Light-emitting device

• US 8,049,233 B2
• Filed: 03/09/2007
• Issued: 11/01/2011
• Est. Priority Date: 03/10/2006
• Status: Active Grant

• Current Assignee: Panasonic Semiconductor Solutions Co., Ltd. (Winbond Electronics Corporation)
• Original Assignee: Panasonic Electric Works Company Limited (Panasonic Holdings Corporation)
• Inventors: Fukshima, Hiroshi, Yamae, Kazuyuki, Yasuda, Masaharu
• Primary Examiner(s): Pham; Thanh V
• Assistant Examiner(s): Ligai; Maria
• Application Number:
  US11/813,370
• Publication Number:
  US 20090267092A1
• Time in Patent Office: 1,698 Days
• Field of Search: 257/98, 257/E33.074, 257/E33.065, 257/E33.072, 257E33067-E33069, 438/69, 438/72, 438/29, 438/22, 438/42
• US Class Current: 257/98
• 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 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 33/405 Reflective materials
• CPC Class Codes: H10K 50/854 comprising scattering means
• CPC Class Codes: H10K 50/858 comprising refractive means, e.g. lenses

Abstract

A light-emitting device of the present invention includes: a semiconductor layer 1 including a light-emitting layer 12; a recess/projection portion 14 including recesses and projections formed in a pitch larger than a wavelength of light emitted from the light-emitting layer 12, the recess/projection portion 14 being formed in a whole area or a partial area of the surface of the semiconductor layer which light is emitted from; and a reflective layer formed on an opposite surface of the semiconductor layer to the surface from which light is emitted, the reflective layer having a reflectance of 90% or more. According to the light-emitting device having such arrangement, the light can be emitted efficiently by synergetic effect of the reflective layer and the recess/projection portion.

Claims

1. A light-emitting device comprising:

a semiconductor layer comprising

a light-emitting layer;

a recess/projection portion including recesses and projections formed in a pitch larger than a wavelength of light emitted from the light-emitting layer, the recess/projection portion being formed in a whole area or a partial area of the surface of the semiconductor layer which light is emitted from; and

a reflective layer formed on an opposite surface of the semiconductor layer to the surface from which light is emitted, the reflective layer having a reflectance of 90% or more,

wherein the semiconductor layer includes a GaN system material, and the reflective layer includes an alloy containing silver as a primary element, wherein the reflective layer is in ohmic contact with the semiconductor.

2. The light-emitting device according to claim 1, wherein the recesses and projections of the recess/projection portion are formed periodically or randomly.

3. The light-emitting device according to claim 1, wherein the recess/projection portion has a shape acting as a lens.

4. The light-emitting device according to claim 3, wherein the shape acting as a lens is a shape of Fresnel lens.

5. The light-emitting device according to claim 1, wherein the reflective layer includes:

a conductive oxide layer formed above a surface of the semiconductor layer;

a metal layer formed on the conductive oxide layer, the metal layer consisting of silver, aluminum, a silver alloy containing silver as a primary element, or an aluminum alloy containing aluminum as a primarily element; and

a platinum layer formed between the semiconductor layer and the conductive oxide layer, the platinum layer having a mesh-like shape or an island-like shape.

6. The light-emitting device according to claim 1, wherein the reflective layer includes a DBR.

7. The light-emitting device according to claim 1, wherein the reflective layer includes:

a metal layer consisting of aluminum, silver, or a silver alloy containing silver as a primary element; and

a DBR formed on the metal layer.

8. The light-emitting device according to claim 7, wherein each of the layers constituting the DBR has such a thickness as to allow light rays emitted from the light-emitting layer and having a high intensity range and coming at an angular range of a low transmissivity to reflect on the reflective layer at an increased reflectance.

9. The light-emitting device according to claim 1, wherein the reflective layer includes:

a conductive oxide layer formed above a surface of the semiconductor layer;

a DBR layered on the conductive oxide layer;

a metal layer formed on the DBR layer and consisting of silver, aluminum, a silver alloy containing silver as a primary element, or an aluminum alloy containing aluminum as a primary element; and

a platinum layer formed between the semiconductor layer and the conductive oxide layer, and having a mesh-like shape or an island-like shape.

10. The light-emitting device according to claim 9, wherein the DBR has a mesh-like shape or an island-like shape.

11. The light-emitting device according to claim 1, wherein the reflective layer includes a photonic crystal.

12. The light-emitting device according to claim 1, wherein a distance between a bottom plane of the recess/projection portion and an opposite surface of the semiconductor layer to the recess/projection portion is within several folds longer than a wavelength of light emitted from the light-emitting layer and traveling in the semiconductor layer.

13. The light-emitting device according to claim 1, wherein the reflective layer serves as a p-type electrode, further comprising an n-type electrode formed on a surface of the semiconductor layer and having a reflectance of 80% or more, and being operable to associate with the p-type electrode.

14. The light-emitting device according to claim 13, wherein the n-type electrode includes:

a conductive oxide layer formed on the surface of the semiconductor layer;

a metal layer formed on the conductive oxide layer and consisting of silver, aluminum, a silver alloy containing silver as a primary element, or an aluminum alloy containing aluminum as a primary element; and

a platinum layer formed between the semiconductor layer and the conductive oxide layer, the platinum layer having a mesh-like shape or an island-like shape.

15. The light-emitting device according to claim 13, wherein the n-type electrode includes:

a conductive oxide layer formed on the surface of the semiconductor layer;

a DBR formed on the conductive oxide layer;

a metal layer formed on the DBR and consisting of silver, aluminum, a silver alloy containing silver as a primary element, or an aluminum alloy containing aluminum as a primary element; and

a platinum layer formed between the semiconductor layer and the conductive oxide layer, the platinum layer having a mesh-like shape or an island-like shape.

16. The light-emitting device according to claim 15, wherein the DBR has a mesh-like shape or an island-like shape.

17. The light-emitting device according to claim 1, further comprising a wavelength converting layer formed on a light-extraction surface of the semiconductor layer and adapted for converting the wavelength of light rays emitted from the semiconductor layer and irradiating the same.

18. The light-emitting device according to claim 1, wherein said device has a light extraction efficiency of 55% or more.

19. A method for producing a light-emitting device, comprising:

a semiconductor layer comprising

a light-emitting layer, and

a recess/projection portion including recesses and projections formed in a pitch larger than a wavelength of light emitted from the light-emitting layer, the recess/projection portion being formed on a whole area or a partial area of the surface of the semiconductor layer from which light is emitted;

a wavelength converting layer formed on a light-extraction surface of the semiconductor layer and adapted for converting the wavelength of light rays emitted from the semiconductor layer and irradiating the same; and

a reflective layer formed on an opposite surface of the semiconductor layer to the surface from which light is emitted, the reflective layer having a reflectance of 90% or more, the method comprising;

depositing a material having a refractive index which is substantially the same as that of the semiconductor layer to form the recess/projection portion, and

forming a wavelength converting layer on a light-extraction surface of the semiconductor layer wherein the reflective layer is in ohmic contact with the semiconductor.

20. A light-emitting device comprising:

a semiconductor layer comprising

a light-emitting layer, and

a recess/projection portion including recesses and projections formed in a pitch larger than a wavelength of light emitted from the light-emitting layer, the recess/projection portion being formed in a whole area or a partial area of the surface of the semiconductor layer which light is emitted from; and

a reflective layer formed on an opposite surface of the semiconductor layer to the surface from which light is emitted, the reflective layer having a reflectance of 95% or more, wherein the semiconductor layer includes a GaN system material, and said reflective layer includes;

a conductive oxide layer formed on a surface of the semiconductor layer;

a metal layer formed on the conductive oxide layer, the metal layer comprising an alloy containing silver as a primary element; and

a platinum layer formed between the semiconductor layer and the conductive oxide layer, the platinum layer having a mesh-like shape or an island-like shape wherein the reflective layer is in ohmic contact with the semiconductor.

21. The light-emitting device according to claim 20, wherein said device has a light extraction efficiency of 77% or more.