Semiconductor device and semiconductor device manufacturing method

Abstract

A technique is provided which enables formation of nitride semiconductor layers with excellent flatness and excellent crystallinity on a gallium nitride substrate (GaN substrate), while improving the producibility of the semiconductor device using the GaN substrate. A gallium nitride substrate is prepared which has an upper surface having an off-angle of not less than 0.1° nor more than 1.0° in a <1-100> direction, with respect to a (0001) plane. Then, a plurality of nitride semiconductor layers including an n-type semiconductor layer are stacked on the upper surface of the gallium nitride substrate to form a semiconductor device such as a semiconductor laser.

1 . A semiconductor device comprising: 
 a gallium nitride substrate; and    a nitride semiconductor layer that is formed on an upper surface of said gallium nitride substrate,    wherein said upper surface of said gallium nitride substrate has an off-angle of not less than 0.1° nor more than 1.0° in a <1-100> direction with respect to a (0001) plane.    
     
     
         2 . The semiconductor device according to  claim 1 , wherein said off-angle is set to be not less than 0.25° nor more than 1.0°.  
     
     
         3 . The semiconductor device according to  claim 2 , wherein said off-angle is set to be not less than 0.3° nor more than 1.0°.  
     
     
         4 . The semiconductor device according to  claim 2 , wherein said upper surface of said gallium nitride substrate has an off-angle of not less than 0° nor more than 0.1° in a <11-20> direction with respect to the (0001) plane.  
     
     
         5 . The semiconductor device according to  claim 1 , wherein said nitride semiconductor layer is an n-type semiconductor layer having an impurity concentration of not less than 1×10 16  cm −3  nor more than 1×10 20  cm −3 .  
     
     
         6 . The semiconductor device according to  claim 5 , wherein said nitride semiconductor layer is an n-type semiconductor layer having an impurity concentration of not less than 1×10 17  cm −3  nor more than 1×10 19  cm −3 .  
     
     
         7 . The semiconductor device according to  claim 6 , wherein said nitride semiconductor layer is an n-type semiconductor layer having an impurity concentration of not less than 1×10 17  cm −3  nor more than 5×10 18  cm −3 .  
     
     
         8 . A semiconductor device manufacturing method comprising the steps of: 
 (a) preparing a gallium nitride substrate whose upper surface has an off-angle of not less than 0.1° nor more than 1.0° in a <1-100> direction with respect to a (0001) plane; and    (b) forming a nitride semiconductor layer on said upper surface of said gallium nitride substrate.    
     
     
         9 . The semiconductor device manufacturing method according to  claim 8 , further comprising the step (c) of, between said steps (a) and (b), applying a thermal process to said gallium nitride substrate for 5 minutes or longer at not less than 800° C. nor more than 1200° C. in an atmosphere of a gas at least containing NH 3  or a gas at least containing NH 3  and H 2 , 
 wherein, when the gas at least containing NH 3  and H 2  is used in said step (c), a percentage of H 2  in the gas is set at 30% or less.    
     
     
         10 . The semiconductor device manufacturing method according to  claim 9 , wherein, in said step (c), the thermal process is applied to said gallium nitride substrate for not less than 5 minutes nor more than 30 minutes.  
     
     
         11 . The semiconductor device manufacturing method according to  claim 9 , wherein, in said step (c), the thermal process is applied to said gallium nitride substrate at not less than 1000° C. nor more than 1200° C.  
     
     
         12 . The semiconductor device manufacturing method according to  claim 9 , wherein, in said step (c), the thermal process is applied to said gallium nitride substrate at 1000° C. for 10 minutes or more, and when the gas at least containing NH 3  and H 2  is used, a percentage of H 2  in the gas is set at 10% or less.