Semiconductor optical device and method of manufacturing the same

An integrated light source comprising:

• a semiconductor laser placed on a semiconductor substrate having a first crystallographic orientation;
• and
• an optical modulator placed adjacent to said semiconductor laser on the same semiconductor substrate,
• wherein said semiconductor laser and said optical modulator comprise
• a multilayer structure constituted by at least a cladding layer having an n-type conductivity, an active region, and a cladding layer having a p-type conductivity which are successively formed on a semiconductor substrate having a first crystallographic orientation, and
• buried layers which are made of a ruthenium-doped semi-insulating semiconductor crystal and formed on two sides of the mesa-stripe-like multilayer structure, and
• an electrically activated ruthenium concentration in the ruthenium-doped semi-insulating semiconductor crystal grown on the growth surface having the second crystallographic orientation which is formed in the process of growing the semi-insulating semiconductor crystal is substantially equal to or higher than an electrically activated ruthenium concentration in the ruthenium-doped semi-insulating semiconductor crystal grown on the growth surface having first crystallographic orientation, and
• the second crystallographic orientation is different from the first crystallographic orientation.

A method of manufacturing a semiconductor optical device comprising:

• the step of forming, on a semiconductor substrate having a first crystallographic orientation, a multilayer structure constituted by a cladding layer having an n-type conductivity, an active region formed from an active layer or a photoabsorption layer, and a cladding layer having a p-type conductivity;
• the step of processing the multilayer structure into a mesa stripe;
• and
• the step of burying two sides of the mesa-stripe-like multilayer structure in a ruthenium-doped semi-insulating semiconductor crystal,
• wherein an electrically activated ruthenium concentration in the ruthenium-doped semi-insulating semiconductor crystal grown on the growth surface having the second crystallographic orientation is substantially equal to or higher than an electrically activated ruthenium concentration in the ruthenium-doped semi-insulating semiconductor crystal grown on the growth surface having the first crystallographic orientation, and
• the second crystallographic orientation is different from the first crystallographic orientation.