer is shaped, patterned, textured or roughened to increase the light extraction.

49. A method of fabricating an opto-electronic device, comprising:

creating a light emitting diode (LED) that emits light out of the LED from multiple sides of the LED, wherein the LED is embedded within a shaped optical element, the shaped optical element is an inverted cone shape, and the light is reflected to a front surface of the inverted cone shape by side walls of the inverted cone shape positioned at a critical angle, so that the light is emitted through the front surface of the inverted cone shape.

50. The method of claim 49, wherein the shaped optical element is a molding.

51. The method of claim 49, wherein the shaped optical element is shaped, patterned, textured or roughened to increase the light extraction.

52. The method of claim 49, wherein the shaped optical element is comprised of transparent materials.

53. The method of claim 49, wherein a mirror is placed inside the shaped optical element.

54. The method of claim 49, wherein a phosphor layer is located on top of the shaped optical element, within the shaped optical element or near a surface of the shaped optical element.

55. The method of claim 54, wherein the phosphor layer is shaped, patterned, textured or roughened to increase the light extraction.

56. A method of of fabricating an opto-electronic device, comprising:

creating a light emitting diode (LED) that emits light out of the LED from multiple sides of the LED, wherein the LED resides on a transparent plate in a lead frame that allows the light to be extracted from two or more sides of the LED.