LIGHT EMITTING DIODE WITH IMPROVED LUMINOUS EFFICIENCY

• US 20120049223A1
• Filed: 08/15/2011
• Published: 03/01/2012
• Est. Priority Date: 08/27/2010
• Status: Active Grant

• Current Assignee: Seoul Viosys Co., Ltd. (Seoul Semiconductor Co., Ltd.)
• Original Assignee: Seoul Optodevice Company Limited (Seoul Semiconductor Co., Ltd.)
• Inventors: YANG, Jeong Hee, KIM, Kyoung Wan, YOON, Yeo Jin, KIM, Ye Seul, OH, Sang Hyun, SUH, Duk Il, LEE, Keum Ju, LEE, Jin Woong, JEONG, Da Yeon
• Granted Patent: US 8,878,220 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• 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 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/38 with a particular shape
• CPC Class Codes: H01L 33/385 the electrode extending at least partially onto a side surface of the semiconductor body
• CPC Class Codes: H01L 33/42 Transparent materials

Abstract

Exemplary embodiments of the present invention relate to light emitting diodes. A light emitting diode according to an exemplary embodiment of the present invention includes a substrate having a first side edge and a second side edge, and a light emitting structure arranged on the substrate. The light emitting structure includes a first conductivity-type semiconductor layer, an active layer, and a second conductivity-type semiconductor layer. A transparent electrode layer including a concave portion and a convex portion is arranged on the second conductivity-type semiconductor layer. A first electrode pad contacts an upper surface of the first conductivity-type semiconductor layer and is located near a center of the first side edge. Two second electrode pads are located near opposite distal ends of the second side edge to supply electric current to the second conductivity-type semiconductor layer. A first pad extension extends from the first electrode pad and a second pad extension extends from each of the two second electrode pads.

Claims

1. A light emitting diode, comprising:

a substrate comprising a first side edge and a second side edge;

a light emitting structure arranged on the substrate, the light emitting structure comprising a first conductivity-type semiconductor layer, an active layer, and a second conductivity-type semiconductor layer;

a transparent electrode layer arranged on the second conductivity-type semiconductor layer;

a first electrode pad contacting an upper surface of the first conductivity-type semiconductor layer, the first electrode pad located near a center of the first side edge;

two second electrode pads located near opposite distal ends of the second side edge, the two second electrode pads to supply electric current to the second conductivity-type semiconductor layer;

a first pad extension extending from the first electrode pad; and

a second pad extension extending from each of the two second electrode pads, the second pad extension contacting an upper surface of the transparent electrode layer.

2. The light emitting diode of claim 1, wherein the first pad extension comprises:

a first inserting portion extending from the first electrode pad towards the second side edge; and

second inserting portions extending from a portion of the first inserting portion between a central region of the first inserting portion and the first electrode pad towards opposite sides of the first inserting portion along the first side edge, the second inserting portions being bent to extend towards the second side edge, and being further bent to extend toward each other and to terminate such that distal ends of the second inserting portions do not contact each other,

wherein the second pad extension comprises;

a connecting portion connecting the two second electrode pads to each other therethrough;

a first inserting portion extending from a central region of the connecting portion towards the first electrode pad;

second inserting portions extending from a distal end of the first inserting portion along the second side edge, the second inserting portions being bent to surround a distal end of the first pad extension first inserting portion and extending towards the first side edge; and

a third inserting portion extending from each of the two electrode pads towards the first side edge and being bent to extend towards the first electrode pad along the first side edge.

3. The light emitting diode of claim 2, wherein the first pad extension first inserting portion is collinear with the second pad extension first inserting portion, and each of the second pad extension second inserting portions are respectively located between the first inserting portion and the second inserting portions of the first pad extension.

4. The light emitting diode of claim 1, wherein the transparent electrode layer comprises nanoparticles and an upper transparent electrode layer covering the nanoparticles, and wherein the upper transparent electrode layer comprises a convex-concave surface.

5. The light emitting diode of claim 4, wherein the nanoparticles comprise a rounded surface.

6. The light emitting diode of claim 1, further comprising an insulation layer covering the transparent electrode layer, wherein the insulation layer comprises a convex-concave surface.

7. The light emitting diode of claim 1, further comprising micro-lenses,

wherein the transparent electrode layer comprises blind holes or through-holes and the micro-lenses are arranged in the holes.

8. The light emitting diode of claim 7, wherein the micro-lenses comprise a material having a lower refractive index than the transparent electrode layer.

9. The light emitting diode of claim 8, wherein the micro-lenses comprise SiO₂.

10. The light emitting diode of claim 7, wherein the micro-lenses comprise a vertical cross-section, a width of which gradually decreases in a direction away from the substrate.

11. The light emitting diode of claim 7, wherein the micro-lenses comprise a vertical cross-section, which comprises at least two inclined surfaces with an obtuse angle defined therebetween.

12. The light emitting diode of claim 7, wherein the micro-lenses comprise a horizontal cross-section of a circular shape, an elliptical shape, a hexagonal shape, a rectangular shape, or a triangular shape.

13. A method of fabricating a light emitting diode (LED), the method comprising:

forming epitaxial layers on a substrate, the epitaxial layers comprising a first conductivity-type semiconductor layer, an active layer, and a second conductivity-type semiconductor layer;

etching the epitaxial layers to expose first regions of the first conductivity-type semiconductor layer;

forming a lower transparent electrode layer on the epitaxial layers;

etching the lower transparent electrode layer to form nanoparticles on the second conductivity-type semiconductor layer;

forming an upper transparent electrode layer to cover the nanoparticles;

forming a first electrode pad and first pad extensions on the first regions of the first conductivity-type semiconductor layer; and

forming two second electrode pads and second pad extensions on the transparent electrode layer.

14. The method of claim 13, wherein the lower transparent electrode layer is wet-etched using an acid to form the nanoparticles.

15. The method of claim 13, wherein the lower transparent electrode layer is patterned by photolithography and etching to form the nanoparticles.

16. A method of fabricating a light emitting diode (LED), the method comprising:

forming epitaxial layers on a substrate, the epitaxial layers comprising a first conductivity-type semiconductor layer, an active layer, and a second conductivity-type semiconductor layer;

etching the epitaxial layers to expose first regions of the first conductivity-type semiconductor layer;

forming a transparent electrode layer on the epitaxial layers;

patterning the transparent electrode layer to form holes exposing the second conductivity-type semiconductor layer;

forming an insulation layer to cover the transparent electrode layer;

patterning the insulation layer to form micro-lenses arranged in the holes;

forming a first electrode pad and first pad extensions on the first regions of the first conductivity-type semiconductor layer; and

forming two second electrode pads and second pad extensions on the transparent electrode layer.

17. A light emitting diode, comprising:

a substrate;

a light emitting structure arranged on the substrate, the light emitting structure comprising a first conductivity-type semiconductor layer, an active layer, and a second conductivity-type semiconductor layer;

a transparent electrode layer arranged on the second conductivity-type semiconductor layer, the transparent electrode comprising an upper convex-concave surface comprising a plurality of concave portions; and

a plurality of micro-lenses arranged on the transparent electrode layer and covering the transparent electrode layer concave portions.

18. The light emitting diode of claim 17, wherein the transparent electrode layer concave portions comprise blind holes having a depth less than a thickness of the transparent electrode layer.

19. The light emitting diode of claim 17, wherein the transparent electrode layer concave portions comprise through-holes in the transparent electrode layer.

20. The light emitting diode of claim 17, wherein the micro-lenses comprise a material having a lower refractive index than the transparent electrode layer.

21. The light emitting diode of claim 20, wherein the micro-lenses comprise SiO₂.

22. The light emitting diode of claim 20, wherein the second conductivity-type semiconductor layer comprises a GaN-based semiconductor layer, the transparent electrode layer comprises an indium tin oxide (ITO) layer, and the micro-lenses comprise SiO₂.

23. The light emitting diode of claim 17, wherein the micro-lenses comprise a vertical cross-section, a width of which gradually decreases in a direction away from the substrate.

24. The light emitting diode of claim 17, wherein the micro-lenses comprise a vertical cross-section, which comprises at least two inclined surfaces with an obtuse angle defined therebetween.

25. The light emitting diode of claim 17, wherein the micro-lenses comprise a horizontal cross-section of a circular shape, an elliptical shape, a hexagonal shape, a rectangular shape, or a triangular shape.

26. A method of fabricating a light emitting diode (LED), comprising:

forming epitaxial layers on a substrate, the epitaxial layers comprising a first conductivity-type semiconductor layer, an active layer, and a second conductivity-type semiconductor layer;

etching the epitaxial layers to expose first regions of the first conductivity-type semiconductor layer;

forming a transparent electrode layer on the epitaxial layers;

forming a convex-concave surface on the transparent electrode layer, the convex-concave surface comprising a plurality of concave portions; and

forming a plurality of micro-lenses comprising a transparent material, the micro-lenses covering the concave portions.

27. The method of claim 26, wherein transparent electrode layer is partially etched to form blind holes when forming the convex-concave surface.

28. The method of claim 26, wherein the transparent electrode layer is etched to a depth exposing the second conductivity-type semiconductor layer to form through-holes when forming the convex-concave surface.

29. The method of claim 26, wherein forming the plurality of micro-lenses comprises forming a transparent insulation layer covering the transparent electrode layer and etching the transparent insulation layer to form the micro-lenses at positions corresponding to the concave portions of the transparent electrode layer.