Light emitting device

• US 20040051111A1
• Filed: 06/30/2003
• Published: 03/18/2004
• Est. Priority Date: 12/28/2000
• Status: Active Grant

• Current Assignee: Leuchtstoffwerk Breitungen GmbH, Litec Gbr, Toyoda Gosei Company Limited (Toyota Motor Corporation), Tridonic Optoelectronics GmbH
• Original Assignee: Leuchtstoffwerk Breitungen GmbH, Litec Gbr, Toyoda Gosei Company Limited (Toyota Motor Corporation), Tridonic Optoelectronics GmbH
• Inventors: Starick, Detlef, Roth, Gundula, Tews, Walter, Tasch, Stefan, Pachler, Peter, Ota, Koichi, Hirano, Atsuo, Kempfert, Wolfgang, Ota, Akihito
• Granted Patent: US 6,943,380 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: C09K 11/7734 Aluminates
• CPC Class Codes: C09K 11/77344 Aluminosilicates
• CPC Class Codes: C09K 11/774 Borates
• CPC Class Codes: C09K 11/7795 Phosphates
• CPC Class Codes: F21Y 2105/10 comprising a two-dimensional array of point-like light-generating elements
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: G02B 6/0036 2-D arrangement of prisms, protrusions, indentations or roughened surfaces
• CPC Class Codes: G02B 6/0073 Light emitting diode [LED]
• CPC Class Codes: H01L 2224/16145 the bodies being stacked
• CPC Class Codes: H01L 2224/32245 the item being metallic
• CPC Class Codes: H01L 2224/32257 the layer connector connecting to a bonding area disposed in a recess of the surface of the item
• CPC Class Codes: H01L 2224/45139 Silver (Ag) as principal constituent
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• 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 2224/48257 connecting the wire to a die pad of the item
• CPC Class Codes: H01L 2224/49107 on the semiconductor or solid-state body
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• CPC Class Codes: H01L 2924/00 : Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• 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 2924/00012 : 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 2924/01049 : Indium [In]
• CPC Class Codes: H01L 2924/181 : Encapsulation
• 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 33/06 : within the light emitting region, e.g. quantum confinement structure or tunnel barrier
• CPC Class Codes: H01L 33/32 : containing nitrogen
• CPC Class Codes: H01L 33/502 : Wavelength conversion materials
• CPC Class Codes: H01L 33/507 : the elements being in intimate contact with parts other than the semiconductor body or integrated with parts other than the semiconductor body
• CPC Class Codes: Y02B 20/00 : Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

The light emitting device has a light emitting diode which is made of a nitride semiconductor and a phosphor which absorbs a part of lights emitted from the light emitting diode and emits different lights with wavelengths other than those of the absorbed lights. The phosphor is made of alkaline earth metal silicate fluorescent material activated with europium.

Claims

1. A light emitting device, comprising:

a light emitting element comprising a nitride semiconductor; and

a phosphor which can absorb a part of light emitted from said light emitting element and can emit light of wavelength different from that of said absorbed light, wherein;

said phosphor comprises alkaline earth metal silicate.

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

said phosphor is divalent-europium-activated alkaline earth metal orthosilicate represented by formula;

(2 - x - y)SrO.x(Ba,Ca)O.(1 - a - b - c - d)SiO₂.aP₂O₅bAl₂O₃ cB₂O₃ dGeO₂;

y Eu²⁺

wherein 0<

x<

1.6,

0.005<

y<

0.5, and

0<

a, b, c, and d<

0.5, and/or

divalent-europium-activated alkaline earth metal orthosilicate represented by formula;

(2 - x - y)BaO.x(Sr,Ca)O.(1 - a - b - c - d)SiO₂.aP₂O₅bAl₂O₃ cB₂O₃ dGeO₂;

y Eu²⁺

wherein 0.01<

x<

1.6,

0.005<

y<

0.5, and

0<

a, b, c, and d<

0.5,

with the proviso that at least one of a, b, c, and d values is advantageously greater than 0.01.

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

said phosphor is mixed into a covering member which covers said light emitting element.

5. A light emitting device according to claim 4, wherein:

said covering member comprises silicone resin.

6. A light emitting device according to claim 4, wherein:

said covering member comprises epoxy resin.

7. A light emitting device according to claim 4, wherein:

said covering member comprises low-melting glass.

8. A light emitting device according to any one of claims 4 to 7, wherein:

said phosphor is mixed with a covering member which covers said light emitting element and a scattering agent is also mixed with the covering member.

9. A light emitting device according to any one of claims 4 to 8, wherein:

said covering member is further covered by a second transparent covering member.

10. A light emitting device according to claim 1, wherein:

said light emitting element comprises a light emitting layer containing indium.

11. A light emitting device according to claim 1 or 10, wherein:

said light emitting element comprises a double hetero structure comprising a light emitting layer sandwiched between a p-type clad layer and an n-type clad layer.

12. A light emitting device according to claim 11, wherein:

said p-type clad layer is formed of Al_xGa_1-xN where 0<

x<

1, and

said n-type clad layer is formed of Al_yGa_1-yN where 0≦

y<

1.

13. A light emitting device according to claim 11 or 12, wherein:

the band gap of said p-type clad layer is larger than that of said n-type clad layer.

14. A light emitting device according to claim 10, wherein:

said light emitting layer of said light emitting element comprises a quantum well structure.

15. A light emitting device according to claim 14, wherein:

said quantum well structure comprises a well layer of InGaN and a barrier layer of GaN.

16. A light emitting device according to claim 14, wherein:

said quantum well structure comprises a well layer of InGaN and a barrier layer of AlGaN.

17. A light emitting device according to claim 14, wherein:

said quantum well structure comprises a well layer of AlInGaN and a barrier layer of AlInGaN, and

the band gap energy of said barrier layer is larger than that of said well layer.

18. A light emitting device according to claim 14, wherein:

said well layer has a thickness of not more than 100 angstroms.

19. A light emitting device according to claim 1, wherein:

said p-type clad layer and/or said n-type clad layer have a superlattice structure formed stacking nitride semiconductor layers that are different from each other or one another in composition.

20. A light emitting device according to claim 1, wherein:

said light emitting element is fixed onto a frame using an insulating adhesive.

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

said adhesive is colorless and transparent.

22. A light emitting device according to claim 20 or 21, wherein:

said adhesive contains said phosphor that comprises a material selected from said groups of alkaline earth metal silicates.

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

said adhesive is white.

24. A light emitting device according to claim 1, wherein:

said light emitting element comprises a transparent substrate and a nitride semiconductor grown by vapor phase epitaxy on said transparent substrate.

25. A light emitting device according to claim 24, wherein:

said substrate is of sapphire.

26. A light emitting device according to claim 24, wherein:

said light emitting element comprises a light reflecting layer.

27. A light emitting device according to claim 26, wherein:

said light reflecting layer is provided on a surface of the substrate opposite to the surface of the substrate on which the light emitting layer is formed.

28. A light emitting device according to claim 27, wherein:

said light reflecting layer is of aluminum.

29. A light emitting device according to claim 24, wherein:

said light reflecting layer comprises multiple GaN-based thin layers.

30. A light emitting device according to claim 1, wherein:

the half-value width of a wavelength emitted from said light emitting element is not more than 50 nm.

31. A light emitting device according to claim 1, wherein:

the half-value width of a wavelength emitted from said light emitting element is not more than 40 nm.

32. A light emitting device according to claim 1, wherein:

said light emitting element has a peak emission wavelength of 380 nm to 500 nm.

33. A light emitting device according to claim 1, wherein:

said phosphor has a main emission wavelength which is longer than the main peak emission wavelength of said light emitting element.

34. A light emitting device according to claim 1, wherein:

said light emitting element comprises a substantially rectangular light guide plate such that light emitted from the light emitting element is introduced thereinto and is output from its light output surface, and

said phosphor is provided in a sheet form on the light output surface of said light guide plate.

39. A light emitting device according to claim 1, further comprising:

a protection element for protecting said light emitting element from static electricity.

40. A light emitting device according to claim 39, wherein:

said protection element is a Zener diode or a capacitor.

41. A light emitting device according to claim 39, wherein:

said protection element is a submount formed of a Zener diode, and

said light emitting element is provided on said submount, and said phosphor covers the periphery of said light emitting element.

2. A light emitting device wherein:

said phosphor comprises europium-activated alkaline earth metal silicate.

35. A light emitting device, comprising:

a light emitting element of a GaN semiconductor disposed in a cup of a mount lead;

a phosphor which can absorb a part of light emitted from said light emitting element and can emit light of wavelength different from that of said absorbed light;

a coating member with which the inside of said cup has been filled, said coating member comprising a sealant containing said phosphor; and

a mold member which covers said coating member, said light emitting element, and the tip portion of said mount lead, wherein;

said phosphor comprises a member selected from groups of alkaline earth metal silicates.

37. A light emitting device according to claim 35 or 36, wherein:

said light emitting element has, on its one side, a p-side electrode and an n-side electrode and is provided on a metal frame, said p-side electrode and said n-side electrode each have been wire bonded by gold wire, and said light emitting element emits blue light upon the application of a voltage supplied via said gold wire.

38. A light emitting device according to claim 35 or 36, wherein:

said light emitting element is provided within said cup, and said phosphor is provided so as to cover said light emitting element and to locate at a position below the upper edge of the cup.

36. A light emitting device, comprising:

a casing;

a light emitting element comprising a LED chip which has been mounted within said casing by flip-chip bonding, said LED chip being formed of a GaN compound semiconductor;

a phosphor which can absorb a part of light emitted from said LED chip and can emit light of wavelength different from that of said absorbed light; and

a mold member with which the inside of the LED chip-mounted casing has been filled, said mold member comprising a transparent sealant containing said phosphor, wherein;

said phosphor comprises a member selected from groups of alkaline earth metal silicates, and said light emitting device radiates white light as a result of mixing of said light emitted from said LED chip with said light emitted from said phosphor.

42. A light emitting device, comprising:

a light emitting element of a GaN compound semiconductor provided in a cup of a mount lead;

a phosphor which can absorb a part of light emitted from said light emitting element and can emit light of wavelength different from that of said absorbed light; and

a mold member which covers said light emitting element and the tip portion of said mount lead, wherein;

said phosphor comprises a member selected from groups of alkaline earth metal silicates and is contained in a resin base material constituting a phosphor cover which covers said mold member.