Wavelength-Converted Semiconductor Light Emitting Device

Abstract

A material such as a phosphor is optically coupled to a semiconductor structure including a light emitting region disposed between an n-type region and a p-type region, in order to efficiently extract light from the light emitting region into the phosphor. The phosphor may be phosphor grains in direct contact with a surface of the semiconductor structure, or a ceramic phosphor bonded to the semiconductor structure, or to a thin nucleation structure on which the semiconductor structure may be grown. The phosphor is preferably highly absorbent and highly efficient. When the semiconductor structure emits light into such a highly efficient, highly absorbent phosphor, the phosphor may efficiently extract light from the structure, reducing the optical losses present in prior art devices.

1 . A light emitting device comprising:
 a semiconductor structure comprising a plurality of layers including a light emitting region sandwiched between and n-type region and a p-type region and;   a luminescent material in direct contact with one of the plurality of layers, wherein at a wavelength of light emitted by the light emitting region, the imaginary component k of a refractive index of the luminescent material is greater than 0.01.   
   
   
       2 . The light emitting device of  claim 1  wherein k is greater than 0.1. 
   
   
       3 . The light emitting device of  claim 1  wherein the light emitting region comprises III-nitride material. 
   
   
       4 . The light emitting device of  claim 1  wherein the luminescent material comprises phosphor. 
   
   
       5 . The light emitting device of  claim 4  wherein the luminescent material comprises a ceramic phosphor. 
   
   
       6 . The light emitting device of  claim 4  wherein the luminescent material comprises phosphor grains. 
   
   
       7 . The light emitting device of  claim 6  further comprising a transparent material disposed over the phosphor grains, the transparent material having an index of refraction greater than 1.7. 
   
   
       8 . The light emitting device of  claim 7  wherein the transparent material comprises glass. 
   
   
       9 . The light emitting device of  claim 8  wherein the glass comprises a sol-gel glass. 
   
   
       10 . The light emitting device of  claim 7  further comprising nanoparticles having diameters between about 2 nm to about 50 nm disposed in the transparent material. 
   
   
       11 . The light emitting device of  claim 6  wherein a surface one of the plurality of layers in direct contact with the phosphor grains is textured or roughened. 
   
   
       12 . The light emitting device of  claim 1  wherein:
 the semiconductor structure is bonded to a package element having a lateral extent exceeding a lateral extent of the semiconductor structure; and   the package element is separated from the luminescent material by less than one hundred microns.   
   
   
       13 . A structure comprising:
 a ceramic body; and   a nucleation structure thinner than one hundred microns; and   a bonded interface that connects the ceramic body to the nucleation structure, the bonded interface being disposed between the ceramic body and the nucleation layer; wherein:
 the nucleation structure is configured such that an epitaxial structure may be grown on the nucleation structure; and 
 any separation between the ceramic body and the nucleation structure is less than one hundred microns. 
   
   
   
       14 . The structure of  claim 13  further comprising a semiconductor structure grown on the nucleation structure, the semiconductor structure comprising a light emitting region disposed between an n-type region and a p-type region, the light emitting region being configured to emit light of the first peak wavelength, wherein the nucleation structure is disposed between the semiconductor structure and the ceramic body. 
   
   
       15 . The structure of  claim 14  the ceramic body comprises a phosphor configured to absorb light of a first peak wavelength and emit light of a second peak wavelength. 
   
   
       16 . The structure of  claim 14  wherein the nucleation structure is selected from the group of GaN, AlN, SiC, and Al 2 O 3 . 
   
   
       17 . A structure comprising:
 a package element;   a ceramic body; and   a semiconductor structure disposed between and connected to the ceramic body and the package element, the semiconductor structure comprising a light emitting region disposed between an n-type region and a p-type region, the light emitting region being configured to emit light of the first peak wavelength;   wherein the package element is separated from the ceramic body by less than one hundred microns and the package element has a lateral extent exceeding a lateral extent of the semiconductor structure.   
   
   
       18 . The structure of  claim 17  wherein the ceramic body comprises a phosphor configured to absorb light of a first peak wavelength and emit light of a second peak wavelength.