Transparent light emitting diodes

• US 8,294,166 B2
• Filed: 12/11/2007
• Issued: 10/23/2012
• 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:
  US11/954,154
• Publication Number:
  US 20080149959A1
• Time in Patent Office: 1,778 Days
• Field of Search: 257/9, 257/99, 257/100, 257/14, 257/95, 257/98, 257/E29.072, 257/E29.076, 257/E33.008, 257/E31.033, 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 device, comprising:

a light emitting diode (LED) including a plurality of III-nitride layers, wherein;

the plurality of the III-nitride layers include an n-type layer, a p-type layer, and an active region between the n-type layer and the p-type layer that emits light, and

an n-type side of the LED is on a front side of the LED, and a p-type side of the LED is on a back side of the LED opposite the front side;

a transparent substrate or sub-mount attached to the p-type side of the III-nitride layers only; and

one or more shaped optical elements combined with the LED and the transparent substrate or sub-mount, wherein the shaped optical elements and the transparent substrate or sub-mount extract light from the LED, such that the light is extracted through at least the front side and the back side of the LED.

2. The device of claim 1, wherein one or more transparent conducting layers are positioned to electrically connect the III-nitride layers.

3. The device of claim 2, wherein one or more current spreading layers are deposited on the III-nitride layers, and the transparent conducting layers are deposited on the current spreading layers.

4. The device of claim 1, without mirrors or mirrored surfaces on the front side or the back side of the LED.

5. The device of claim 1, wherein a surface of one or more of the III-nitride layers is roughened, textured, patterned or shaped to enhance light extraction.

6. The device of claim 1, wherein a lead frame supports the III-nitride layers and the light emitted from the III-nitride layers is transmitted through the lead frame.

7. The device of claim 6, wherein the III-nitride layers reside on a transparent plate in the lead frame, and the light emitted from the III-nitride layers is transmitted through the transparent plate in the lead frame.

8. The device of claim 1, wherein the III-nitride layers are embedded in the shaped optical elements, and the light is extracted from a plurality of surfaces of the III-nitride layers before entering the shaped optical elements and subsequently being extracted.

9. The device of claim 8, wherein at least a portion of the light entering the shaped optical elements lies within a critical angle and is extracted.

10. The device of claim 8, wherein one or more surfaces of the shaped optical elements are roughened, textured, patterned or shaped to enhance light extraction.

11. The device of claim 8, wherein at least one of the shaped optical elements includes a phosphor layer.

12. The device of claim 11, wherein one or more surfaces of the phosphor layer is roughened, textured, patterned or shaped to enhance light extraction.

13. The device of claim 8, wherein the shaped optical elements have an inverted cone shape.

14. The device of claim 13, wherein the III-nitride layers are positioned within the inverted cone shape such that the light is reflected by sidewalls of the inverted cone shape.

15. The device of claim 1, wherein an insulating layer covering the III-nitride layers is partially removed, and a conductive layer is deposited within a hole or depression in the surface of the insulating layer to make electrical contact with the III-nitride layers.

16. The device of claim 1, wherein the III-nitride layers are wafer bonded to the transparent substrate or sub-mount-and light is extracted through the transparent substrate or sub-mount.

17. The device of claim 16, wherein the transparent substrate or sub-mount is electrically conductive.

18. The device of claim 17, wherein the III-nitride layers are wafer bonded with the transparent substrate or sub-mount using a transparent glue, a transparent epoxy, or other transparent material.

19. The device of claim 18, wherein the transparent glue, transparent epoxy, or other transparent material is electrically conductive.

20. The LED of claim 1, wherein the LED reduces re-absorption of the light by the active region and extracts the light more effectively as compared to an LED that has a mirror at its back side, so that light emitted by an active region, of the LED that has the mirror, and towards the mirror, is reflected for extraction at a front side of the LED that has the mirror.

21. The device of claim 1, wherein the shaped optical elements and the transparent substrate or sub-mount extract light from the LED, such that the light is extracted through at least the front side and the back side of the LED while reducing re-absorption of the light by the active region.

22. A method of fabricating a device, comprising:

forming a Light Emitting Diode (LED), wherein the LED comprises;

a plurality of III-nitride layers including an n-type layer, a p-type layer, and an active region between the n-type layer and the p-type layer that emits light, and

an n-type side of the LED is on a front side of the LED, and a p-type side of the LED is on a back side of the LED opposite the front side;

attaching a transparent substrate or sub-mount to a p-type side of the III-nitride layers only; and

forming one or more shaped optical elements combined with the LED and the transparent substrate or sub-mount, wherein the shaped optical elements and the transparent substrate or sub-mount extract light from the LED, such that the light is extracted through at least the front side and the back side of the LED.

23. The method of claim 22, wherein one or more transparent conducting layers are positioned to electrically connect the III-nitride layers.

24. The method of claim 23, wherein one or more current spreading layers are deposited on the III-nitride layers, and the transparent conducting layers are deposited on the current spreading layers.

25. The method of claim 22, wherein mirrors or mirrored surfaces are not formed on the front side or the back side of the LED.

26. The method of claim 22, wherein an insulating layer covering the III-nitride layers is partially removed, and a conductive layer is deposited within a hole or depression in the surface of the insulating layer to make electrical contact with the III-nitride layers.

27. The method of claim 22, wherein the LED reduces re-absorption of the light by the active region and extracts the light more effectively as compared to an LED that has a mirror at its back side, so that light emitted by an active region, of the LED that has the mirror, and towards the mirror, is reflected for extraction at a front side of the LED that has the mirror.

28. The method of claim 22, wherein a surface of one or more of the III-nitride layers is roughened, textured, patterned or shaped to enhance light extraction.

29. The method of claim 22, wherein a lead frame supports the III-nitride layers and the light emitted from the III-nitride layers is transmitted through the transparent plate in the lead frame.

30. The method of claim 29, wherein the III-nitride layers reside on a transparent plate in the lead frame, and the light emitted from the III-nitride layers is transmitted through the transparent plate in the lead frame.

31. The method of claim 22, wherein the III-nitride layers are embedded in the shaped optical elements, and the light is extracted from a plurality of surfaces of the III-nitride layers before entering the shaped optical element and subsequently being extracted.

32. The method of claim 31, wherein at least a portion of the light entering the shaped optical element lies within a critical angle and is extracted.

33. The method of claim 31, wherein one or more surfaces of the shaped optical element is roughened, textured, patterned or shaped to enhance light extraction.

34. The method of claim 31, wherein at least one of the shaped optical elements includes a phosphor layer.

35. The method of claim 34, wherein one or more surfaces of the phosphor layer is roughened, textured, patterned or shaped to enhance light extraction.

36. The method of claim 31, wherein the shaped optical elements have an inverted cone shape.

37. The method of claim 36, wherein the III-nitride layers are positioned within the inverted cone shape such that the light is reflected by sidewalls of the inverted cone shape.

38. The method of claim 22, wherein the III-nitride layers are wafer bonded to the transparent substrate or sub-mount and light is extracted through the transparent substrate or sub-mount.

39. The method of claim 38, wherein the transparent substrate or sub-mount is electrically conductive.

40. The method of claim 39, wherein the III-nitride layers are wafer bonded with the transparent substrate or sub-mount using a transparent glue, a transparent epoxy, or other transparent material.

41. The method of claim 40, wherein the transparent glue, transparent epoxy, or other transparent material is electrically conductive.

42. The method of claim 22, wherein the shaped optical elements and the transparent substrate or sub-mount extract light from the LED, such that the light is extracted through at least the front side and the back side of the LED while reducing re-absorption of the light by the active region.