TRANSPARENT LIGHT EMITTING DIODES

• US 20140353707A1
• Filed: 08/15/2014
• Published: 12/04/2014
• Est. Priority Date: 06/03/2004
• 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
• Granted Patent: US 10,217,916 B2
• Time in Patent Office: Days
• 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 lead frame having a transparent plate; and

a light emitting diode (LED) chip, placed on or above the transparent plate in the lead frame, emitting light through at least front and back sides of the LED chip;

wherein the transparent plate in the lead frame allows the light emitted from the LED chip to be extracted out of the LED chip from the front or back side of the LED chip.

2. The device of claim 1, wherein a side of the LED chip adjacent the transparent plate is roughened, textured or patterned, to increase extraction of the light emitted from the LED chip through the transparent plate in the lead frame.

3. The device of claim 2, wherein the side of the LED chip adjacent the transparent plate that is roughened, textured or patterned comprises a surface of a p-type layer of the LED chip.

4. The device of claim 2, wherein the side of the LED chip adjacent the transparent plate that is roughened, textured or patterned comprises a surface of an n-type layer of the LED chip.

5. The device of claim 1, wherein the LED chip includes a transparent substrate and the transparent substrate is adjacent the transparent plate.

6. The device of claim 5, wherein the transparent substrate is roughened, textured, or patterned, to increase extraction of the light emitted from the LED chip through the transparent plate in the lead frame.

7. The device of claim 5, wherein the transparent substrate is a patterned sapphire substrate (PSS) that increases extraction of the light emitted from the LED chip through an interface between the LED chip and patterned sapphire substrate.

8. The device of claim 1, wherein the transparent plate is roughened, textured or patterned, to increase extraction of the light emitted from the LED chip through the transparent plate in the lead frame.

9. The device of claim 1, wherein the LED chip is embedded with or contained in a molding or shaped optical element that is transparent to the light emitted from the LED chip, and a phosphor layer is formed within, near a surface of, or on top of, the molding or shaped optical element, for wavelength conversion of the light emitted from the LED chip.

10. The device of claim 9, wherein at least a portion of the phosphor layer is roughened, textured, or patterned, to minimize internal reflection of the light within the phosphor layer.

11. The device of claim 9, further comprising a mirror, placed outside of the molding or shaped optical element, in order to obtain more of the light emitted from at least one side of the LED chip, wherein the mirror'"'"'s shape prevents reflected light from reaching the LED chip, in order to reduce re-absorption of the light by the LED chip.

12. The device of claim 1, further comprising at least one transparent contact layer deposited on a surface of the LED chip that is shaped, patterned, textured or roughened to increase extraction of the light emitted from the LED chip.

13. The device of claim 1, wherein the LED chip is comprised of 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.

14. A method for fabricating a light emitting device, comprising:

providing a lead frame having a transparent plate; and

placing a light emitting diode (LED) chip on or above the transparent plate in the lead frame;

wherein light is emitted through at least front and back sides of the LED chip; and

wherein the transparent plate in the lead frame allows the light emitted from the LED chip to be extracted out of the LED chip from the front or back side of the LED chip.

15. The method of claim 14, wherein a side of the LED chip adjacent the transparent plate is roughened, textured or patterned, to increase extraction of the light emitted from the LED chip through the transparent plate in the lead frame.

16. The method of claim 15, wherein the side of the LED chip adjacent the transparent plate that is roughened, textured or patterned comprises a surface of a p-type layer of the LED chip.

17. The method of claim 15, wherein the side of the LED chip adjacent the transparent plate that is roughened, textured or patterned comprises a surface of an n-type layer of the LED chip.

18. The method of claim 14, wherein the LED chip includes a transparent substrate and the transparent substrate is adjacent the transparent plate.

19. The method of claim 18, wherein the transparent substrate is roughened, textured, or patterned, to increase extraction of the light emitted from the LED chip through the transparent plate in the lead frame.

20. The method of claim 18, wherein the transparent substrate is a patterned sapphire substrate (PSS) that increases extraction of the light emitted from the LED chip through an interface between the LED chip and patterned sapphire substrate.

21. The method of claim 14, wherein the transparent plate is roughened, textured or patterned, to increase extraction of the light emitted from the LED chip through the transparent plate in the lead frame.

22. The method of claim 14, wherein the LED chip is embedded with or contained in a molding or shaped optical element that is transparent to the light emitted from the LED chip, and a phosphor layer is formed within, near a surface of, or on top of, the molding or shaped optical element, for wavelength conversion of the light emitted from the LED chip.

23. The method of claim 22, wherein at least a portion of the phosphor layer is roughened, textured, or patterned, to minimize internal reflection of the light within the phosphor layer.

24. The method of claim 22, further comprising placing a mirror outside of the molding or shaped optical element, in order to obtain more of the light emitted from at least one side of the LED chip, wherein the mirror'"'"'s shape prevents reflected light from reaching the LED chip, in order to reduce re-absorption of the light by the LED chip.

25. The method of claim 14, further comprising depositing at least one transparent contact layer on a surface of the LED chip that is shaped, patterned, textured or roughened to increase extraction of the light emitted from the LED chip.

26. The method of claim 14, wherein the LED chip is comprised of 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.