Multi-grain luminescent ceramics for light emitting devices

• US 7,902,564 B2
• Filed: 12/22/2006
• Issued: 03/08/2011
• Est. Priority Date: 12/22/2006
• Status: Expired due to Fees

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.), Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Philips Lumileds Lighting Company LLC (Apollo Global Management, Inc.), Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Bechtel, Hans-Helmut, Schmidt, Peter J., Krames, Michael R., Mueller-Mach, Regina B., Mueller, Gerd O.
• Primary Examiner(s): SAYADIAN, HRAYR
• Application Number:
  US11/615,372
• Publication Number:
  US 20080149956A1
• Time in Patent Office: 1,537 Days
• Field of Search: 257/79, 257/80, 257/98, 257/102, 257/E33.061, 257/E31.002, 257/E31.093, 257/E31.095, 257/E31.096, 257/E31.129, 250/493.1, 250/505.1, 250/909, 25230116-3014 H, 313/483, 313/485, 313/486, 313502-504
• US Class Current: 257/98
• CPC Class Codes: C04B 2235/3206 Magnesium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3208 Calcium oxide or oxide-forming salts thereof, e.g. lime
• CPC Class Codes: C04B 2235/3213 Strontium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3215 Barium oxides or oxide-forming salts thereof
• 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 2235/3409 Boron oxide, borates, boric acids, or oxide forming salts thereof, e.g. borax
• CPC Class Codes: C04B 2235/3418 Silicon oxide, silicic acids, or oxide forming salts thereof, e.g. silica sol, fused silica, silica fume, cristobalite, quartz or flint glass constituents C04B2235/36
• CPC Class Codes: C04B 2235/652 Reduction treatment C04B2235/664 takes precedence
• CPC Class Codes: C04B 2235/658 Atmosphere during thermal treatment
• CPC Class Codes: C04B 2235/6582 Hydrogen containing atmosphere
• CPC Class Codes: C04B 2235/77 Density
• CPC Class Codes: C04B 35/44 based on aluminates
• CPC Class Codes: C04B 35/597 based on silicon oxynitride, e.g. SIALONS
• CPC Class Codes: C09K 11/7774 Aluminates
• CPC Class Codes: C09K 11/77748 Silicon Aluminium Nitrides or Silicon Aluminium Oxynitrides
• 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 2933/0091 : Scattering means in or on the semiconductor body or semiconductor body package H01L33/22 takes precedence
• CPC Class Codes: H01L 33/382 : the electrode extending partially in or entirely through the semiconductor body
• CPC Class Codes: H01L 33/501 : characterised by the materials, e.g. binder
• CPC Class Codes: Y10S 250/909 : Methods and apparatus ancillary to stimulable phosphor systems

Abstract

A ceramic body is disposed in a path of light emitted by a light source. The light source may include a semiconductor structure comprising a light emitting region disposed between an n-type region and a p-type region. The ceramic body includes a plurality of first grains configured to absorb light emitted by the light source and emit light of a different wavelength, and a plurality of second grains. For example, the first grains may be grains of luminescent material and the second grains may be grains of a luminescent material host matrix without activating dopant.

Claims

1. A device comprising:

a light source; and

a ceramic body disposed in a path of light emitted by the light source, wherein the ceramic body comprises;

a plurality of first grains, each of the first grains comprising a host matrix and an activating dopant configured to absorb first light emitted by the light source and emit second light of a different wavelength from the first light;

a plurality of second grains, each of the second grains comprising the host matrix without any activating dopant,

wherein the first and second grains have a grain size between 0.2 μ

m and 20 μ

m, and each of the first grains is surrounded by a ceramic matrix of the second grains.

2. The device of claim 1 wherein the light source comprises a semiconductor structure comprising a light emitting region disposed between an n-type region and a p-type region.

3. The device of claim 2 wherein the ceramic body is configured to scatter light emitted by the light emitting region.

4. The device of claim 2 wherein the second grains are transparent to the first light.

5. The device of claim 1 wherein the activating dopant is Ce.

6. The device of claim 2 wherein the first grains are dispersed over a plurality of regions in the ceramic body, wherein the plurality of regions are separated by second grains.

7. The device of claim 6 wherein:

the first grains comprise a host matrix and an activating dopant; and

within a region of first grains, a first grain proximate a center of the region has a higher concentration of activating dopant than a first grain proximate an edge of the region.

8. The device of claim 2 wherein the ceramic body is disposed on a surface of the semiconductor structure.

9. The device of claim 2 wherein the first light is blue and the second light is yellow or green.

10. The device of claim 2 wherein the first grains are (Lu₁₋

x−

y−

a−

bY_xGd_y)₃(Al<sub>1−

z−

u</sub>Ga_zSi_u)₅O<sub>12−

u</sub>N_u;

Ce_aPr_b wherein 0≦

x≦

1, 0≦

y≦

1, 0<

z≦

0.1, 0≦

u≦

0.2, 0<

a≦

0.2 and 0<

b≦

0.1.

11. The device of claim 2 wherein the first light is blue and the second light is red.

12. The device of claim 2 wherein the first grains are (Ca₁₋

x−

y−

zSr_xBa_yMg_z)<sub>1−

n</sub>Al_1+a+bSi<sub>1−

a−

b</sub>N<sub>3−

b</sub>O_b;

M_n wherein 0≦

x≦

1, 0≦

y≦

1,0≦

z≦

1, 0≦

a≦

1, 0≦

b ≦

1, 0≦

n≦

1, a≦

n, and M is a metal selected from the group of Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu or mixtures thereof.

13. The device of claim 2 wherein the first grains are Ca(Al,Si)₂N₃.

14. The device of claim 2 further comprising a wavelength converting material disposed in a path of light emitted by the light emitting region, the wavelength converting material being configured to absorb the first light and emit third light of a different wavelength from the first light.

15. The device of claim 2 further comprising:

first and second contacts electrically connected to the n-type region and the p-type region; and

a cover disposed over the light emitting region.

16. The device of claim 2 wherein the semiconductor structure comprises a plurality of III-nitride semiconductor layers.

17. The device of claim 1 wherein the activating dopant is Eu.

18. The device of claim 14 wherein:

the ceramic body is a first ceramic body; and

the wavelength converting material is included in a second ceramic body.