Light-emitting device and manufacturing method thereof

Abstract

A light-emitting device including a substrate; a first conductivity semiconductor layer on the substrate; a first barrier on the first conductivity semiconductor layer; a well on the first barrier and including a first region having a first energy gap and a second region having a second energy gap and closer to the semiconductor layer than the first region; a second barrier on the well; and a second conductivity semiconductor layer on the second barrier; wherein the first energy gap decreases along a stacking direction of the light-emitting device and has a first gradient, the second energy gap increases along the stacking direction and has a second gradient, and an absolute value of the first gradient is smaller than an absolute value of the second gradient.

What is claimed is: 
     
         1 . A light-emitting device comprising:
 a first conductivity semiconductor layer;   a first barrier on the first conductivity semiconductor layer;   a well on the first barrier and comprising:
 a first region having a first energy gap; and 
 a second region having a second energy gap, wherein the first region is closer to the first conductivity semiconductor layer than the second region is; 
   a second barrier on the well; and   a second conductivity semiconductor layer on the second barrier;   wherein the first energy gap is decreased along a stacking direction of the light-emitting device and has a first gradient, the second energy gap is increased along the stacking direction and has a second gradient, and an absolute value of the first gradient is smaller than an absolute value of the second gradient.   
     
     
         2 . The light-emitting device of  claim 1 , wherein the first energy gap and/or the second energy gap are/is varied linearly or stepwise. 
     
     
         3 . The light-emitting device of  claim 1 , wherein the well further comprises a third region between the first region and the second region, and the third region has a third energy gap which is a constant or devoid of gradient variation. 
     
     
         4 . The light-emitting device of  claim 3 , wherein a material of the first barrier and the second barrier comprises gallium nitride, a material of the well comprises indium gallium nitride, and an energy gap of the first barrier and an energy gap of the second barrier are greater than an energy gap of the well. 
     
     
         5 . The light-emitting device of  claim 4 , wherein an indium content of the first region is increased along the stacking direction, an indium content of the second region is decreased along the stacking direction, and an indium content of the third region is a constant. 
     
     
         6 . The light-emitting device of  claim 4 , wherein the indium content of the first region and/or the indium content of the second region are/is varied linearly or stepwise. 
     
     
         7 . The light-emitting device of  claim 3 , wherein a material of the first barrier and the second barrier comprises aluminum nitride, a material of the well comprises aluminum gallium nitride, an aluminum content of the first region is decreased along the stacking direction, an aluminum content of the second region is increased along the stacking direction, and an aluminum content of the third region is substantially a constant. 
     
     
         8 . The light-emitting device of  claim 1 , further comprising a substrate under the first conductivity semiconductor layer, and a buffer layer between the first conductivity semiconductor layer and the substrate. 
     
     
         9 . The light-emitting device of  claim 1 , further comprising a strain releasing stack, wherein the strain releasing stack is on the first conductivity semiconductor layer and comprises a superlattice structure. 
     
     
         10 . The light-emitting device of  claim 9 , wherein the superlattice structure comprises alternately stacking indium gallium nitride layers and gallium nitride layers. 
     
     
         11 . A light-emitting device comprising:
 a first conductivity semiconductor layer;   a first barrier on the first conductivity semiconductor layer;   a well on the first barrier and comprising:
 a first region having a first energy gap; and 
 a second region having a second energy gap, wherein the first region is closer to the first conductivity semiconductor layer than the second region is; 
   a second barrier on the well; and   a second conductivity semiconductor layer on the second barrier;   wherein the first energy gap is decreased along a stacking direction of the light-emitting device and has a first gradient, the second energy gap is increased along the stacking direction and has a second gradient, and an absolute value of the first gradient is greater than an absolute value of the second gradient.   
     
     
         12 . The light-emitting device of  claim 11 , wherein the first energy gap and the second energy gap is varied linearly or stepwise. 
     
     
         13 . The light-emitting device of  claim 11 , wherein the well further comprises a third region between the first region and the second region, and the third region has a third energy gap which is a constant or devoid of gradient variation. 
     
     
         14 . The light-emitting device of  claim 13 , wherein a material of the first barrier and the second barrier comprises gallium nitride, a material of the well comprises indium gallium nitride, and an energy gap of the first barrier and an energy gap of the second barrier are greater than an energy gap of the well. 
     
     
         15 . The light-emitting device of  claim 14 , wherein an indium content of the first region is increased along the stacking direction, an indium content of the second region is decreased along the stacking direction, and an indium content of the third region is a constant. 
     
     
         16 . The light-emitting device of  claim 14 , wherein the indium content of the first region and/or the indium content of the second region are/is varied linearly or stepwise. 
     
     
         17 . The light-emitting device of  claim 13 , wherein a material of the first barrier and the second barrier comprises aluminum nitride, a material of the well comprises aluminum gallium nitride, an aluminum content of the first region is decreased along the stacking direction, an aluminum content of the second region is increased along the stacking direction, and an aluminum content of the third region is substantially a constant. 
     
     
         18 . The light-emitting device of  claim 11 , further comprising a substrate under the first conductivity semiconductor layer, and a buffer layer between the first conductivity semiconductor layer and the substrate. 
     
     
         19 . The light-emitting device of  claim 11 , further comprising a strain releasing stack, wherein the strain releasing stack is on the first conductivity semiconductor layer and comprises a superlattice structure. 
     
     
         20 . The light-emitting device of  claim 19 , wherein the superlattice structure comprises alternately stacking indium gallium nitride layers and gallium nitride layers.