Light emitting device and light emitting element having predetermined optical form

• US 7,453,092 B2
• Filed: 08/30/2005
• Issued: 11/18/2008
• Est. Priority Date: 08/31/2004
• Status: Active Grant

• Current Assignee: Toyoda Gosei Company Limited (Toyota Motor Corporation)
• Original Assignee: Toyoda Gosei Company Limited (Toyota Motor Corporation)
• Inventors: Tasumi, Koji, Suehiro, Yoshinobu
• Primary Examiner(s): Louiw; Wai-Sing
• Assistant Examiner(s): ARMAND, MARC ANTHONY
• Application Number:
  US11/214,018
• Publication Number:
  US 20060043402A1
• Time in Patent Office: 1,176 Days
• Field of Search: 257/13, 257/79, 257/80, 257/82, 257/93, 257/99, 257/103, 257/777
• US Class Current: 257/79
• CPC Class Codes: H01L 2224/0401 Bonding areas specifically adapted for bump connectors, e.g. under bump metallisation [UBM]
• CPC Class Codes: H01L 2224/16225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2924/00011 Not 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 33/0093 Wafer bonding; Removal of the growth substrate
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/486 adapted for surface mounting
• CPC Class Codes: H01L 33/56 Materials, e.g. epoxy or silicone resin

Abstract

A light emitting device having: a predetermined optical form that is provided on a surface of an LED element mounted on a base, the predetermined optical form being made to allow an increase in efficiency of taken out light from an inside of the LED element; and a sealing material that seals the predetermined optical form. The sealing material has a refractive index of 1.6 or more, the predetermined optical form is formed in a surface of a substrate of the LED element, and the substrate has a refractive index nearly equal to that of a light emitting layer of the LED element.

Claims

1. A light emitting device, comprising:

a predetermined optical form that is provided on a surface of an LED element mounted on a base, the predetermined optical form being made to allow an increase in efficiency of taken out light from an inside of the LED element; and

a sealing material that seals the LED element, wherein

the sealing material has a refractive index of 1.6 or more,

the predetermined optical form is formed to comprise a combination of uneven forms having different forms and different depths in a semiconductive surface of a substrate of the LED element,

the substrate has a refractive index nearly equal to that of a light emitting layer of the LED element,

the LED element is flip mounted on the base,

the sealing material comprises an SiO₂—

Nb₂O₅ based glass as a matrix material, and

the sealing material directly contacts the predetermined optical form.

2. The light emitting device according to claim 1, wherein:

the predetermined optical form comprises a light transmitting material layer having a refractive index that is no less than the average of that of the light emitting layer and the sealing material of the LED element.

3. The light emitting device according to claim 1, wherein:

the predetermined optical form is formed in a light transmitting material layer which is provided to a semiconductor layer that is exposed by peeling the substrate of the LED element, and has the same refractive index as that of the light emitting layer of the LED element.

4. ) The light emitting device according to claim 1, wherein:

the predetermined optical form comprises an uneven surface having a portion in step form of which the angle of inclination is no greater than sin<sup>−

1</sup> (n2/n1) (where n1 is the refractive index of the light emitting layer of the LED element, and n2 is the index refraction of the sealing material) relative to the direction of the normal of the light emitting layer.

5. The light emitting device according to claim 1, wherein:

a number of conical surfaces are formed in the predetermined optical form.

6. The light emitting device according to claim 1, wherein:

the outer form of the sealing material is formed in an optical surface form where light that is emitted from the LED element enters at an angle that is different from the critical angle, defined by the ratio of the indices of refraction relative to the sealing material.

7. The light emitting device according to claim 1, wherein:

the sealing material comprises a light transmitting material of which the refractive index satisfies

n1·

sin45°

<

n2

(where n1 is the refractive index of the light emitting layer of the LED element, and n2 is the refractive index of the sealing material).

8. The light emitting device according to claim 1, wherein:

the base comprises an inorganic material substrate having the same thermal expansion coefficient as the sealing material, where a conductive pattern for supplying power to the light emitting element is formed.

9. The light emitting device according to claim 1, wherein:

the LED element comprises a GaN based semiconductor.

10. The light emitting element according to claim 1, further comprising:

a p-electrode formed of ITO (indium tin oxide).

11. The light emitting device according to claim 2, wherein:

in the predetermined optical form, the light transmitting material layer is formed so as to have a thickness t, in such a manner that

t>

W/(2tan (sin<sup>−

1</sup>(n1/n2)))

where W is the width of the element.

12. The light emitting device according to claim 2, wherein:

the light transmitting material layer has a cut portion where a corner has been cut so as to provide an inclined surface.

13. The light emitting device according to claim 2, wherein:

the refractive index of the sealing material ranges from 0.68 to 0.85 relative to the refractive index of the light emitting layer.

14. The light emitting device according to claim 4, wherein:

the predetermined optical form comprises an uneven surface having an approximately perpendicular step form.

15. The light emitting device according to claim 4, wherein:

the uneven surface comprises a form where a trench is formed around an uneven portion.

16. The light emitting device according to claim 4, wherein:

the portion in step form has a form where sides which are adjacent to each other make contact with each other at different angles.

17. The light emitting device according to claim 16, wherein:

the portion in step form is formed in diamond form.

18. The light emitting device according to claim 8, wherein:

the conductive pattern has a pattern on the side on which the light emitting element is mounted, a pattern on the rear side thereof, and a pattern for electrically connecting the two sides.

19. The light emitting device according to claim 9, wherein:

the sealing material has a refractive index of no less than 1.7.

20. A light emitting device, comprising:

a predetermined optical form that is provided on a surface of an LED element mounted on a base, the predetermined optical form being made to allow an increase in efficiency of taken out light from an inside of the LED element; and

a sealing material that seals the LED element,

wherein the sealing material has a refractive index of 1.6 or more,

the predetermined optical form is formed to comprise a combination of uneven forms having different forms and different depths in a surface of a semiconductor layer that is exposed by peeling a substrate and comprises a surface of the LED element,

the LED element is flip mounted on the base,

the sealing material comprises glass an SiO₂—

Nb₂O₅ based glass as a matrix material, and

the sealing material directly contacts the predetermined optical form.

21. The light emitting device according to claim 20, wherein:

the predetermined optical form comprises a light transmitting material layer having a refractive index that is no less than the average of that of the light emitting layer and the sealing material of the LED element.

22. The light emitting device according to claim 20, wherein:

the predetermined optical form comprises an uneven surface having a portion in step form of which the angle of inclination is no greater than sin<sup>−

1</sup> (n2/n1) (where n1 is the refractive index of the light emitting layer of the LED element, and n2 is the index refraction of the sealing material) relative to the direction of the normal of the light emitting layer.

23. The light emitting device according to claim 20, wherein:

the outer form of the sealing material is formed in an optical surface form where light that is emitted from the LED element enters at an angle that is different from the critical angle, defined by the ratio of the indices of refraction relative to the sealing material.

24. The light emitting device according to claim 20, wherein:

the sealing material comprises a light transmitting material of which the refractive index satisfies

n1·

sin45°

<

n2

(where n1 is the refractive index of the light emitting layer of the LED element, and n2 is the refractive index of the sealing material).

25. The light emitting device according to claim 20, wherein:

the LED element comprises a GaN based semiconductor.

26. The light emitting element according to claim 20, further comprising:

a p-electrode formed of ITO (indium tin oxide).

27. A light emitting element, comprising:

a semiconductor layer that comprises a light emitting layer, a predetermined optical form that is provided on one surface of the semiconductor layer, the predetermined optical form being made to allow an increase in efficiency of taken out light from an inside of the light emitting element (LED element);

an electrode part that is provided on the other surface of semiconductor layer; and

a sealing material that seals the LED element, the sealing material comprising an SiO₂—

Nb₂O₅ based glass as a matrix material,

wherein the predetermined optical form is an uneven surface comprising a rectangular projection of different forms and different depths in a vertical cross section of the semiconductor layer.

28. The light emitting element according to claim 27, wherein:

the predetermined optical form is formed in a surface of a substrate of the LED element, and

the substrate has a refractive index nearly equal to that of the light emitting layer of the LED element.

29. The light emitting element according to claim 27, wherein:

the predetermined optical form is formed in a surface of a semiconductor layer that is exposed by peeling a substrate of the LED element.

30. The light emitting element according to claim 27, wherein:

the rectangular projection comprises sides which are adjacent to each other at different angles in said one surface of the semiconductor layer.

31. The light emitting element according to claim 27, wherein:

the LED element comprises a GaN based semiconductor.

32. The light emitting element according to claim 27, wherein:

the electrode part comprises a p-electrode formed of ITO (indium tin oxide).

33. The light emitting element according to claim 29, wherein:

the rectangular projection comprises a diamond form in said one surface of the semiconductor layer.

34. A light emitting element, comprising:

a semiconductor layer that comprises a light emitting layer, a predetermined optical form that is provided on one surface of the semiconductor layer, the predetermined optical form being made to allow an increase in efficiency of taken out light from an inside of the light emitting element (LED element);

an electrode part that is provided on the other surface of semiconductor layer;

a light transmitting material layer that is provided on one surface of the semiconductor layer; and

a sealing material that seals the LED element, the sealing material comprising an SiO₂—

Nb₂O₅ based glass as a matrix material.

wherein the predetermined optical form is formed in a surface of the light transmitting material layer, and

the light transmitting material layer comprises GaN,

wherein the predetermined optical form is an uneven surface comprising a rectangular projection of different forms and different depths in a vertical cross section of the light transmitting material layer.

35. The light emitting element according to claim 34, wherein:

the electrode part comprises a p-electrode for med of ITO (indium tin oxide).