Semiconductor optical integrated device and method of manufacturing semiconductor optical integrated device

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

• forming a modulation layer on a first clad layer of a first conductivity type;
• forming a mask layer in a stripe shape, on the modulation layer;
• etching the modulation layer by using the mask layer as a mask;
• washing a side surface of the etched modulation layer by wet treatment to incline the side surface inward;
• forming a transparent waveguide layer having a lower part connected to the modulation layer, by using the mask layer as a selective growth mask;
• forming an undoped portion between the transparent waveguide layer and the modulation layer on a connection portion between the transparent waveguide layer and the modulation layer;
• removing the mask layer;
• and
• forming a second clad layer of a second conductivity type on the transparent waveguide layer, the modulation layer, and the undoped portion.

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

• forming a transparent waveguide layer on a first clad layer of a first conductivity type;
• forming a mask layer in a stripe shape, on the transparent waveguide layer;
• etching the transparent waveguide layer by using the mask layer as a mask;
• washing a side surface of the etched transparent waveguide layer by wet treatment to incline the side surface inward;
• forming a modulation layer having a lower part connected to the transparent waveguide layer, by using the mask layer as a selective growth mask;
• forming an undoped portion between the transparent waveguide layer and the modulation layer on a connection portion between the transparent waveguide layer and the modulation layer;
• removing the mask layer;
• and
• forming a second clad layer of a second conductivity type on the transparent waveguide layer, the modulation layer, and the undoped portion.