Patent ID: 11967617
Assignee: SUMITOMO CHEMICAL COMPANY LIMITED
Field: Semiconductors (Electrical engineering)
Classification: CPC C  H | IPC C  H

Claim 9:
10. A nitride semiconductor substrate comprising a group III nitride semiconductor crystal and having a main surface,
wherein a low index crystal plane nearest to the main surface is (0001) plane curved in a concave spherical shape with respect to the main surface, and
the off-angle (θm, θa) at an arbitrary position (x, y) in the main surface is approximated by the following formula (1):, [
     
      Formula
      ⁢
         
      1
     
     ]
    
   
   
    
   
  
  
   
    
     
      (
      
       
        
         
          θ
          m
         
        
       
       
        
         
          θ
          a
         
        
       
       
        
         1
        
       
      
      )
     
     =
     
      
       (
       
        
         
          
           M
           1
          
         
         
          0
         
         
          
           M
           2
          
         
        
        
         
          0
         
         
          
           A
           1
          
         
         
          
           A
           2
          
         
        
        
         
          0
         
         
          0
         
         
          1
         
        
       
       )
      
      ⁢
      
       (
       
        
         
          x
         
        
        
         
          y
         
        
        
         
          1
         
        
       
       )
      
     
    
   
   
    
     (
     1
     )
    
   
  
 

where x represents a coordinate in a direction along <1-100> axis of the crystal as a position in the main surface, y represents a coordinate in a direction along <11-20> axis of the crystal as a position in the main surface, (0, 0) represents a coordinate (x, y) of the center of the main surface, θm represents a direction component along <1-100> axis in an off-angle of <0001> axis of the crystal with respect to a normal of the main surface, θa represents a direction component along <11-20> axis in the off-angle, (M1, A1) represents a rate of change in the off-angle (θm, θa) with respect to the position (x, y) in the main surface, and (M2, A2) represents the off-angle (θm, θa) at the center of the main surface, and
wherein the off-angle (θm, θa) at least at a part of positions of the main surface satisfies the following formulas (4-1) and (4-2):

−0.05≤θm≤0.21  (4-1)

0.36≤θa≤0.65  (4-2).