Monolithic integrated semiconductor device of semiconductor laser and optical waveguide

DETAILED DESCRIPTION It is hence a primary object of this invention to present a semiconductor device in a construction wherein the active layer and optical waveguide are coupled together at high efficiency without causing axial deviation of the film thickness deviation.
It is another object of this invention to present a method of easily fabricating a semiconductor device in a construction wherein the active layer and optical waveguide are coupled together at high efficiency.
These and other objects are accomplished by a semiconductor device according to the invention, of which semiconductor device includes a semiconductor substrate, an active layer of a quantum well structure disposed on said semiconductor substrate, an optical waveguide formed by disordering part of said active layer, and a clad layer disposed on said active layer and optical waveguide.
In a first illustrative embodiment, disordering is effected by doping of impurities at high concentration or by local annealing.
In a second illustrative embodiment, a semiconductor layer is formed on said semiconductor substrate, and the active layer is formed on this semiconductor layer.
In a third illustrative embodiment, a grating is formed at least in the portion corresponding to said optical waveguide on the surface of said semiconductor layer.
In a fourth illustrative embodiment, a grating may be also formed at least in a portion other than the area corresponding to said optical waveguide on the surface of said semiconductor layer.
In a fifth illustrative embodiment, a reflection layer to feed back the output light from the active layer to the active layer is provided at a different end of the optical waveguide from the end contacting with the active layer.
In a sixth illustrative embodiment, said reflection layer is a multilayer structure of dielectric layers, or a multilayer structure of dielectric layers and metal layers.
In a seventh illustrative embodiment, said active layer is an active layer of a distributed feedback type laser or a distributed reflection type laser