Semiconductor device for control of a signal light

Claim 1

A semiconductor device for control of a signal light, said device comprising: a first semiconductor cladding layer on a semiconductor substrate; a semiconductor layer including an InGaAsP mixed crystal for functioning as one selected from a guiding layer, an absorption layer, and an active layer; said semiconductor layer including said InGaAsP mixed crystal and said one selected layer being of said InGaAsP mixed crystal having a wavelength composition of 1.45 μm; a second semiconductor cladding layer on said semiconductor layer including said InGaAsP mixed crystal; said first and second semiconductor cladding layers being said InGaAsP mixed crystal having a wavelength composition of 1.5 μm; a third semiconductor cladding layer on said second semiconductor cladding layer; a semiconductor cap layer on said third semiconductor cladding layer; and means for applying an electric field to said semiconductor layer including said InGaAsP mixed crystal; wherein at least said semiconductor cap layer and said third cladding layer are shaped to provide a ridge type waveguide in cooperation with said first and second semiconductor cladding layers and said semiconductor layer including said InGaAsP crystal layer; and at least one of said first to third semiconductor cladding layers includes an InGaAsP mixed crystal having a bandgap energy which is larger than said InGaAsP mixed crystal included in said semiconductor layer of said one selected; and said ridge type waveguide is formed by selective crystal growth, so that side planes of ridge thereof is an (111) plane.