Light emitting device having phosphor of alkaline earth metal silicate

• US 6,943,380 B2
• Filed: 12/28/2001
• Issued: 09/13/2005
• Est. Priority Date: 12/28/2000
• Status: Expired due to Term

• 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: Pachler, Peter, Starick, Detlef, Roth, Gundula, Tews, Walter, Tasch, Stefan, Ota, Koichi, Hirano, Atsuo, Kempfert, Wolfgang, Ota, Akihito
• Primary Examiner(s): Tran, Minhloan
• Assistant Examiner(s): Dickey, Thomas L.
• Application Number:
  US10/451,864
• Publication Number:
  US 20040051111A1
• Time in Patent Office: 1,355 Days
• Field of Search: 257 13- 18, 257/20, 257/22, 257 76- 82, 257/84, 257 94- 96, 257 98-103, 313456-473, 313/505, 372 10- 14, 372 66- 75
• US Class Current: 257/100
• 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 a divalent-europium-activated alkaline earth metal silicate represented by the formula;

(2-x-y)SrO.x(Ba, Ca)O.(1-a-b-c-d)SiO₂.aP₂O₅ bAl₂O₃ 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

a divalent-europium-activated alkaline earth metal silicate represented by the formula;

(2-x-y)BaO.x(Sr, Ca)O.(1-a-b-c-d)SiO₂.aP₂O₅ bAl₂O₃ cB₂O₃ dGeO₂;

y Eu²⁺

wherein 0.01<

x<

1.6,

0.005<

y<

0.5, and

0<

a, b, c, and d<

0.5.

2. A light emitting device according to claim 1, wherein

said phosphor comprises an orthosilicate, at least one of a, b, c, and d is greater than 0.01.

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

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

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

said covering member comprises silicone resin.

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

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

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

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

said covering member comprises epoxy resin.

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

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

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

said covering member comprises low-melting glass.

11. A light emitting device according to claim 10, 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.

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

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

13. A light emitting device according to claim 3, 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.

14. A light emitting device according to claim 13, wherein:

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

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

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

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

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

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

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

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

said p-type clad layer comprises Al_xGa_1-xN where 0<

x<

1, and

said n-type clad layer comprises Al_yGa_1-yN where O<

y<

1.

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

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

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

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

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

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

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

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

23. A light emitting device according to claim 22, wherein:

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

24. A light emitting device according to claim 22, wherein:

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

25. A light emitting device according to claim 22, wherein:

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

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

26. A light emitting device according to claim 22, wherein:

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

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

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

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

said p-type clad layer comprises Al_xGa_1-xN where 0<

x<

1, and

said n-type clad layer comprises Al_yGa_1-yN where 0<

y<

1.

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

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

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

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

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

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

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

said light emitting element has been fixed onto a frame with the aid of an insulating adhesive.

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

said adhesive is colorless and transparent.

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

said adhesive contains said phosphor that comprises a material selected from alkaline earth metal silicate.

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

said adhesive contains said phosphor that comprises a material selected from alkaline earth metal silicate.

36. 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.

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

said substrate comprises sapphire.

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

said light emitting element comprises a light reflecting layer.

39. A light emitting device according to claim 38, wherein:

said light reflecting layer is provided on a surface of the substrate opposite to the surface of the substrate on which an active layer is stacked.

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

said light reflecting layer comprises aluminum.

41. A light emitting device according to claim 38, wherein:

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

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

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

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

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

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

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

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

said light emitting clement 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.

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

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

47. A light emitting device according to claim 46, wherein:

said protective element comprises a Zener diode or a capacitor.

48. A light emitting device according to claim 46, wherein:

said protective element comprises a submount formed of a Zener diode, and

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

49. 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 a wavelength different from that of said absorbed light,

wherein said phosphor comprises alkaline earth metal silicate, said light emitting element has been fixed onto a frame with the aid of an insulating adhesive, and

said adhesive is white.

50. The light emitting device according to claim 49, wherein:

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

51. The light emitting device according to claim 50, wherein:

said covering member comprises a silicon resin.

52. The light emitting device according to claim 51, wherein:

said covering member comprises a low-melting glass.

53. The light emitting device according to claim 49, 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.

54. 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 a wavelength different from that of said absorbed light,

wherein said phosphor comprises alkaline earth metal silicate, and a half-value width of a wavelength emitted from said light emitting element is not more than 40 nm.

55. The light emitting device according to claim 54, wherein:

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

56. The light emitting device according to claim 55, wherein:

said covering member comprises a silicon resin.

57. The light emitting device according to claim 55, wherein:

said covering member comprises a low-melting glass.

58. The light emitting device according to claim 54, 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.

59. The light emitting device according to claim 54, wherein:

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

60. The light emitting device according to claim 54, wherein:

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