Method for manufacturing optical semiconductor device

A method for manufacturing an optical semiconductor device, comprising:

• a step of sequentially stacking a first conductivity-type cladding layer, an active layer and a second conductivity-type first cladding layer, on a surface of a first conductivity-type semiconductor substrate, and then sequentially stacking further an etching stopper layer and a second conductivity-type second cladding layer, to thereby form semiconductor layers;
• a step of etching the semiconductor layers to form a mesa stripe;
• a step of forming burying layers on both sides of the mesa stripe;
• a step of forming a first conductivity-type blocking layer on a top of the mesa stripe and surfaces of the burying layers;
• a step of forming a mask exposing an area of the first conductivity-type blocking layer corresponding to a central portion of the active layer as viewed from a direction perpendicular to a cross-section of the mesa stripe, and then performing etching up to the etching stopper layer to create an opening;
• a step of removing the mask and the etching stopper layer;
• and
• a step of stacking a second conductivity-type third cladding layer on a surface inside the opening and a surface of the first conductivity-type blocking layer, and then stacking a second conductivity-type contact layer;
• wherein the second conductivity-type first cladding layer has a carrier concentration that is lower than a carrier concentration of the second conductivity-type second cladding layer, and is formed between the second conductivity-type second cladding layer and the active layer and on that active layer;
• and
• wherein a carrier concentration of the second conductivity-type third cladding layer is set to be lower than the carrier concentration of the second conductivity-type second cladding layer.