Nitride semiconductor device

Abstract

The present invention provides a nitride semiconductor light emitting device with an active layer of the multiple quantum well structure, in which the device has an improved luminous intensity and a good electrostatic withstanding voltage, thereby allowing the expanded application to various products. The active layer 7 is formed of a multiple quantum well structure containing In a Ga 1−a N (0≦a<1). The p-cladding layer 8 is formed on said active layer containing the p-type impurity. The p-cladding layer 8 is mode of a multi-film layer including a first nitride semiconductor film containing Al and a second nitride semiconductor film having a composition different from that of said first nitride semiconductor film. Alternatively, the p-cladding layer 8 is made of single-layered layer made of Al b Ga 1−b N (0≦b≦1). A low-doped layer 9 is grown on the p-cladding layer 8 having a p-type impurity concentration lower than that of the p-cladding layer 8. A p-contact layer is grown on the low-doped layer 9 having a p-type impurity concentration higher than those of the p-cladding layer 8 and the low-doped layer 9.

1 . A nitride semiconductor device, comprising: 
 a) a substrate;    b) an active layer of a multiple quantum well structure containing In a Ga 1−a N (0≦a<1)    c) an n-region nitride semiconductor layer structure interposed between said substrate and said active layer;    d) a p-type single-layered formed on said active layer, made of Al b Ga 1−b N (0≦b≦1) containing a p-type impurity;    e) a p-type low-doped layer formed on said p-type single-layered layer, having a concentration of the p-type impurity lower than that of said p-type single-layered layer; and    f) a p-contact layer formed on said p-type low-doped layer, having a concentration of the p-type impurity higher than that of said p-type single-layered layer.    
   
   
       2 . A nitride semiconductor device according to  claim 1 , wherein said p-type low-doped layer is made of Al s Ga 1−s N (0<s<0.5), and said p-type low-doped layer has a composition ratio of Al less than that of said p-type single-layered layer.  
   
   
       3 . A nitride semiconductor device according to  claim 1 , wherein said p-type low-doped layer is made of Al s Ga 1−s N (0<s<0.5), and an average composition ratio of Al of said p-type low-doped layer is less than that of said p-type single-layered layer.  
   
   
       4 . A nitride semiconductor device according to  claim 1 , wherein the impurity contained within said p-type single-layered layer and said p-contact layer is diffused into said p-type low-doped layer.  
   
   
       5 . A nitride semiconductor device according to  claim 1 , wherein the concentration of the p-type impurity of said single-layered layer falls within the range of 5×10 17 /cm 3  through 1×10 21 /cm 3 .  
   
   
       6 . A nitride semiconductor device according to  claim 1 , wherein the concentration of the p-type impurity of said low-doped layer is less than 1×10 21 /cm 3 .  
   
   
       7 . A nitride semiconductor device according to  claim 1 , wherein the concentration of the p-type impurity of said p-contact layer falls within the range of 1×10 18 /cm 3  through 5×10 21 /cm 3 .  
   
   
       8 . A nitride semiconductor device according to  claim 1 , wherein said n-region nitride semiconductor layer structure includes an n-region multi-film layer having a lower-film made of undoped nitride semiconductor, a middle-film doped with an n-type impurity, and an upper-film made of undoped nitride semiconductor.  
   
   
       9 . A nitride semiconductor device according to  claim 1 , wherein said n-region nitride semiconductor layer structure further includes an undoped GaN layer and an n-contact layer containing an n-type impurity, successively formed on said substrate.  
   
   
       10 . A nitride semiconductor device according to  claim 9 , wherein said n-type first multi-film layer is formed on said n-contact layer, and the total thickness of said undoped GaN layer, said n-contact layer, and said n-type first multi-film layer falls within the range of 2 through 20 μm.