Light emitting device, light emitting device package, and lighting system

• US 8,431,945 B2
• Filed: 04/22/2011
• Issued: 04/30/2013
• Est. Priority Date: 04/23/2010
• Status: Active Grant

• Current Assignee: Suzhou Lekin Semiconductor Company Limited
• Original Assignee: LG Innotek Company Limited (LG Corporation)
• Inventors: Choi, Hyun Min, Kim, Sun Kyung, Choi, Woon Kyung
• Primary Examiner(s): Such, Matthew W
• Assistant Examiner(s): JOY, JEREMY J
• Application Number:
  US13/092,275
• Publication Number:
  US 20110260188A1
• Time in Patent Office: 739 Days
• Field of Search: 257/98, 257E33068-E33069, 438/29
• US Class Current: 257/98
• CPC Class Codes: H01L 2224/48091 Arched
• 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 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/382 the electrode extending partially in or entirely through the semiconductor body
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector

Abstract

Disclosed are a light emitting device, a light emitting device package, and a lighting system. The light emitting device includes a light emitting structure including a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer on, a light transmissive substrate having a refractive index lower than a refractive index of a compound semiconductor layer, and a mirror structure layer having a structure in which a first mirror layer having a first refractive index and a second mirror layer having a second refractive index different from the first refractive index are alternately stacked on each other. The first mirror layer has a thickness of W·λ/(4·n1·m), and the second mirror layer has a thickness of W·λ/(4·n2·m) in which the W represents a weight constant in a range of about 1.05 to about 1.25.

Claims

1. A light emitting device comprising:

a light emitting structure that includes a first conductive semiconductor layer, an active layer on the first conductive semiconductor layer, and a second conductive semiconductor layer on the active layer;

a light transmissive substrate disposed under the light emitting structure and having a refractive index that is less than a refractive index of the first conductive semiconductor layer;

a mirror structure layer disposed under the light transmissive substrate and including a first mirror layer having a first refractive index and a second mirror layer having a second refractive index different from the first refractive index, wherein the first mirror layer and the second mirror layer are alternately stacked on each other; and

a first electrode layer under the mirror structure layer,

wherein the first mirror layer has a thickness of W·

λ

/(4·

n1·

m), and the second mirror layer has a thickness of W·

λ

/(4·

n2·

m) in which λ

represents a wavelength of a light emitted from the light emitting structure, n1 represents the first refractive index, n2 represents the second refractive index, m represents a natural number, and W represents a weight constant in a range of about 1.05 to about 1.25.

2. The light emitting device of claim 1, wherein the first mirror layer includes one selected from the group consisting of SiO₂, TiO₂, MgF, and SiN_x and the second mirror layer includes another one selected from the group consisting of SiO₂, TiO₂, MgF, and SiN_x.

3. The light emitting device of claim 1, wherein the weight constant has a value in a range of about 1.1 to about 1.2.

4. The light emitting device of claim 1, wherein the mirror structure layer includes a pair of the first and second mirror layers repeatedly stacked on each other at least four times.

5. The light emitting device of claim 1, wherein the substrate includes one selected from the group consisting of sapphire (Al₂O₃), GaN, ZnO, and AlN.

6. The light emitting device of claim 1, wherein at least one layer of the light emitting structure includes a compound semiconductor material having a compositional formula of In_xAl_yGa_1-x-yN (0≦

x≦

1, 0≦

y≦

1 and 0≦

x+y≦

1).

7. The light emitting device of claim 1, further comprising:

a current spreading layer on the second conductive semiconductor layer; and

a second electrode on the current spreading layer,

wherein a portion of the first electrode layer is connected to the first conductive semiconductor layer.

8. The light emitting device of claim 1, further comprising at least one of a first light extraction structure on a top surface of the substrate and a second light extraction structure on a lower surface of the substrate.

9. The light emitting device of claim 1, wherein a difference between the first and second refractive indexes in the mirror structure layer is 1 or more.

20. The light emitting device of claim 7, wherein the first electrode layer covers at least 80% of an area of a lower surface of the mirror structure layer.

10. A light emitting device comprising:

a light emitting structure that includes a first conductive semiconductor layer, an active layer on the first conductive semiconductor layer, and a second conductive semiconductor layer on the active layer;

a substrate disposed under the light emitting structure and having a refractive index that is less than a refractive index of the first conductive semiconductor layer;

a mirror structure layer disposed under the substrate and including a plurality of first mirror layers having a first refractive index that is greater than a refractive index of the substrate, and a plurality of second mirror layers disposed between the first mirror layers and having a second refractive index that is less than the first refractive index;

a first electrode layer under the mirror structure layer; and

a second electrode on the light emitting structure,

wherein the first mirror layer has a thickness of W·

λ

/(4·

n1·

m), and the second mirror layer has a thickness of W·

λ

/(4·

n2·

m) in which λ

represents a wavelength of a light emitted from the light emitting structure, n1 represents the first refractive index, n2 represents the second refractive index, m represents a natural number, and W represents a weight constant in a range of about 1.05 to about 1.25.

11. The light emitting device of claim 10, wherein a lower surface of the mirror structure layer is formed of a flat surface, and a top surface of the mirror structure layer is formed of an uneven surface.

12. The light emitting device of claim 10, wherein a pair of the first and second mirror layers include at least one of a TiO₂/SiO₂ stack structure, a TiO₂/MgF stack structure, and a TiO₂/SiOx stack structure.

13. The light emitting device of claim 10, wherein the second mirror layers include at least four layers, and one of the four layers contact a lower surface of the substrate.

14. The light emitting device of claim 11, wherein the substrate is disposed on a lower surface thereof with a concavo-convex light extraction structure, and at least one layer of the mirror structure layer includes a concavo-convex layer.

15. The light emitting device of claim 10, wherein a portion of the first electrode layer contacts an inner part of the first conductive semiconductor layer.

16. The light emitting device of claim 10, wherein the first electrode layer covers at least 80% of an area of a lower surface of the mirror structure layer.

17. The light emitting device of claim 10, wherein a difference in thicknesses between the first mirror layer and the second mirror layer is in a range of about 50 nm to about 70 nm.

18. The light emitting device of claim 17, wherein a difference between the first and second refractive indexes of the mirror structure layer is 1 or more.

19. A light emitting device package comprising:

a body;

a plurality of lead electrodes on the body;

a light emitting device electrically connected to the lead electrodes; and

a molding member covering the light emitting device,

wherein the light emitting device comprises;

a light emitting structure that includes a first conductive semiconductor layer, an active layer on the first conductive semiconductor layer, and a second conductive semiconductor layer on the active layer;

a light transmissive substrate disposed under the light emitting structure and having a refractive index that is less than a refractive index of a compound semiconductor layer; and

a mirror structure layer disposed under the light transmissive substrate and including a first mirror layer having a first refractive index and a second mirror layer having a second refractive index different from the first refractive index, wherein the first mirror layer and the second mirror layer are alternately stacked on each other;

a first electrode layer under the mirror structure layer; and

a second electrode on the light emitting structure,

wherein the first mirror layer has a thickness of W·

λ

/(4·

n1·

m), and the second mirror layer has a thickness of W·

λ

/(4·

n2·

m) in which λ

represents a wavelength of a light emitted from the light emitting structure, n1 represents the first refractive index, n2 represents the second refractive index, m represents a natural number, and W represents a weight constant in a range of about 1.05 to about 1.25.