Luminescent ceramic for a light emitting device

• US 20050269582A1
• Filed: 06/03/2004
• Published: 12/08/2005
• Est. Priority Date: 06/03/2004
• Status: Active Grant

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Lumileds Lighting US LLC (Apollo Global Management, Inc.)
• Inventors: Bechtel, Hans-Helmut, Schmidt, Peter J., Krames, Michael R., Mueller-Mach, Regina B., Meyer, Joerg, Mueller, Gerd O., Kop, Theo Arnold, de Graaf, Jan
• Granted Patent: US 7,361,938 B2
• Time in Patent Office: Days
• US Class Current: 257/94
• CPC Class Codes: C04B 2235/3213 Strontium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3217 Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina
• CPC Class Codes: C04B 2235/3224 Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide
• CPC Class Codes: C04B 2235/3225 Yttrium oxide or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3229 Cerium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3286 Gallium oxides, gallates, indium oxides, indates, thallium oxides, thallates or oxide forming salts thereof, e.g. zinc gallate
• CPC Class Codes: C04B 2235/6027 Slip casting
• CPC Class Codes: C04B 2235/662 Annealing after sintering
• CPC Class Codes: C04B 35/44 based on aluminates
• CPC Class Codes: C04B 35/547 based on sulfides or selenides or tellurides
• CPC Class Codes: C04B 35/584 based on silicon nitride
• CPC Class Codes: C04B 35/597 based on silicon oxynitride, e.g. SIALONS
• CPC Class Codes: C04B 35/6268 characterised by the applied pressure or type of atmosphere, e.g. in vacuum, hydrogen or a specific oxygen pressure
• CPC Class Codes: C04B 35/64 Burning or sintering processes C04B33/32 takes precedence ; powder metallurgy B22F
• CPC Class Codes: C04B 35/645 Pressure sintering
• CPC Class Codes: C09K 11/7774 Aluminates
• 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 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2933/0041 relating to wavelength conversion elements
• CPC Class Codes: H01L 2933/005 relating to encapsulations
• CPC Class Codes: H01L 2933/0066 : relating to arrangements for conducting electric current to or from the semiconductor body
• CPC Class Codes: H01L 2933/0075 : relating to heat extraction or cooling elements
• CPC Class Codes: H01L 33/007 : comprising nitride compounds
• CPC Class Codes: H01L 33/0075 : comprising nitride compounds
• CPC Class Codes: H01L 33/0093 : Wafer bonding; Removal of the growth substrate
• CPC Class Codes: H01L 33/06 : within the light emitting region, e.g. quantum confinement structure or tunnel barrier
• CPC Class Codes: H01L 33/12 : with a stress relaxation structure, e.g. buffer layer
• CPC Class Codes: H01L 33/32 : containing nitrogen
• CPC Class Codes: H01L 33/50 : Wavelength conversion elements
• CPC Class Codes: H01L 33/501 : characterised by the materials, e.g. binder
• CPC Class Codes: H01L 33/502 : Wavelength conversion materials
• CPC Class Codes: H01L 33/505 : characterised by the shape, e.g. plate or foil
• CPC Class Codes: H01L 33/508 : having a non-uniform spatial arrangement or non-uniform concentration, e.g. patterned wavelength conversion layer, wavelength conversion layer with a concentration gradient of the wavelength conversion material
• CPC Class Codes: H01L 33/54 : having a particular shape
• CPC Class Codes: H01L 33/56 : Materials, e.g. epoxy or silicone resin
• CPC Class Codes: H01L 33/58 : Optical field-shaping elements
• CPC Class Codes: H01L 33/62 : Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls
• CPC Class Codes: H01L 33/641 : characterized by the materials
• CPC Class Codes: H01L 33/644 : in intimate contact or integrated with parts of the device other than the semiconductor body

Abstract

A semiconductor light emitting device comprising a light emitting layer disposed between an n-type region and a p-type region is combined with a ceramic layer which is disposed in a path of light emitted by the light emitting layer. The ceramic layer is composed of or includes a wavelength converting material such as a phosphor. Luminescent ceramic layers according to embodiments of the invention may be more robust and less sensitive to temperature than prior art phosphor layers. In addition, luminescent ceramics may exhibit less scattering and may therefore increase the conversion efficiency over prior art phosphor layers.

Claims

1. A structure comprising:

a semiconductor light emitting device comprising a light emitting layer disposed between an n-type region and a p-type region; and

a first ceramic layer disposed in a path of light emitted by the light emitting layer, the first ceramic layer comprising a wavelength converting material;

wherein the semiconductor light emitting device is attached to a host substrate, and the first ceramic layer is attached to a surface of the semiconductor light emitting device opposite the host substrate.

2. The structure of claim 1 wherein the first ceramic layer comprises a rigid agglomerate of phosphor particles.

3. The structure of claim 2 wherein the first ceramic layer is substantially free of binder material.

4. The structure of claim 2 wherein the first ceramic layer is formed by heating powder phosphor particles at a pressure greater than atmospheric pressure until a surface of the phosphor particles begins to soften and the phosphor particles stick together.

5. The structure of claim 1 further comprising an adhesive layer disposed between the first ceramic layer and the semiconductor light emitting device.

6. The structure of claim 5 wherein the adhesive layer is one of an organic adhesive, epoxy, silicone, an inorganic adhesive, and a sol-gel glass.

7. The structure of claim 5 wherein, the adhesive layer comprises one of glass having an index of refraction greater than 1.8, chalcogenide glass, (Ge,Sb,Ga)(S,Se) chalcogenide glass, a III-V semiconductor, GaP, InGaP, GaAs, GaN, a II-VI semiconductor, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, a group IV semiconductor, Si, Ge, an organic semiconductor, a metal oxide, tungsten oxide, titanium oxide, nickel oxide, zirconium oxide, indium tin oxide, and chromium oxide, a metal fluoride, magnesium fluoride, calcium fluoride, a metal, Zn, In, Mg, and Sn, yttrium aluminum garnet, a phosphide compound, an arsenide compound, an antimonide compound, a nitride compound, and a high index organic compound.

8. The structure of claim 5 wherein the first ceramic layer is substantially free of adhesive material.

9. The structure of claim 1 further comprising an interface between the semiconductor light emitting device and the first ceramic layer, the interface formed by pressing the semiconductor light emitting device and the first ceramic layer together at a temperature greater than room temperature and a pressure greater than atmospheric pressure.

10. The structure of claim 1 wherein a surface of the first ceramic layer comprises a lens.

11. The structure of claim 1 wherein a surface of the first ceramic layer comprises a dome.

12. The structure of claim 1 wherein a surface of the first ceramic layer comprises a Fresnel lens.

13. The structure of claim 1 wherein a surface of the first ceramic layer comprises a photonic crystal structure.

14. The structure of claim 1 wherein a surface of the first ceramic layer is textured.

15. The structure of claim 1 wherein the first ceramic layer comprises a phosphor doped with a dopant, wherein a concentration of dopant is graded.

16. The structure of claim 15 wherein:

the concentration is graded from a first concentration in a first portion of the first ceramic layer to a second concentration in a second portion of the first ceramic layer;

the first concentration is greater than the second concentration; and

the first portion is closer to the semiconductor light emitting device than the second portion.

19. The structure of claim 1 further comprising a second ceramic layer disposed in a path of light emitted by the light emitting layer.

20. The structure of claim 19 wherein:

the first ceramic layer comprises a first wavelength converting material; and

the second ceramic layer comprises a second wavelength converting material.

21. The structure of claim 19 wherein:

the first ceramic layer comprises a wavelength converting material; and

the second ceramic layer does not include a wavelength converting material.

22. The structure of claim 19 wherein a surface area of a surface of one of the first and second ceramic layers is greater than a surface area of a surface of the semiconductor light emitting device from which light is extracted from the device.

23. The structure of claim 1 wherein the wavelength converting material comprises one of (Lu_1-x-y-a-bY_xGd_y)₃(Al_1-xGa_x)₅O₁₂:

Ce_aPr_b wherein 0<

x<

1, 0<

y<

1, 0<

z≦

0.1, 0<

a≦

0.2 and 0<

b≦

0.1;

Lu₃Al₅O₁₂;

Ce³⁺ and Y₃Al₅O₁₂;

Ce³⁺.

24. The structure of claim 1 further comprising a dichroic filter disposed between the first ceramic layer and the semiconductor light emitting device.

17. A structure comprising:

a semiconductor light emitting device comprising a light emitting layer disposed between an n-type region and a p-type region; and

a first ceramic layer disposed in a path of light emitted by the light emitting layer, the first ceramic layer comprising a wavelength converting material;

wherein the semiconductor light emitting device comprises a growth substrate, and the first ceramic layer is attached to the growth substrate.

25. The structure of claim 17 wherein a surface of the first ceramic layer comprises a lens.

26. The structure of claim 17 wherein the first ceramic layer comprises a phosphor doped with a dopant, wherein a concentration of dopant is graded.

27. The structure of claim 17 wherein the wavelength converting material comprises one of (Lu_1-x-y-a-bY_xGd_y)₃(Al_1-zGa_z)₅O₁₂:

Ce_aPr_b wherein 0<

x<

1, 0<

y<

1, 0<

z≦

0.1, 0<

a≦

0.2 and 0<

b≦

0.1;

Lu₃Al₅O₁₂;

Ce³⁺; and

Y₃Al₅O₁₂;

Ce³⁺.

18. (canceled)

28. A structure comprising:

a ceramic layer comprising a wavelength converting material; and

a III-nitride structure grown over the ceramic layer, the III-nitride structure including a light emitting layer disposed between an n-type region and a p-type region.

29. A method comprising:

growing a III-nitride structure over a growth substrate, the III-nitride structure comprising a light emitting layer disposed between an n-type region and a p-type region; and

a bonding a ceramic layer comprising a wavelength converting material to a surface of the growth substrate.

30. The method of claim 29 wherein bonding comprises diffusion bonding in a uniaxial hot processing apparatus.

31. The method of claim 29 wherein bonding comprises heating the growth substrate and the ceramic layer.

32. The method of claim 29 wherein bonding comprises applying external pressure to the growth substrate and ceramic layer.