Semiconductor laser device and method of manufacturing the same

Abstract

A method of manufacturing semiconductor laser device capable of reducing κL, with manufacturing restrictions satisfied, is provided. In a distributed-feedback or distributed-reflective semiconductor laser device, immediately before burying regrowth of a diffraction grating, halogen-based gas is introduced to a reactor, and etching is performed on the diffraction grating so that each side wall has at least two or more crystal faces and a ratio of length of an upper side in a waveguide direction to a bottom side parallel to a (100) surface is 0 to 0.3. And, a reactive product formed on side surfaces of the diffraction grating and in trench portions between stripes of the diffraction grating at an increase of temperature for regrowth is removed. Therefore, the diffraction grating with reduced height and a sine wave shape is obtained, thereby κL of the device is reduced. Thus, an oscillation threshold and optical output efficiency can be improved.

1 . A distributed-feedback or distributed-reflective semiconductor laser device comprising: 
 a diffraction grating formed in stripes perpendicular to a waveguide direction,    wherein the diffraction grating has side walls each having at least two or more crystal faces, and a ratio of length of an upper side in a waveguide direction to a bottom side parallel to a (100) surface is 0 to 0.3.    
     
     
         2 . The semiconductor laser device according to  claim 1 , 
 wherein the diffraction grating is composed of a III-V family compound semiconductor layer including at least one of In, Ga, As, and P elements.    
     
     
         3 . A method of manufacturing semiconductor laser device comprising: 
 a first step of laminating a first clad layer, an active layer, and a diffraction grating layer on a semiconductor substrate through epitaxial growth;    a second step of forming a diffraction grating by etching the diffraction grating layer; and    a third step of performing burying regrowth of the diffraction grating through epitaxial growth on a second clad layer of different conduction type from the first clad layer,    wherein immediately before the third step, halogen-based gas is introduced to a reactor, and etching is performed on the diffraction grating so that each side wall has at least two or more crystal faces and a ratio of length of an upper side in a waveguide direction to a bottom side parallel to a (100) surface is 0 to 0.3, and a reactive product formed on side surfaces of the diffraction grating and in trench portions between stripes of the diffraction grating at an increase in temperature for regrowth is removed.    
     
     
         4 . The method of manufacturing semiconductor laser device according to  claim 3 , 
 wherein in the first step, a first optical guide layer is further formed between the first clad layer and the active layer, and a second optical guide layer and a spacer layer are formed between the active layer and the diffraction grating layer.    
     
     
         5 . The method of manufacturing semiconductor laser device according to  claim 3 , 
 wherein the diffraction grating layer is a III-V family compound semiconductor layer including at least one of In, Ga, As, and P elements.    
     
     
         6 . A method of manufacturing semiconductor laser device comprising: 
 a first step of laminating, through epitaxial growth, a first clad layer and a diffraction grating layer on a semiconductor substrate;    a second step of forming a diffraction grating through etching on the diffraction grating layer; and    a third step of burying the diffraction grating through epitaxial growth on a second clad layer of identical conduction type to the first clad layer for regrowth of the active layer,    wherein immediately before the third step, halogen-based gas is introduced to a reactor, etching is performed on the diffraction grating so that each side wall has at least two or more crystal faces and a ratio of length of an upper side in a waveguide direction to a bottom side parallel to a (100) surface is 0 to 0.3, and a reactive product formed on side surfaces of the diffraction grating and in trench portions between stripes of the diffraction grating at an increase in temperature for regrowth is removed.    
     
     
         7 . The method of manufacturing semiconductor laser device according to  claim 6 , 
 wherein in the third step, a first optical guide layer is further formed between the second clad layer and the active layer, and a second optical guide layer and a third clad layer are formed on an upper portion of the active layer.    
     
     
         8 . The method of manufacturing semiconductor laser device according to  claim 6 , 
 wherein the diffraction grating layer is a III-V family compound semiconductor layer including at least one of In, Ga, As, and P elements.