Transparent light emitting diodes

• US 8,835,959 B2
• Filed: 09/19/2012
• Issued: 09/16/2014
• Est. Priority Date: 12/11/2006
• 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., Asamizu, Hirokuni
• Primary Examiner(s): Arroyo, Teresa M
• Application Number:
  US13/622,884
• Publication Number:
  US 20130020602A1
• Time in Patent Office: 727 Days
• Field of Search: 257/95, 257/98, 257/103, 257/E33.067, 257/E33.07, 257/E33.074
• US Class Current: 257/98
• CPC Class Codes: G02B 19/0028 refractive and reflective surfaces, e.g. non-imaging catadioptric systems
• CPC Class Codes: G02B 19/0061 the light source comprising a LED semiconductor devices with at least one potential-jump barrier or surface barrier specially adapted for light emission H01L33/00
• CPC Class Codes: H01L 2224/0554 External layer
• CPC Class Codes: H01L 2224/0555 Shape
• CPC Class Codes: H01L 2224/0556 Disposition
• CPC Class Codes: H01L 2224/05568 the whole external layer protruding from the surface
• CPC Class Codes: H01L 2224/05573 Single external layer
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/16245 the item being metallic
• 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 2224/49107 on the semiconductor or solid-state body
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• 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 2924/1815 Shape
• CPC Class Codes: H01L 2933/0091 Scattering means in or on the semiconductor body or semiconductor body package H01L33/22 takes precedence
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/387 with a plurality of electrode regions in direct contact with the semiconductor body and being electrically interconnected by another electrode layer
• CPC Class Codes: H01L 33/54 having a particular shape
• CPC Class Codes: H01L 33/58 : Optical field-shaping elements
• 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

A transparent light emitting diode (LED) includes a plurality of III-nitride layers, including an active region that emits light, wherein all of the layers except for the active region are transparent for an emission wavelength of the light, such that the light is extracted effectively through all of the layers and in multiple directions through the layers. Moreover, the surface of one or more of the III-nitride layers may be roughened, textured, patterned or shaped to enhance light extraction.

Claims

1. A light emitting device, comprising:

a sub-mount or lead-frame;

a III-nitride light emitting diode (LED) mounted on the sub-mount or lead frame via a first surface of the LED, wherein light from the LED is extracted from at least the first surface through the sub-mount or lead frame and a second surface of the LED opposite the first surface; and

a first shaped optical element receiving the light extracted from the first surface, wherein the light is extracted out of the first shaped optical element; and

a second shaped optical element receiving the light extracted from the second surface, wherein the light is extracted out of the second shaped optical element;

wherein the first and second shaped optical elements comprise inverted cone shapes and the light is extracted through emitting surfaces of the inverted cone shapes.

2. The device of claim 1, wherein mirrors or mirrored surfaces are eliminated from, or not attached to, the LED, to minimize internal reflections in order to minimize re-absorption of the light by an active region of the LED.

3. The device of claim 2, wherein at least one of the first surface and the second surface of the LED is roughened, textured, patterned or shaped to enhance light extraction.

4. The device of claim 3, wherein the LED is embedded in or combined with the first or second shaped optical element.

5. The device of claim 4, wherein one or more surfaces of the first or second shaped optical element are roughened, textured, patterned or shaped to enhance extraction of the light.

6. The device of claim 5, wherein the first or second shaped optical element includes a phosphor layer.

7. The device of claim 6, wherein one or more surfaces of the phosphor layer are roughened, textured, patterned or shaped to enhance light extraction.

8. The device of claim 1, wherein the LED is embedded in one of the inverted cone shapes such that a front surface and a back surface of the inverted cone shape are parallel to sidewalls of the LED, and the light is extracted through the front surface of the inverted cone shape.

9. The device of claim 8, further comprising one or more mirrors within the first or second shaped optical element to reflect the light from the first surface and second surface of the LED towards an emitting surface of the first or second shaped optical element.

10. The device of claim 1, wherein sidewalls of at least one of the inverted cone shapes are at a critical angle, for the light, with respect to a base of the inverted cone shape.

11. The device of claim 1, further comprising a mirror below the sub-mount or lead frame, or within the first or second shaped optical element, wherein the mirror guides the light extracted from the second surface away from the LED and into the first or second shaped optical element to increase light extraction from one or more top sides of the LED.

12. The device of claim 1, wherein the first or second shaped optical element comprises glass.

13. The device of claim 1, further comprising one or more Zinc Oxide or Indium Tin Oxide layers positioned to electrically connect the sub mount or lead frame to the LED.

14. The device of claim 1, wherein the first or second shaped optical element comprises epoxy.

15. A method of fabricating a light emitting device, comprising:

mounting a III-nitride light emitting diode (LED) on a sub-mount or lead frame via a first surface of the LED, wherein light from the LED is extracted from at least the first surface through the sub-mount or lead frame and a second surface of the LED opposite the first surface; and

attaching a first shaped optical element to the LED, wherein the first shaped optical element receives the light extracted from the first surface and the light is extracted out of the first shaped optical element; and

attaching a second shaped optical element to the LED, wherein the second shaped optical element receives the light extracted from the second surface, and the light is extracted out of the second shaped optical element;

wherein the first and second shaped optical elements comprise inverted cone shapes and the light is extracted through emitting surfaces of the inverted cone shapes.

16. The method of claim 15, wherein mirrors or mirrored surfaces are eliminated from, or not attached to, the LED, to minimize internal reflections in order to minimize re-absorption of the light by an active region of the LED.

17. The method of claim 16, wherein at least one of the first surface and the second surface of the LED is roughened, textured, patterned or shaped to enhance light extraction.

18. The method of claim 17, wherein the LED is embedded in or combined with the first or second shaped optical element.

19. The method of claim 18, wherein one or more surfaces of the first or second shaped optical element are roughened, textured, patterned or shaped to enhance extraction of the light.

20. The method of claim 19, wherein the first or second shaped optical element includes a phosphor layer.

21. The method of claim 20, wherein one or more surfaces of the phosphor layer are roughened, textured, patterned or shaped to enhance light extraction.

22. The method of claim 15, wherein the LED is embedded in one of the inverted cone shapes such that a front surface and a back surface of the inverted cone shape are parallel to sidewalls of the LED, and the light is extracted through the front surface of the inverted cone shape.

23. The method of claim 22, further comprising including one or more mirrors within the first or second shaped optical element to reflect the light from the first surface and second surface of the LED towards an emitting surface of the first or second shaped optical element.

24. The method of claim 15, wherein sidewalls of at least one of the inverted cone shapes are at a critical angle, for the light, with respect to a base of the inverted cone shape.

25. The method of claim 15, further comprising including a mirror below the sub-mount or lead frame, or within the first or second shaped optical element, wherein the mirror guides the light extracted from the second surface away from the LED and into the first or second shaped optical element to increase light extraction from one or more top sides of the LED.

26. The method of claim 15, wherein the first or second shaped optical element comprises glass.

27. The method of claim 15, further comprising positioning one or more Zinc Oxide or Indium Tin Oxide layers to electrically connect the sub mount or lead frame to the LED.

28. The method of claim 15, wherein the first or second shaped optical element comprises epoxy.