Light-emitting element

• US 20030122478A1
• Filed: 05/29/2002
• Published: 07/03/2003
• Est. Priority Date: 05/29/2001
• Status: Active Grant

• Current Assignee: Toyoda Gosei Company Limited (Toyota Motor Corporation)
• Original Assignee: Toyoda Gosei Company Limited (Toyota Motor Corporation)
• Inventors: Koike, Masayoshi, Kato, Hideaki, Suehiro, Yoshinobu
• Granted Patent: US 6,946,788 B2
• Time in Patent Office: Days
• US Class Current: 313/498
• CPC Class Codes: H01L 33/08 with a plurality of light emitting regions, e.g. laterally discontinuous light emitting layer or photoluminescent region integrated within the semiconductor body H01L27/15 takes precedence
• 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 33/24 of the light emitting region, e.g. non-planar junction
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/38 with a particular shape

Abstract

A light-emitting element has a light-emitting layer and at lease one light-extracting portion. At least a partial part of the light-extracting portion is formed into a concave or convex surface for enhancing the efficiency of extracting light. Another light-emitting element has a light-emitting layer and a concave or convex surface for reflecting light emitted from the light-emitting layer toward one or more other surfaces of the light-emitting element through an inside of the light-emitting element.

Claims

1. A light-emitting element comprising:

a light-emitting layer; and

at lease one light-extracting portion,

wherein at least a partial part of the light-extracting portion is formed into a concave or convex surface for enhancing the efficiency of extracting light.

2. A light-emitting element according to claim 1, wherein said concave or convex surface of said light-extracting portion is shaped to be substantially convex, and

substantially equal refractivity is kept between said light-emitting layer and said light-extracting portion.

3. A light-emitting element according to claim 1, wherein said light-emitting element is mounted so that said light-emitting layer is located on a bottom surface side of said light-emitting element.

4. A light-emitting element according to claim 3, wherein electrodes opposite in polarity are formed on said bottom surface side.

5. A light-emitting element according to claim 2, wherein said substantially convex light-extracting portion is constituted by at least 5 light-extracting surfaces, and said light-emitting layer exists in a direction substantially perpendicular to each of said light-extracting surfaces.

6. A light-emitting element according to claim 2, wherein said substantially convex light-extracting portion includes a curved light-extracting surface, and said light-emitting layer exists in a direction substantially perpendicular to said light-extracting surface.

7. A light-emitting element according to claim 2, wherein said light-emitting layer is a part of a crystal layer and located in a vicinity of a central portion of said substantially convex light-extracting portion.

8. A light-emitting element according to claim 2, wherein said light-emitting element comprises a plurality of said substantially convex light-extracting portions.

9. A light-emitting element according to claim 8, wherein said plurality of substantially convex light-extracting portions are arranged in a lattice structure.

10. A light-emitting element according to claim 7, wherein said light-emitting layer is formed only in a portion of said crystal layer of said light-emitting element, said portion of said crystal layer being substantially perpendicular to said at least one light-extracting portion.

11. A light-emitting element according to claim 1, wherein said light-extracting portion is constituted by surfaces including a curved surface.

12. A light-emitting element according to claim 11, wherein said curved surface includes a cylindrical surface.

13. A light-emitting element according to claim 1, wherein at least a circumference of a side surface of said light-emitting layer is wholly or partially formed into a concavo-convex side surface as said concave or convex surface having a concavo-convex shape.

14. A light-emitting element according to claim 13, wherein concavities and convexities of said concavo-convex side surface are of a curve with a change in curvature.

15. A light-emitting element according to claim 13, wherein said concavo-convex side surface has a taper angle with respect to said light-emitting layer.

16. A light-emitting element according to claim 13, wherein said concavo-convex side surface is formed in an etching step.

17. A light-emitting element according to claim 13, wherein said concavo-convex side surface is formed in a step of patterning said light-emitting layer.

18. A light-emitting element according to claim 13, wherein said concavo-convex side surface is formed in a step of separating said light-emitting element.

19. A light-emitting element according to claim 13, wherein said light-emitting element is formed on a substrate whose refractive index is smaller than a refractive index of said light-emitting layer.

20. A light-emitting element according to claim 19, wherein each layer of said light-emitting element formed on said substrate is made of a Group III nitride compound semiconductor.

21. A light-emitting element according to claim 13, wherein a top surface of said light-emitting element is also formed into a concavo-convex shape.

22. A light-emitting element comprising:

a light-emitting layer; and

a concave or convex surface for reflecting light emitted from said light-emitting layer toward one or more other surfaces of said light-emitting element through an inside of said light-emitting element.

23. A light-emitting element according to claim 22, wherein selected ones of reflecting grooves and reflecting holes as said concave or convex surface are formed in a bottom surface of said light-emitting element, wherein light emitted from said light-emitting layer is reflected upward by said selected ones of said reflecting grooves and said reflecting holes.

24. A light-emitting element according to claim 23, wherein said light-emitting layer is formed on said bottom surface side.

25. A light-emitting element according to claim 23, wherein electrodes opposite in polarity are formed on said bottom surface side.

26. A light-emitting element according to claim 23, wherein maximum heights of said selected ones of said reflecting grooves and said reflecting holes reach in an internal portion of said light-emitting layer.

27. A light-emitting element according to claim 23, wherein a light-emitting area of said light-emitting layer is formed as split light-emitting areas formed in places other than places where said selected ones of said reflecting grooves and said reflecting holes are formed.

28. A light-emitting element according to claim 23, wherein a substrate lower in refractive index than said light-emitting layer is located above said light-emitting layer.