Semiconductor light emitting device, wafer, and method for manufacturing nitride semiconductor crystal layer

Abstract

According to one embodiment, a semiconductor light emitting device includes a first semiconductor layer, a light emitting layer, a second semiconductor layer, and a low refractive index layer. The first semiconductor layer has a first major surface and a second major surface being opposite to the first major surface. The light emitting layer has an active layer provided on the second major surface. The second semiconductor layer is provided on the light emitting layer. The low refractive index layer covers partially the first major surface and has a refractive index lower than the refractive index of the first semiconductor layer.

1 - 15 . (canceled) 
     
     
         16 . A semiconductor light emitting device, comprising:
 a first semiconductor layer having a first major surface and a second major surface opposite to the first major surface, the first major surface forming a light extraction face, the first major surface including a first region and a second region, the first region having a rough surface including a convex part and a concave part, and the first semiconductor layer made of a nitride semiconductor crystal;   a light emitting layer having an active layer and provided on the second major surface;   a second semiconductor layer provided on the light emitting layer;   a low refractive index layer in contact with the convex part, the low refractive index layer not covering the concave part, the low refractive index layer made of a nitride semiconductor crystal, and the low refractive index layer having a refractive index lower than the refractive index of the first semiconductor layer; and   an electrode provided on the first semiconductor layer in the second region.   
     
     
         17 . The device according to  claim 16 , wherein a lattice of the low refractive index layer is continuous with a lattice of the first semiconductor layer. 
     
     
         18 . The device according to  claim 16 , wherein the convex part is epitaxially grown on the low refractive index layer starting from the low refractive index layer so that the first semiconductor layer is formed as an integrated film. 
     
     
         19 . The device according to  claim 16 , wherein:
 the nitride semiconductor crystal of the low refractive index layer comprises Al with a first composition ratio of Al to Group III elements, and the nitride semiconductor crystal of the first semiconductor layer comprises Al with a second composition ratio of Al to Group III elements lower than the first composition ratio; or   the nitride semiconductor crystal of the low refractive index layer comprises Al, and the nitride semiconductor crystal of the first semiconductor layer does not comprise Al.   
     
     
         20 . A wafer, comprising:
 a substrate;   a semiconductor layer having a first major surface and a second major surface opposite to the first major surface, the first major surface including a first region and a second region, the first region having a rough surface including a convex part and a concave part, and the semiconductor layer made of a nitride semiconductor crystal;   a low refractive index layer in contact with the convex part, the low refractive index layer not covering the concave part, the low refractive index layer made of a nitride semiconductor crystal, and the low refractive index layer having a refractive index lower than the refractive index of the semiconductor layer; and   an electrode provided on the semiconductor layer in the second region.   
     
     
         21 . The wafer according to  claim 20 , wherein a lattice of the low refractive index layer is continuous with a lattice of the semiconductor layer. 
     
     
         22 . The wafer according to  claim 20 , wherein the convex part is epitaxially grown on the low refractive index layer starting from the low refractive index layer so that the semiconductor layer is formed as an integrated film. 
     
     
         23 . The wafer according to  claim 20 , wherein:
 the nitride semiconductor crystal of the low refractive index layer comprises Al with a first composition ratio of Al to Group III elements, and the nitride semiconductor crystal of the semiconductor layer comprises Al with a second composition ratio of Al to Group III elements lower than the first composition ratio; or   the nitride semiconductor crystal of the low refractive index layer comprises Al, and the nitride semiconductor crystal of the semiconductor layer does not comprise Al.   
     
     
         24 . A semiconductor light emitting device, comprising:
 a first semiconductor layer having a first major surface and a second major surface opposite to the first major surface, the first major surface forming a light extraction face, the first major surface having a flat surface, the first major surface including a first region and a second region, and the first semiconductor layer made of a nitride semiconductor crystal;   a light emitting layer having an active layer and provided on the second major surface;   a second semiconductor layer provided on the light emitting layer; and   a low refractive index layer in contact with the first region, the low refractive index layer not covering the second region, the low refractive index layer made of a nitride semiconductor crystal, and the low refractive index layer having a refractive index lower than the refractive index of the first semiconductor layer.   
     
     
         25 . The device according to  claim 24 , wherein a lattice of the low refractive index layer is continuous with a lattice of the first semiconductor layer. 
     
     
         26 . The device according to  claim 24 , wherein the first region is epitaxially grown on the low refractive index layer starting from the low refractive index layer so that the first semiconductor layer is formed as an integrated film. 
     
     
         27 . The device according to  claim 24 , wherein:
 the nitride semiconductor crystal of the low refractive index layer comprises Al with a first composition ratio of Al to Group III elements, and the nitride semiconductor crystal of the first semiconductor layer comprises Al with a second composition ratio of Al to Group III elements lower than the first composition ratio; or   the nitride semiconductor crystal of the low refractive index layer comprises Al, and the nitride semiconductor crystal of the first semiconductor layer does not comprise Al.   
     
     
         28 . The device according to  claim 24 , wherein the low refractive index layer has a pillar shape when viewed in a direction perpendicular to the first major surface. 
     
     
         29 . The device according to  claim 24 , wherein the low refractive index layer has a pyramid shape when viewed in a direction perpendicular to the first major surface. 
     
     
         30 . The device according to  claim 24 , wherein
 a plurality of the low refractive index layers are provided, and   respective width of the plurality of the low refractive index layers are random among the low refractive index layers when viewed in a direction perpendicular to the first major surface.   
     
     
         31 . The device according to  claim 24 , wherein
 a plurality of the low refractive index layers are provided, and   spacing between the plurality of the low refractive index layers are random among the low refractive index layers when viewed in a direction perpendicular to the first major surface.   
     
     
         32 . A wafer, comprising:
 a substrate;   a semiconductor layer having a first major surface and a second major surface opposite to the first major surface, the first major surface having a flat surface, the first major surface including a first region and a second region, and the semiconductor layer made of a nitride semiconductor crystal; and   a low refractive index layer in contact with the first region, the low refractive index layer not covering the second region, the low refractive index layer made of a nitride semiconductor crystal, and the low refractive index layer having a refractive index lower than the refractive index of the semiconductor layer.   
     
     
         33 . The wafer according to  claim 32 , wherein a lattice of the low refractive index layer is continuous with a lattice of the semiconductor layer. 
     
     
         34 . The wafer according to  claim 32 , wherein the first region is epitaxially grown on the low refractive index layer starting from the low refractive index layer so that the semiconductor layer is formed as an integrated film. 
     
     
         35 . The wafer according to  claim 32 , wherein:
 the nitride semiconductor crystal of the low refractive index layer comprises Al with a first composition ratio of Al to Group III elements, and the nitride semiconductor crystal of the semiconductor layer comprises Al with a second composition ratio of Al to Group III elements lower than the first composition ratio; or   the nitride semiconductor crystal of the low refractive index layer comprises Al, and the nitride semiconductor crystal of the semiconductor layer does not comprise Al.