TRANSPARENT LIGHT EMITTING DIODES

• US 20130020602A1
• Filed: 09/19/2012
• Published: 01/24/2013
• 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: DenBaars, Steven P., Nakamura, Shuji, Asamizu, Hirokuni
• Granted Patent: US 8,835,959 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 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 and the second surface of the LED; and

a shaped optical element receiving the light extracted from the first surface and the second surface and extracting the light out of the shaped optical element.

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 a 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 in the shaped optical element.

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

6. The device of claim 5, wherein the 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 shaped optical element comprises one or more cones or truncated cones.

9. The device of claim 8, further comprising one of the truncated cones on the first surface and one of the truncated cones on the second surface of the LED, wherein the light is extracted through front surfaces of the truncated cones.

10. The device of claim 8, wherein the LED is embedded in the truncated cone such that a front surface and back surface of the truncated cone are parallel to sidewalls of the LED, and the light is extracted through the front surface of the shaped optical element.

11. The device of claim 10, further comprising mirrors within the shaped optical element to reflect the light from the first surface and second surface of the LED towards a front surface of the shaped optical element.

12. The device of claim 8, wherein sidewalls of each truncated cone are at a critical angle, for the light, with respect to a base of the truncated cone.

13. The device of claim 1, wherein the shaped optical element comprises a sphere or ellipsoid.

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

15. The device of claim 1, wherein the shaped optical element comprises glass.

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

17. The device of claim 1, wherein the shaped optical element comprises epoxy.

18. 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 and the second surface of the LED; and

attaching a shaped optical element to the LED, wherein the shaped optical element receives the light extracted from the first surface and the second surface and extracts the light out of the shaped optical element.