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

• US 8,362,459 B2
• Filed: 02/17/2011
• Issued: 01/29/2013
• Est. Priority Date: 02/25/2010
• Status: Active Grant

• Current Assignee: Suzhou Lekin Semiconductor Company Limited
• Original Assignee: LG Innotek Company Limited (LG Corporation)
• Inventors: Kim, Sun Kyung
• Primary Examiner(s): Maldonado, Julio J
• Assistant Examiner(s): SHOOK, DANIEL P
• Application Number:
  US13/029,685
• Publication Number:
  US 20110204324A1
• Time in Patent Office: 712 Days
• Field of Search: 257/13, 257/98, 257/100, 257/E33.068, 257/E33.069, 438/29, 438/32
• US Class Current: 257/13
• CPC Class Codes: F21K 9/00 Light sources using semiconductor devices as light-generating elements, e.g. using light-emitting diodes [LED] or lasers
• CPC Class Codes: G02B 6/0073 Light emitting diode [LED]
• CPC Class Codes: G02B 6/0083 Details of electrical connections of light sources to drivers, circuit boards, or the like
• 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 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 2933/0083 Periodic patterns for optical field-shaping in or on the semiconductor body or semiconductor body package, e.g. photonic bandgap structures
• 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 33/007 comprising nitride compounds
• CPC Class Codes: H01L 33/02 characterised by the semiconductor bodies
• 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 33/42 Transparent materials

Abstract

The light emitting device includes a substrate, a first conductive type semiconductor layer, an active layer, a second conductive type semiconductor layer, and a light-transmitting electrode layer. The second conductive type semiconductor layer has a thickness satisfying Equation: 2·Φ1+Φ2=N·2π±Δ, (0≦Δ≦π/2), where Φ1 is a phase change that is generated when light of a vertical direction passes through the second conductive type semiconductor layer, Φ2 is a phase change that is generated when the light is reflected by the light-transmitting electrode layer, and N is a natural number.

Claims

1. A light emitting device comprising:

a substrate;

a light-emitting structure layer on the substrate, the light-emitting structure layer including a first conductive type semiconductor layer, a second conductive type semiconductor layer, and an active layer between the first and second conductive type semiconductor layers; and

a light-transmitting electrode layer on the second conductive type semiconductor layer,

wherein the second conductive type semiconductor layer has a thickness satisfying Equation (1);

2·

Φ

1+Φ

2=N·

2π

±

Δ

,(0≦

Δ

≦

π

/2) 

 

(1)

where Φ

1 is a phase change that is generated when light of a vertical direction passes through the second conductive type semiconductor layer, Φ

2 is a phase change that is generated when the light is reflected by the light-transmitting electrode layer, and N is a natural number,

wherein Φ

1 is expressed as Equation (2);

Φ

1=2π

n₂d/λ

 

 

(2)

where n₂ is a refractive index of the second conductive type semiconductor layer, λ

is a wavelength of light emitted from the active layer, and d is the thickness of the second conductive type semiconductor layer,

wherein the active layer has a thickness equal to or less than λ

/n₁, where n₁ is a refractive index of the active layer,

wherein all layers between the active layer and the substrate are formed in a nitride-based semiconductor.

2. The light emitting device according to claim 1, wherein the thickness of the second conductive type semiconductor layer ranges from about 90 nm to about 110 nm.

3. The light emitting device according to claim 2, wherein light reflected by the light-transmitting electrode layer and traveling to the substrate and light emitted from the active layer and traveling to the substrate generate the constructive interference by the thickness of the second conductive type semiconductor layer and the active layer.

4. The light emitting device according to claim 1, wherein the light-transmitting electrode layer comprises at least one of ITO, In—

ZnO (IZO), Ga—

ZnO (GZO), Al—

ZnO (AZO), Al—

Ga ZnO (AGZO), indium gallium tin oxide (IGTO), aluminum zinc oxide (AZO), antimony tin oxide (ATO), gallium zinc oxide (GZO), In—

Ga ZnO (IGZO), IrOx, RuOx, RuOx/ITO, Ni/IrOx/Au, and Ni/IrOx/Au/ITO.

5. The light emitting device according to claim 1, wherein the light-transmitting electrode layer comprises a light extraction structure disposed therein.

6. The light emitting device according to claim 5, wherein the light extraction structure has a random roughness shape.

7. The light emitting device according to claim 5, wherein the light extraction structure comprises a photonic crystal structure.

8. The light emitting device according to claim 1, wherein the substrate has a refractive index lower than a refractive index of the first conductive type semiconductor layer.

9. The light emitting device according to claim 1, comprising a first electrode on the first conductive type semiconductor layer, and a second electrode on the light-transmitting electrode layer.

10. The light emitting device according to claim 1, wherein the substrate has an unevenness structure on a top surface and a bottom surface.

11. The light emitting device according to claim 10, wherein the thickness of the second conductive type semiconductor layer ranges from about 90 nm to about 110 nm.

12. A light emitting device comprising:

a light-transmitting substrate;

a light-emitting structure layer on the light-transmitting substrate, the light-emitting structure layer including a first conductive type semiconductor layer, a second conductive type semiconductor layer, and an active layer between the first and second conductive type semiconductor layers; and

a light-transmitting electrode layer on the second conductive type semiconductor layer,

wherein the light-transmitting electrode layer transmits a portion of the incident light, and reflects the other portion of the incident light;

the second conductive type semiconductor layer has a thickness satisfying Equation (1) to allow light reflected by the light-transmitting electrode layer and traveling to the light-transmitting substrate and light emitted from the active layer and traveling to the light-transmitting substrate to generate a constructive interference;

2·

Φ

1+Φ

2=N·

2π

±

Δ

,(0≦

Δ

≦

π

/2) 

 

(1)

where Φ

1 is a phase change that is generated when light of a vertical direction passes through the second conductive type semiconductor layer, Φ

₂ is a phase change that is generated when the light is reflected by the light-transmitting electrode layer, and N is a natural number;

the active layer has a thickness equal to or less than λ

/n₁, where n₁ is a refractive index of the active layer, and λ

is a wavelength of light emitted from the active layer; and

the light-transmitting substrate has a refractive index lower than a refractive index of the first conductive type semiconductor layer,

wherein Φ

2 equals 0,

wherein Φ

1 is expressed as Equation (2);

Φ

1=2π

n₂d/λ

 

 

(2)

where n₂ is a refractive index of the second conductive type semiconductor layer, λ

is the wavelength of the light emitted from the active layer, and d is the thickness of the second conductive type semiconductor layer,

wherein the active layer has a thickness equal to or less than λ

/n₁, where n₁ is a refractive index of the active layer,

wherein all layers between the active layer and the light-transmitting substrate are formed in a nitride based semiconductor.

13. The light emitting device according to claim 12, wherein the first conductive type semiconductor layer is an n-type semiconductor layer having a chemical formula of In_xAl_yGa_1-x-yN (0≦

x≦

1, 0≦

y≦

1, 0≦

x+y≦

1), and the second conductive type semiconductor layer is a p-type semiconductor layer having a chemical formula of In_xAl_yGa_1-x-yN (0≦

x≦

1, 0≦

y≦

1, 0≦

x+y≦

1).

14. The light emitting device according to claim 12, wherein the light-transmitting substrate comprises a sapphire (Al₂O₃) substrate.

15. The light emitting device according to claim 12, wherein the light-transmitting substrate has an unevenness structure on at least one of a top surface and a bottom surface.

16. The light emitting device according to claim 15, comprising a reflection layer on the bottom surface of the light-transmitting substrate.

17. The light emitting device according to claim 15, comprising a first semiconductor layer of the all layers between the light-transmitting substrate and the first conductive type semiconductor layer, wherein the first semiconductor layer has a lattice constant value between a lattice constant value of the light-transmitting substrate and a lattice constant value of the first conductive type semiconductor layer.

18. The light emitting device according to claim 15, comprising a first semiconductor layer of the all layers between the light-transmitting substrate and the first conductive type semiconductor layer, the first semiconductor layer having a conductivity lower than a conductivity of the first conductive type semiconductor layer.

19. A light emitting device package comprising:

a body;

first and second lead electrodes on the body;

a light emitting device on at least one of the first and second lead electrodes; and

a molding member on the light emitting device,

wherein the light emitting device comprises;

a substrate;

a light-emitting structure layer on the substrate, the light-emitting structure layer including a first conductive type semiconductor layer, a second conductive type semiconductor layer, and an active layer between the first and second conductive type semiconductor layers; and

a light-transmitting electrode layer on the second conductive type semiconductor layer, and the second conductive type semiconductor layer has a thickness satisfying Equation (1);

2·

Φ

1+Φ

2=N·

2π

±

Δ

,(0≦

Δ

≦

π

/2) 

 

(1)

where Φ

1 is a phase change that is generated when light of a vertical direction passes through the second conductive type semiconductor layer, Φ

2 is a phase change that is generated when the light is reflected by the light-transmitting electrode layer, and N is a natural number,

wherein Φ

1 is expressed as Equation (2);

Φ

1=2π

n₂d/λ

 

 

(2)

where n₂ is a refractive index of the second conductive type semiconductor layer, λ

is a wavelength of light emitted from the active layer, and d is the thickness of the second conductive type semiconductor layer,

wherein Φ

2 equals 0,

wherein the active layer has a thickness equal to or less than λ

/n₁, where n₁ is a refractive index of the active layer,

wherein all layers between the active layer and the light-transmitting substrate are formed in a nitride-based semiconductor.