Nitride Semiconductor Device And Production Method Thereof

Abstract

A nitride semiconductor device according to the present invention includes a p-type nitride semiconductor layer, an n-type nitride semiconductor layer, and an active layer interposed between the p-type nitride semiconductor layer and the n-type nitride semiconductor layer. The p-type nitride semiconductor layer includes: a first p-type nitride semiconductor layer containing Al and Mg; and a second p-type nitride semiconductor layer containing Mg. The first p-type nitride semiconductor layer is located between the active layer and the second p-type nitride semiconductor layer, and the second p-type nitride semiconductor layer has a greater band gap than a band gap of the first p-type nitride semiconductor layer.

1 . A nitride semiconductor device comprising a p-type nitride semiconductor layer, an n-type nitride semiconductor layer, and an active layer interposed between the p-type nitride semiconductor layer and the n-type nitride semiconductor layer, wherein, 
 the p-type nitride semiconductor layer includes: 
 a first p-type nitride semiconductor layer containing Al and Mg; and  
 a second p-type nitride semiconductor layer containing Mg,  
   the first p-type nitride semiconductor layer being located between the active layer and the second p-type nitride semiconductor layer, and    the second p-type nitride semiconductor layer having a greater band gap than a band gap of the first p-type nitride semiconductor layer.    
     
     
         2 . The nitride semiconductor device of  claim 1 , wherein the second p-type nitride semiconductor layer functions as a barrier layer for suppressing a carrier overflow from the active layer.  
     
     
         3 . The nitride semiconductor device of  claim 1 , wherein, 
 the first p-type nitride semiconductor layer has an Al concentration of no less than 1×10 20  cm −3  and no more than 2×10 21  cm −3 ; and    a region of the first p-type nitride semiconductor layer in which the Al concentration is no less than 1×10 20  cm −3  and no more than 2×10 21  cm −3  has a thickness of 1 nm or more.    
     
     
         4 . The nitride semiconductor device of  claim 1 , further comprising a non-doped nitride semiconductor layer which contains Al and which is located between the first p-type nitride semiconductor layer and the active layer.  
     
     
         5 . The nitride semiconductor device of  claim 4 , wherein the non-doped nitride semiconductor layer has a smaller band gap than a band gap of the second p-type nitride semiconductor layer.  
     
     
         6 . The nitride semiconductor device of  claim 5 , wherein the non-doped nitride semiconductor layer has a band gap equal to the band gap of the first p-type nitride semiconductor layer.  
     
     
         7 . The nitride semiconductor device of  claim 4 , wherein a total thickness of the non-doped nitride semiconductor layer and the first p-type nitride semiconductor layer is no less than 1 nm and no more than 50 nm.  
     
     
         8 . The nitride semiconductor device of  claim 7 , wherein the second p-type nitride semiconductor layer has a thickness of no less than 5 nm and no more than 20 nm.  
     
     
         9 . The nitride semiconductor device of  claim 8 , wherein a region of the second p-type nitride semiconductor layer which has an Mg concentration of 8×10 18  cm −3  or less has a thickness of 1 nm or less.  
     
     
         10 . The nitride semiconductor device of  claim 1 , wherein, 
 the p-type nitride semiconductor layer further includes a third p-type nitride semiconductor layer having a smaller band gap than a band gap of the second p-type nitride semiconductor layer; and    the second p-type nitride semiconductor layer is located between the third p-type nitride semiconductor layer and the first p-type nitride semiconductor layer.    
     
     
         11 . The nitride semiconductor device of  claim 10 , wherein the third p-type nitride semiconductor layer has a smaller band gap than the band gap of the first p-type nitride semiconductor layer.  
     
     
         12 . The nitride semiconductor device of  claim 10 , wherein the third p-type nitride semiconductor layer functions as a cladding layer.  
     
     
         13 . The nitride semiconductor device of  claim 10 , wherein at least one of the first p-type nitride semiconductor layer and the second p-type nitride semiconductor layer contains In.  
     
     
         14 . The nitride semiconductor device of  claim 13 , wherein the second p-type nitride semiconductor layer has a greater In mole fraction than an In mole fraction of the first p-type nitride semiconductor layer.  
     
     
         15 . A production method for a nitride semiconductor device including a p-type nitride semiconductor layer, an n-type nitride semiconductor layer, and an active layer interposed between the p-type nitride semiconductor layer and the n-type nitride semiconductor layer, wherein: the p-type nitride semiconductor layer includes a first p-type nitride semiconductor layer containing Al and Mg and a second p-type nitride semiconductor layer containing Mg; the first p-type nitride semiconductor layer is located between the active layer and the second p-type nitride semiconductor layer; and the second p-type nitride semiconductor layer has a greater band gap than a band gap of the first p-type nitride semiconductor layer, the production method comprising: 
 a step of forming the n-type nitride semiconductor layer;    a step of forming the active layer;    a step of forming the first p-type nitride semiconductor layer containing Al and Mg by supplying both a source gas having Mg and a source gas having Al; and    a step of forming the second p-type nitride semiconductor layer by supplying a source gas having Mg.    
     
     
         16 . The production method of  claim 15 , further comprising, before the step of forming the first p-type nitride semiconductor layer, a step of forming a non-doped nitride semiconductor layer which contains Al by supplying a source gas having Al without supplying any p-type impurities.  
     
     
         17 . The production method of  claim 15 , wherein, 
 the first p-type nitride semiconductor layer has an Al concentration of no less than 1×10 20  cm −3  and no more than 2×10 21  cm −3 ; and    a region of the first p-type nitride semiconductor layer in which the Al concentration is no less than 1×10 20  cm −3  and no more than 2×10 21  cm −3  has a thickness of 1 nm or more.