Light emitting device including luminescent ceramic and light-scattering material
View Patent ↗A ceramic body comprising a wavelength converting material is disposed in the path of light emitted by the light emitting region of a semiconductor structure comprising a light emitting region disposed between an n-type region and a p-type region. A layer of transparent material is also disposed in the path of light emitted by the light emitting region. The transparent material may connect the ceramic body to the semiconductor structure. Particles configured to scatter light emitted by the light emitting region are disposed in the layer of adhesive material. In some embodiments the particles are phosphor; in some embodiments the particles are not a wavelength-converting material.
1. A device comprising:
a semiconductor structure comprising a light emitting region disposed between an n-type region and a p-type region;
a ceramic body comprising a wavelength converting material, the ceramic body being disposed in a path of light emitted by the light emitting region; and
a layer of transparent material disposed in a path of light emitted by the light emitting region, wherein a plurality of particles configured to scatter light emitted by the light emitting region are disposed in the layer of transparent material.
2. The device of claim 1 wherein the transparent material is disposed between the semiconductor structure and the ceramic body and connects the semiconductor structure to the ceramic body.
3. The device of claim 1 wherein the ceramic body is disposed between the transparent material and the semiconductor structure.
4. The device of claim 1 wherein a thickness of the transparent material is less than 50% a thickness of the ceramic body.
5. The device of claim 1 wherein a difference between an index of refraction of the particles and an index of refraction of the transparent material is at least 0.4.
6. The device of claim 1 wherein the particles are selected from the group of oxides of yttrium, oxides of titanium, oxides of strontium, and oxides of rubidium.
7. The device of claim 1 wherein the particles have an average diameter between 0.5λ and 20λ, where λ is the wavelength of light emitted by the light emitting region within the semiconductor structure.
8. The device of claim 1 wherein the transparent material is selected from the group of silicone, epoxy, and glass.
9. The device of claim 1 wherein the layer of transparent material has a thickness between 0.5 and 50 μm.
10. The device of claim 1 wherein the semiconductor structure comprises a plurality of III-nitride layers.
11. A device comprising:
a semiconductor structure comprising a light emitting region disposed between an n-type region and a p-type region;
a ceramic body comprising a first wavelength converting material, the ceramic body being disposed in a path of light emitted by the light emitting region; and
a layer of transparent material disposed in a path of light emitted by the light emitting region, wherein a plurality of particles of a second wavelength converting material are disposed in the layer of transparent material.
12. The device of claim 11 wherein the transparent material is disposed between the semiconductor structure and the ceramic body and connects the semiconductor structure to the ceramic body.
13. The device of claim 11 wherein the ceramic body is disposed between the transparent material and the semiconductor structure.
14. The device of claim 11 wherein a thickness of the transparent material is less than 50% a thickness of the ceramic body.
15. The device of claim 11 wherein the light emitting region is configured to emit blue light, the first wavelength converting material is configured to absorb blue light and emit yellow or green light, and the second wavelength converting material is configured to absorb blue light and emit red light.
16. The device of claim 11 wherein the first wavelength converting material is selected from the group of (Lu 1−x−y−a−b Y x Gd y ) 3 (Al 1−z Ga z ) 5 O 12 :Ce a Pr b wherein 0<x<1, 0<y<1, 0<z≦0.1, 0<a≦0.2 and 0<b≦0.1; Lu 3 Al 5 O 12 :Ce 3+ ; Y 3 Al 5 O 12 :Ce 3+ ; SrSi 2 N 2 O 2 :Eu 2+ ; (Sr 1−u−v−x Mg u Ca v Ba x )(Ga 2−y−z Al y In z S 4 ):Eu 2+ ; SrGa 2 S 4 :Eu 2+ ; and Sr 1−x Ba x SiO 4 :Eu 2+ .
17. The device of claim 11 wherein the second wavelength converting material is selected from the group of (Ca 1−x Sr x )S:Eu 2+ wherein 0<x≦1; CaS:Eu 2+ ; SrS:Eu 2+ ; (Sr 1−x−y Ba x Ca y ) 2−z Si 5−a Al a N 8−a O a :Eu z 2+ wherein 0≦a<5, 0<x≦1, 0≦y≦1, and 0<z≦1; Sr 2 Si 5 N 8 :Eu 2+ ; Ca 0.99 AlSiN 3 :Eu 0.01 ; Ba 2−x−z M x Si 5−y Al y N 8−y O y :Eu z (M=Sr, Ca; 0≦x≦1, 0≦y≦4, 0.0005≦z≦0.05); and Sr 1−x Si 2 O 2 N 2 :Eu 2+ .
18. The device of claim 11 further comprising a plurality of non-wavelength-converting particles disposed in the layer of transparent material.
19. The device of claim 11 wherein the transparent material is selected from the group of silicone, epoxy, and glass.
20. The device of claim 11 wherein the transparent material has a thickness between 0.5 and 50 μm.
21. The device of claim 11 wherein the semiconductor structure comprises a plurality of III-nitride layers.
22. The device of claim 11 further comprising:
n- and p-contacts electrically connected to the n- and p-type regions; and
a cover disposed over the light emitting region.