Luminescent ceramic for a light emitting device

• US 9,359,260 B2
• Filed: 02/20/2008
• Issued: 06/07/2016
• Est. Priority Date: 06/03/2004
• Status: Active Grant

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Inventors: Mueller, Gerd O., Mueller-Mach, Regina B., Krames, Michael R., Schmidt, Peter J., Bechtel, Hans-Helmut, Meyer, Joerg, de Graaf, Jan, Kop, Theo Arnold
• Primary Examiner(s): Ngo, Ngan
• Application Number:
  US12/034,588
• Publication Number:
  US 20080138919A1
• Time in Patent Office: 3,030 Days
• Field of Search: 257/98, 257/E33.061, 257/E33.068
• US Class Current: 1/1
• 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 device comprising:

a light emitting structure comprising a light emitting layer;

a first ceramic phosphor disposed in a path of light emitted by the light emitting layer;

a second ceramic phosphor disposed in a path of light emitted by the light emitting layer; and

a heat extraction structure;

wherein;

one of the first ceramic phosphor and the second ceramic phosphor is directly connected to the heat extraction structure;

a surface of the first ceramic phosphor is roughened;

one of the first ceramic phosphor and the second ceramic phosphor is a transparent or translucent ceramic slab formed by sintering;

the light emitting structure is disposed between a mount and the first ceramic phosphor and directly connected to the mount; and

the heat extraction structure is disposed between the mount and the first ceramic phosphor and directly connected to the mount.

2. The device of claim 1 wherein the second ceramic phosphor is disposed between the first ceramic phosphor and the light emitting structure.

3. The device of claim 1 wherein the first ceramic phosphor and the second ceramic phosphor are different phosphors.

4. The device of claim 1 wherein one of the first ceramic phosphor and the second ceramic phosphor is formed by heating powder phosphor particles until surfaces of the phosphor particles melt and stick together to form a rigid agglomerate of phosphor particles.

5. The device of claim 1 wherein one of the first ceramic phosphor and the second ceramic phosphor comprises a ceramic slab that is substantially free of binder material other than the phosphor itself.

6. The device of claim 1 wherein one of the first ceramic phosphor and the second ceramic phosphor comprises a ceramic slab with very little space or material with a refractive index different from a refractive index of a phosphor that forms the ceramic slab.

7. The device of claim 1 wherein the heat extraction structure is disposed adjacent to the light emitting structure and is spaced apart from the light emitting structure.

8. The device of claim 1 wherein the heat extraction structure comprises one of metal, Cu foil, Mo, Cu/Mo, Cu/W, ceramic, and compressed diamond.

9. The device of claim 1 wherein the first ceramic phosphor is wider than the second ceramic phosphor.

10. The device of claim 1 wherein the light emitting structure is a flip chip device.

11. A device comprising:

a light emitting structure comprising a light emitting layer;

a first ceramic phosphor disposed in a path of light emitted by the light emitting layer;

a second ceramic phosphor disposed in a path of light emitted by the light emitting layer; and

a heat extraction structure;

wherein;

one of the first ceramic phosphor and the second ceramic phosphor is directly connected to the heat extraction structure;

the first ceramic phosphor is textured;

one of the first ceramic phosphor and the second ceramic phosphor is a transparent or translucent ceramic slab formed by sintering;

the light emitting structure is disposed between a mount and the first ceramic phosphor and directly connected to the mount; and

the heat extraction structure is disposed between the mount and the first ceramic phosphor and directly connected to the mount.

12. The device of claim 11 wherein the first ceramic phosphor is textured with a photonic crystal structure.

13. The device of claim 11 wherein the first ceramic phosphor is textured with a Fresnel lens structure.

14. The device of claim 11 wherein the heat extraction structure is disposed adjacent to the light emitting structure and is spaced apart from the light emitting structure.

15. The device of claim 11 wherein the heat extraction structure comprises one of metal, Cu foil, Mo, Cu/Mo, Cu/W, ceramic, and compressed diamond.

16. The device of claim 11 wherein the first ceramic phosphor is wider than the second ceramic phosphor.

17. The device of claim 11 wherein the light emitting structure is a flip chip device.