Standing transparent mirrorless light emitting diode

• US 7,687,813 B2
• Filed: 11/15/2007
• Issued: 03/30/2010
• 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: DenBaars, Steven P., Nakamura, Shuji
• Primary Examiner(s): COLEMAN, WILLIAM D
• Application Number:
  US11/940,883
• Publication Number:
  US 20080111146A1
• Time in Patent Office: 866 Days
• Field of Search: 257/95, 257/98, 257/E33.059, 438/27
• US Class Current: 257/95
• 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 2224/48237 connecting the wire to a die pad of the item
• 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 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• 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 2924/181 Encapsulation
• 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 33/507 the elements being in intimate contact with parts other than the semiconductor body or integrated with parts other than the semiconductor body
• CPC Class Codes: H01L 33/54 having a particular shape
• 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

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 comprising an epoxy, glass, silicon or other material molded into an inverted cone shape, wherein most of the light entering the inverted cone shape lies within a critical angle and is extracted. In addition, the present invention stands the LED on end, i.e., rotates the position of the LED within the shaped optical element by approximately 90° as compared to a conventional LED, in order to extract light more effectively from the LED. 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 shaped optical element; and

a light emitting diode (LED) embedded in the shaped optical element, wherein light is emitted from the LED in a direction substantially perpendicular to a direction that light is emitted from the shaped optical element, wherein the LED resides on a transparent plate in a lead frame that allows the light to be extracted from multiple sides of the LED.

2. The opto-electronic device of claim 1, wherein an emitting surface of the LED is substantially perpendicular to an emitting surface of the shaped optical element.

3. The opto-electronic device of claim 1, wherein the light is emitted from the shaped optical element in a direction parallel to a plane of the LED'"'"'s epitaxial layers.

4. The opto-electronic device of claim 1, wherein the shaped optical element comprises an inverted cone shape.

5. The opto-electronic device of claim 1, wherein the shaped optical element is comprised of transparent materials.

6. The opto-electronic device of claim 1, wherein the shaped optical element is shaped, patterned, textured or roughened to increase the light'"'"'s extraction from the shaped optical element.

7. The opto-electronic device of claim 1, further comprising a phosphor layer located on or in the shaped optical element.

8. The opto-electronic device of claim 1, wherein all layers of the LED are transparent for an emission wavelength except for an emitting layer.

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 1, wherein the LED includes a transparent substrate.

11. The opto-electronic device of claim 4, wherein the inverted cone shape has side walls positioned at an angle to the inverted cone shape'"'"'s base, wherein the angle is more than sin⁻

1(n₁/n₂), n₁ is a refractive index of air, and n₂ is a refractive index of the material of the inverted cone shape.

12. The opto-electronic device of claim 11, wherein the light is reflected to a top surface of the inverted cone shape by the side walls of the inverted cone shape for emission through the top surface of the inverted cone shape.

13. The opto-electronic device of claim 7, wherein the phosphor layer is shaped, patterned, textured or roughened to increase the light'"'"'s extraction through the phosphor layer.

14. The opto-electronic device of claim 9, wherein the transparent contact layers are shaped, patterned, textured or roughened to increase the light'"'"'s extraction.

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

16. The opto-electronic device of claim 10, wherein the transparent substrate is shaped, patterned, textured or roughened to increase the light'"'"'s extraction.

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

embedding a light emitting diode (LED) in a shaped optical element, wherein light is emitted from the LED in a direction substantially perpendicular to a direction that light is emitted from the shaped optical element, wherein the LED resides on a transparent plate in a lead frame that allows the light to be extracted from multiple sides of the LED.

18. The method of claim 17, wherein an emitting surface of the LED is substantially perpendicular to an emitting surface of the shaped optical element.

19. The method of claim 17, wherein the light is emitted from the shaped optical element in a direction parallel to a plane of the LED'"'"'s epitaxial layers.

20. The method of claim 17, wherein the shaped optical element comprises an inverted cone shape.

21. The method of claim 17, wherein the shaped optical element is comprised of transparent materials.

22. The method of claim 17, wherein the shaped optical element is shaped, patterned, textured or roughened to increase the light'"'"'s extraction from the shaped optical element.

23. The method of claim 17, further comprising forming a phosphor layer on or in the shaped optical element.

24. The method of claim 17, wherein all layers of the LED are transparent for an emission wavelength except for an emitting layer.

25. The method of claim 17, wherein the LED includes one or more transparent contact layers.

26. The method of claim 17, wherein the LED includes a transparent substrate.

27. The method of claim 20, wherein the inverted cone shape has side walls positioned at an angle to the inverted cone shape'"'"'s base, wherein the angle is more than sin⁻

1(n₁/n₂), n₁ is a refractive index of air, and n₂ is a refractive index of the material of the inverted cone shape.

28. The method of claim 27, wherein the light is reflected to a top surface of the inverted cone shape by the side walls of the inverted cone shape for emission through the top surface of the inverted cone shape.

29. The method of claim 23, wherein the phosphor layer is shaped, patterned, textured or roughened to increase the light'"'"'s extraction through the phosphor layer.

30. The method of claim 25, wherein the transparent contact layers are shaped, patterned, textured or roughened to increase the light'"'"'s extraction.

31. The method of claim 25, wherein a current spreading layer is deposited on the LED before the transparent contact layers.

32. The method of claim 26, wherein the transparent substrate is shaped, patterned, textured or roughened to increase the light'"'"'s extraction.