Buried type semiconductor optical device and manufacturing method therefor

An optical device comprising:

• a semiconductor substrate that includes a pair of grooves extending in a first direction and includes a convex portion extending in a stripe shape in the first direction between the pair of grooves to constitute a lower end of a mesa stripe structure;
• a quantum well layer that extends in a stripe shape in the first direction on the convex portion so as to constitute a part of the mesa stripe structure;
• a buried layer that is placed on the semiconductor substrate while being adjacent to both sides of the mesa stripe structure in a second direction orthogonal to the first direction so as to constitute a buried heterostructure;
• an electrode that extends continuously from an upper surface of the mesa stripe structure onto the buried layer and contacts the upper surface of the mesa stripe structure;
• and
• a passivation film that is interposed between a part of an upper surface of the buried layer and the electrode
• wherein the upper surface of the buried layer includes:
• a first region that is adjacent to the mesa stripe structure and overlaps with a corresponding one of the pair of grooves,
• a second, flat region that does not overlap with any of the pair of grooves, and
• a connection region that is between the first region and the second, flat region.

A method of manufacturing a buried type semiconductor optical device, the method comprising:

• preparing a semiconductor substrate that includes a pair of grooves extending in a first direction and a convex portion between the pair of grooves and is provided with a mesa stripe structure extending in a stripe shape in the first direction with the convex portion as a lower end portion, in which the mesa stripe structure includes a quantum well layer, a cladding layer, and a contact layer extending in a stripe shape in the first direction on the convex portion;
• forming a buried layer constituting a buried heterostructure by crystal growth so as to be placed on the semiconductor substrate while being adjacent to both sides of the mesa stripe structure in a second direction orthogonal to the first direction;
• forming a passivation film on a second region of an upper surface of the buried layer while avoiding a first region of the upper surface of the buried layer and an upper surface of the mesa stripe structure;
• and
• forming an electrode so as to be in contact with the upper surface of the mesa stripe structure and extend continuously from the upper surface of the mesa stripe structure onto the passivation film, wherein:
• the first region is adjacent to the mesa stripe structure, overlaps with a corresponding one of the pair of grooves, and is inclined so as to be higher in the second direction from the mesa stripe structure,
• the second region does not overlap with any of the pair of grooves, is flat, and is higher than a lower end of the first region, and
• the upper surface of the buried layer further includes a connection region between the first region and the second region at a same height as the second region.