Nitride semiconductor device and method for manufacturing the same

Abstract

A nitride semiconductor device includes: a substrate having a principal surface; a first nitride semiconductor layer formed on the principal surface of the substrate and includes one or more convex portions whose side surfaces are vertical to the principal surface; and a second nitride semiconductor layer selectively grown on the side surfaces of the one or more convex portions of the first nitride semiconductor layer.

1 . A nitride semiconductor device comprising:
 a substrate having a principal surface;   a first nitride semiconductor layer formed on the principal surface of the substrate and includes one or more convex portions whose side surfaces are vertical to the principal surface; and   a second nitride semiconductor layer selectively grown on the side surfaces of the one or more convex portions of the first nitride semiconductor layer.   
     
     
         2 . The nitride semiconductor device of  claim 1 , wherein
 the side surfaces of the one or more convex portions are provided by forming protrusions and depressions in at least a top portion of the first nitride semiconductor layer,   the first and second nitride semiconductor layers have a p-type conductivity and   the second nitride semiconductor layer has a higher p-type carrier concentration than the first nitride semiconductor layer.   
     
     
         3 . The nitride semiconductor device of  claim 1 , wherein
 the side surfaces of the one or more convex portions are provided by forming protrusions and depressions in at least a top portion of the first nitride semiconductor layer,   the first and second nitride semiconductor layers have a p-type conductivity and   the second nitride semiconductor layer has a lower residual hydrogen concentration than the first nitride semiconductor layer.   
     
     
         4 . The nitride semiconductor device of  claim 1 , wherein
 the side surfaces of the one or more convex portions are provided by forming protrusions and depressions in at least a top portion of the first nitride semiconductor layer,   the first and second nitride semiconductor layers have a p-type conductivity and   the composition of the first nitride semiconductor layer is Al x Ga 1-x N (wherein 0≦x≦1) and the composition of the second nitride semiconductor layer is Al x Ga 1-x N y P z As 1-y-z  (wherein 0≦x, y, z≦1 and 0<y+z<1).   
     
     
         5 . The nitride semiconductor device of  claim 1 , wherein
 the side surfaces of the one or more convex portions are provided by forming protrusions and depressions in at least a top portion of the first nitride semiconductor layer,   the first and second nitride semiconductor layers have a p-type conductivity and   the second nitride semiconductor layer has a higher refractive index than the first nitride semiconductor layer.   
     
     
         6 . The nitride semiconductor device of  claim 2  further comprising:
 an electrode formed on the second nitride semiconductor layer in contact with the second nitride semiconductor layer, wherein   the second nitride semiconductor layer is formed to bury the protrusions and depressions.   
     
     
         7 . The nitride semiconductor device of  claim 2 , wherein
 the protrusions and depressions provide a photonic crystal structure.   
     
     
         8 . The nitride semiconductor device of  claim 2 , wherein
 the first and second nitride semiconductor layers are configured to form a ridge stripe extending in a certain direction.   
     
     
         9 . The nitride semiconductor device of  claim 8 , wherein
 the protrusions and depressions extend in a direction vertical to the certain direction and are arranged periodically along the certain direction.   
     
     
         10 . The nitride semiconductor device of  claim 1 , wherein
 the side surfaces of the one or more convex portions of the first nitride semiconductor layer have a (000-1), (11-20) or (1-100) plane orientation.   
     
     
         11 . The nitride semiconductor device of  claim 1 , wherein
 the first nitride semiconductor layer has a first conductivity type and includes a ridge stripe extending in a certain direction,   the second nitride semiconductor layer is an overhanging semiconductor layer which is grown on the side surfaces of the ridge stripe of the first nitride semiconductor layer in a direction parallel to the principal surface of the substrate and   the nitride semiconductor device further includes a third nitride semiconductor layer formed to cover the top surfaces of the ridge stripe and the overhanging semiconductor layer and includes an active layer.   
     
     
         12 . The nitride semiconductor device of  claim 11 , wherein
 the overhanging semiconductor layer is insulative or has a second conductivity type.   
     
     
         13 . The nitride semiconductor device of  claim 11 , wherein
 part of the overhanging semiconductor layer has a larger band gap than the first nitride semiconductor layer.   
     
     
         14 . The nitride semiconductor device of  claim 11 , wherein
 the composition of the overhanging semiconductor layer is varied periodically in a direction away from the side surfaces of the ridge stripe of the first nitride semiconductor layer.   
     
     
         15 . The nitride semiconductor device of  claim 11 , wherein
 the composition of the overhanging nitride semiconductor layer is varied continuously in a direction away from the side surfaces of the ridge stripe of the first nitride semiconductor layer such that the band gap of the overhanging semiconductor layer is continuously increased.   
     
     
         16 . The nitride semiconductor device of  claim 11 , wherein
 a gap is formed between parts of the first nitride semiconductor layer on the sides of the ridge stripe and the overhanging semiconductor layer.   
     
     
         17 . The nitride semiconductor device of  claim 11 , wherein
 the top surface of the ridge stripe of the first nitride semiconductor layer has a (0001) plane orientation.   
     
     
         18 . The nitride semiconductor device of  claim 11 , wherein
 the top surface of the ridge stripe of the first nitride semiconductor layer has periodic protrusions and depressions.   
     
     
         19 . The nitride semiconductor device of  claim 11 , wherein
 the width of the ridge stripe of the first nitride semiconductor layer is varied continuously along the certain direction.   
     
     
         20 . The nitride semiconductor device of  claim 11 , wherein
 the width of the ridge stripe of the first nitride semiconductor layer is varied periodically along the certain direction.   
     
     
         21 . The nitride semiconductor device of  claim 11 , wherein
 part of the first nitride semiconductor layer and the other part of the first nitride semiconductor layer aligned along the direction vertical to the principal surface of the substrate have compositions different from each other.   
     
     
         22 . The nitride semiconductor device of  claim 11 , wherein
 the side surfaces of the ridge stripe of the first nitride semiconductor layer have at least a single plane orientation.   
     
     
         23 . The nitride semiconductor device of  claim 11 , wherein
 the top surface of the ridge stripe of the first nitride semiconductor layer is lower than the top surface of the overhanging semiconductor layer.   
     
     
         24 . The nitride semiconductor device of  claim 11 , wherein
 part of the active layer located above the ridge stripe has a longer adsorption edge wavelength than part of the active layer located above the overhanging semiconductor layer.   
     
     
         25 . The nitride semiconductor device of  claim 11 , wherein
 the overhanging semiconductor layer has a lower residual hydrogen concentration than the first nitride semiconductor layer.   
     
     
         26 . The nitride semiconductor device of  claim 1 , wherein
 the second nitride semiconductor layer is formed using an organic nitride material as a nitrogen source.   
     
     
         27 . The nitride semiconductor device of  claim 26 , wherein
 the organic nitride material contains asymmetric dimethylhydrazine or asymmetric dibutylhydrazine as a main ingredient.   
     
     
         28 . A method for manufacturing a nitride semiconductor device comprising the steps of:
 forming a first nitride semiconductor layer on a substrate;   forming one or more convex portions in at least a top portion of the first nitride semiconductor layer; and   selectively growing a second nitride semiconductor layer on the side surfaces of the one or more convex portions of the nitride semiconductor layer using an organic nitride material as a nitrogen source after the step of forming the one or more convex portions.   
     
     
         29 . The method of  claim 28 , wherein
 the side surfaces of the one or more convex portions of the first nitride semiconductor layer have a (000-1), (11-20) or (1-100) plane orientation.   
     
     
         30 . The method of  claim 28 , wherein
 the first and second nitride semiconductor layers have a p-type conductivity and   at least one of phosphorus and arsenic is added to the second nitride semiconductor layer during the step of forming the second nitride semiconductor layer.   
     
     
         31 . The method of  claim 30 , wherein
 an organic phosphorus material is used as a phosphorus source and an organic arsenic material is used as an arsenic source in the step of forming the second nitride semiconductor layer.   
     
     
         32 . The method of  claim 28 , wherein
 the organic nitride material is asymmetric dimethylhydrazine or asymmetric dibutylhydrazine.   
     
     
         33 . A method for manufacturing a nitride semiconductor device comprising the steps of:
 forming on a substrate a first nitride semiconductor layer whose principal surface has a (000-1), (11-20) or (1-100) plane orientation and   growing a second nitride semiconductor layer on the first nitride semiconductor layer using an organic nitride material as a nitrogen source after the step of forming the first nitride semiconductor layer.   
     
     
         34 . The method of  claim 33 , wherein
 the first and second nitride semiconductor layers have a p-type conductivity and   at least one of phosphorus and arsenic is added to the second nitride semiconductor layer in the step of forming the second nitride semiconductor layer.   
     
     
         35 . The method of  claim 34 , wherein
 an organic phosphorus material is used as a phosphorus source and an organic arsenic material is used as an arsenic source in the step of forming the second nitride semiconductor layer.   
     
     
         36 . The method of  claim 33 , wherein
 the organic nitride material is asymmetric dimethylhydrazine or asymmetric dibutylhydrazine.