Light emitting device

• US 7,679,101 B2
• Filed: 11/30/2006
• Issued: 03/16/2010
• 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: Starick, Detlef, Roth, Gundula, Tews, Walter, Pachler, Peter, Hirano, Atsuo, Kempfert, Wolfgang, Ota, Akihito, Tasch, Stefan, Ota, Koichi
• Primary Examiner(s): Dickey; Thomas L
• Application Number:
  US11/606,170
• Publication Number:
  US 20070090383A1
• Time in Patent Office: 1,202 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, said light emitting element emitting a light with a wavelength of 300 to 500 nm;

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

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

a third phosphor which can absorb a part of said light emitted from the light emitting element and can emit a light with a wavelength different from the emitted light from the first phosphor and the second phosphor,

wherein a wavelength emitted from said first phosphor has a half bandwidth up to 110 nm,

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

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

said p-type cladding layer and said n-type cladding layer comprise a superlattice structure, and

the light emitting device emits a white light with, an Ra value>

72,

wherein the first to third phosphors are each suspended in separate matrices, and the matrices arc disposed back and forth in a light propagation direction.

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

the first phosphor comprises a divalent-europium-activated alkaline earth metal orthosilicate activated by a divalent europium.

3. The light emitting device according to claim 1, wherein the n-cladding layer and the p-cladding layer each comprises a superlattice structure comprising layers that have a thickness of not more than 100 angstroms and are different from each other in composition.

4. The light emitting device according to claim 1, wherein said quantum well structure comprises a well layer of InGaN and a barrier layer of GaN.

5. The light emitting device according to claim 1, wherein said quantum well structure comprises a well layer of InGaN and a barrier layer of AlGaN.

6. The 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 40 nm.

7. The light emitting device according to claim 1, wherein a band gap of said p-type cladding layer is larger than a band gap of said n-type cladding layer.

8. The light emitting device according to claim 1, wherein the light emitting device comprises at least three kinds of phosphor selected from a group including the first to third phosphor.

9. The light emitting device according to claim 1, wherein the third phosphor can emit a blue and/or green light.

10. A light emitting device, comprising:

a light emitting element comprising a nitride semiconductor, said light emitting element generating a blue light;

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

a second phosphor which can absorb a part of said blue light emitted from the light emitting element and can emit a red light with a wavelength different from that of said absorbed light,

wherein a wavelength emitted from said first phosphor has a half bandwidth up to 110 nm,

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

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

said p-type cladding layer and said n-type cladding layer comprise a superlattice structure, and

the light emitting device emits a white light with an Ra value>

72, wherein;

the first phosphor comprises a divalent-europium-activated alkaline earth metal orthosilicate represented by a formula;

(Sr_(1-x-y)Ba_xCa_y)₂Si<sub>(1-α

-β

-γ

-δ

)</sub>P_α

Al_β

B_γ

Ge_δ

)O₄;

Eu²⁺

where 0<

x≦

0.8, 0≦

y<

0.8, 0<

x+y<

1, 0≦

α

, β

, γ

,<

0.25, 0≦

δ

<

0.5, 0≦

α

+β

+γ

+δ

<

1 and /or

an alkali earth metal disilicate activated by divalent europium and/or manganese and represented by a formula;

Me_(3-x-y)MgSi₂O₃;

xEu, yMn

where 0.005<

x<

0.5, 0.005<

y<

0.5 and Me denotes at least one of strontium (Sr), barium (Ba), and calcium (Ca).

11. The light emitting device according to claim 10, wherein the phosphor further comprises monovalent ions, particularly halogenides.

12. A light emitting device, comprising:

a light emitting element comprising a nitride semiconductor, said light emitting element generating a blue light;

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

a second phosphor which can absorb a part of said blue light emitted from the light emitting element and can emit a red light with a wavelength different from that of said absorbed light,

wherein the first phosphor comprises a divalent-europium-activated alkaline earth metal orthosilicate represented by a formula;

(Sr_(1-x-y)Ba_xCa_y)₂Si<sub>(1-α

-β

-γ

-δ

)</sub>P_α

Al_β

B_γ

Ge_δ

)O₄;

Eu²⁺

 

where 0<

x≦

0.8, 0≦

y<

0.8, 0<

x+y<

1, 0≦

α

, β

, γ

,<

0.25, 0≦

δ

<

0.5, 0≦

α

+β

+γ

+δ

<

1.

13. A backlight device of a liquid crystal panel comprising the light emitting device according to claim 12.

14. The backlight device according to claim 13, 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 first and second phosphors are provided in a sheet form on the light output surface of the light guide plate.