Nitride semiconductor laser device and method for fabrication thereof

Abstract

In a nitride semiconductor light-emitting device, and according to a method for fabricating it, a low-defect region having a defect density of 10 6 cm −2 or less and a carved region in the shape of a depressed portion are formed on the surface of a nitride semiconductor substrate, and the etching angle θ, which is the angle between the side surface portion of the depressed portion and an extension line of the bottom surface portion thereof as measured with the depressed portion seen in a sectional view, is in a range of 75°≦θ≦140°. This prevents the development of cracks, and reduces the creep-up growth from the bottom growth portion of the carved region, thereby reducing the film thickness of the side growth portion. This makes it possible to produce, with a high yield, a nitride semiconductor laser device having a nitride semiconductor growth layer with good surface flatness.

1 . A nitride semiconductor light-emitting device comprising: 
 a nitride semiconductor substrate of which at least part of a surface is formed from a nitride semiconductor; and    a nitride film semiconductor growth layer laid on the surface of the nitride semiconductor substrate,    wherein a low-defect region having a defect density of 10 6  cm −2  or less and a carved region in a shape of a depressed portion are formed on the surface of the nitride semiconductor substrate, and    wherein an etching angle θ, which is an angle between a side face portion of the depressed portion and an extension line of a bottom face portion thereof as measured with the depressed portion seen in a sectional view, is in a range of 75°≦θ≦140°.    
     
     
         2 . The nitride semiconductor light-emitting device according to  claim 1 , 
 wherein the etching angle θ is in a range of 85°≦θ≦140°.    
     
     
         3 . The nitride semiconductor light-emitting device according to  claim 1 , 
 wherein, of all layers constituting the nitride film semiconductor growth layer, a layer that makes contact with the surface of the nitride semiconductor substrate is a GaN layer, and this GaN layer is 2 μm or less thick.    
     
     
         4 . The nitride semiconductor light-emitting device according to  claim 1 , 
 wherein, of all layers constituting the nitride film semiconductor growth layer, a layer that makes contact with the surface of the nitride semiconductor substrate is an AlGaN layer.    
     
     
         5 . The nitride semiconductor light-emitting device according to  claim 1 , 
 wherein the carved region is 1 μm or more but 30 μm or less deep.    
     
     
         6 . The nitride semiconductor light-emitting device according to  claim 1 , 
 wherein a laser stripe that is formed in the nitride film semiconductor growth layer so as to function as a light-emitting portion is formed above the low-defect region and elsewhere than above the carved region.    
     
     
         7 . The nitride semiconductor light-emitting device according to  claim 6 , 
 wherein the laser stripe is formed 20 μm or more away from the carved region.    
     
     
         8 . The nitride semiconductor light-emitting device according to  claim 1 , 
 wherein a side growth portion formed, as part of the nitride film semiconductor growth layer, on a side face of the carved region is 20 μm or less thick.    
     
     
         9 . A method for fabricating a nitride semiconductor light-emitting device, the method including a step of forming a nitride film semiconductor growth layer on a surface of a nitride semiconductor substrate of which at least part is formed from a nitride semiconductor and that includes on the surface thereof a low-defect region having a defect density of 10 6  cm −2  or less, the method comprising: 
 a first step of forming a carved region by etching the nitride semiconductor substrate; and    a second step of laying the nitride film semiconductor growth layer on the nitride semiconductor substrate that has undergone the first step,    wherein, in the first step, an etching angle θ, which is an angle between a side face portion of a depressed portion formed as the carved region and an extension line of a bottom face portion of the depressed portion, is in a range of 75°≦θ≦140°.    
     
     
         10 . The method for fabricating a nitride semiconductor light-emitting device according to  claim 9 , 
 wherein, in the first step, the etching angle θ is in a range of 85°≦θ≦140°.    
     
     
         11 . The method for fabricating a nitride semiconductor light-emitting device according to  claim 9 , 
 wherein, in the second step, a layer that makes contact with the surface of the nitride semiconductor substrate is a 2 μm or less thick GaN layer.    
     
     
         12 . The method for fabricating a nitride semiconductor light-emitting device according to  claim 9 , 
 wherein, in the second step, a layer that makes contact with the surface of the nitride semiconductor substrate is an AlGaN layer.    
     
     
         13 . The method for fabricating a nitride semiconductor light-emitting device according to  claim 9 , the method further comprising: 
 a step of forming a laser stripe in the nitride film semiconductor growth layer, above the low-defect region and elsewhere than above the carved region, so as to function as a light-emitting portion.    
     
     
         14 . The method for fabricating a nitride semiconductor light-emitting device according to  claim 13 , 
 wherein the laser stripe is formed 20 μm or more away from the carved region.    
     
     
         15 . The method for fabricating a nitride semiconductor light-emitting device according to  claim 9 , 
 wherein a side growth portion formed, as part of the nitride film semiconductor growth layer, on a side face of the carved region is 20 μm or less thick.    
     
     
         16 . The method for fabricating a nitride semiconductor light-emitting device according to  claim 9 , 
 wherein, in the first step, first a nitride semiconductor layer is grown on the nitride semiconductor substrate, and then the carved region is formed.