Light emitting diode having distributed Bragg reflector

• US 8,963,183 B2
• Filed: 02/06/2013
• Issued: 02/24/2015
• Est. Priority Date: 07/28/2010
• Status: Active Grant

• Current Assignee: Seoul Viosys Co., Ltd. (Seoul Semiconductor Co., Ltd.)
• Original Assignee: Seoul Viosys Co., Ltd. (Seoul Semiconductor Co., Ltd.)
• Inventors: Suh, Duk Il, Kim, Jae Moo, Kim, Kyoung Wan, Yoon, Yeo Jin, Kim, Ye Seul, Oh, Sang-Hyun, Lee, Jin Woong
• Primary Examiner(s): Moore, Whitney T
• Assistant Examiner(s): GALVIN III, JOSEPH M
• Application Number:
  US13/760,637
• Publication Number:
  US 20130146925A1
• Time in Patent Office: 748 Days
• Field of Search: 257/79, 257/89, 257/98, 257/E33.064, 257/E33.068
• US Class Current: 257/98
• 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 2224/73265 Layer and wire connectors
• 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 33/10 with a light reflecting structure, e.g. semiconductor Bragg reflector
• CPC Class Codes: H01L 33/38 with a particular shape
• CPC Class Codes: H01L 33/42 Transparent materials
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector
• CPC Class Codes: H01L 33/50 Wavelength conversion elements

Abstract

A light-emitting diode (LED) according to an exemplary embodiment includes a light-emitting structure arranged on a first surface of a substrate, the light-emitting structure including a first conductivity-type semiconductor layer, a second conductivity-type semiconductor layer, and an active layer interposed between the first conductivity-type semiconductor layer and the second conductivity-type semiconductor layer. A first distributed Bragg reflector is arranged on a second surface of the substrate opposite to the first surface, the first distributed Bragg reflector to reflect light emitted from the light-emitting structure. The first distributed Bragg reflector has a reflectivity of at least 90% with respect to blue, green, and red light.

Claims

1. A light-emitting diode (LED), comprising:

a substrate having a first surface and an opposing second surface;

a light-emitting structure disposed on the first surface of the substrate, the light-emitting structure comprising;

a first conductivity-type semiconductor layer;

a second conductivity-type semiconductor layer; and

an active layer interposed between the first conductivity-type semiconductor layer and the second conductivity-type semiconductor layer;

refractive index-grading layers covering at least a portion of the second conductivity-type semiconductor layer, the refractive index-grading layers having different refractive indices from each other; and

a distributed Bragg reflector disposed on the second surface of the substrate, wherein the distributed Bragg reflector has a reflectivity of at least 90% with respect to blue light, green light, and red light,

wherein the refractive index-grading layers comprise a first grading layer that is configured as a current spreading layer and directly contacts the light-emitting structure, and a second grading layer that is configured as an insulation layer, and

wherein both of the first grading layer and the second grading layer have a refractive index that decreases in a direction away from the light-emitting structure.

2. The LED of claim 1, wherein the refractive index-grading layers are transparent to light generated in the light-emitting structure.

3. The LED of claim 1, wherein:

the first grading layer comprises ITO or ZnO; and

the second grading layer comprises SiO₂.

4. The LED of claim 1, further comprising a second electrode pad disposed on the current spreading layer.

5. The LED of claim 4, wherein the second electrode pad is electrically connected to the second conductivity-type semiconductor layer directly or through the current spreading layer.

6. The LED of claim 1, wherein at least one of the refractive index-grading layers has a refractive index or a density that decreases in a gradual or stepwise manner, in a direction away from the light-emitting structure.

7. The LED of claim 1, wherein:

the second conductivity-type semiconductor layer has a mesa structure; and

the second grading layer covers a sidewall of the mesa structure and an exposed surface of the first conductivity-type semiconductor layer.

8. The LED of claim 1, wherein the distributed Bragg reflector has a laminate structure comprising SiO₂layers and at least one TiO₂layer.

9. The LED of claim 1, wherein outermost layers of the distributed Bragg reflector are SiO₂layers.

10. A light-emitting diode (LED), comprising:

a substrate having a first surface and an opposing second surface;

a light-emitting structure disposed on the first surface of the substrate, the light-emitting structure comprising;

a first conductivity-type semiconductor layer;

a second conductivity-type semiconductor layer; and

an active layer interposed between the first conductivity-type semiconductor layer and the second conductivity-type semiconductor layer;

a first refractive index-grading layer disposed directly on at least a portion of the second conductivity-type semiconductor layer, comprising a transparent conductive oxide, and having a refractive index or a density that decreases in a gradual or stepwise manner, in a direction away from the light-emitting structure; and

a second refractive index-grading layer covering the first refractive index-grading layer, the second refractive index-grading layer having a different refractive index from the first refractive index-grading layer.

11. The LED of claim 10, further comprising:

a distributed Bragg reflector disposed on the second surface of the substrate,

wherein the distributed Bragg reflector has a reflectivity of at least 90% with respect to blue, green, and red light.

12. The LED of claim 10, wherein:

the first grading layer comprises ITO or ZnO; and

the second grading layer comprises SiO₂.

13. The LED of claim 10, wherein the second grading layer comprises laminated SiO₂ layers, the refractive index or density of the SiO₂ layers decreasing in a gradual or stepwise manner, in a direction away from the light-emitting structure.

14. The LED of claim 10, wherein:

the second conductivity-type semiconductor layer has a mesa structure; and

the second refractive index-grading layer covers a mesa sidewall and an exposed surface of the second conductivity-type semiconductor layer.