A method for manufacturing an optical semiconductor device having a ridge stripe configuration containing an active layer and current blocking layers which embed both sides of the ridge stripe configuration, comprises steps of forming a mask of an insulating film on a surface of a semiconductor layer containing an active layer, forming a ridge stripe configuration by etching a semiconductor layer using gas containing SiCl.sub.4, removing an oxide layer with regard to a Si based residue which is attached on a surface which is etched of the ridge stripe configuration which is formed and removing a Si based residue whose oxide layer is removed.

A vertical cavity surface emitting laser includes: an active layer including a quantum well structure including one or more well layers including a III-V compound semiconductor containing indium as a group III constituent element; an upper laminated region containing a carbon dopant; and a substrate for mounting a post including the active layer and the upper laminated region, in which the active layer is provided between the upper laminated region and the substrate, the quantum well structure has a carbon concentration of 210.sup.16 cm.sup.3 or less, and the upper laminated region includes a pile-up layer of indium at a position away from the active layer.

A buried semiconductor optical device comprises a semiconductor substrate; a mesa-stripe portion including a multi-quantum well layer on the semiconductor substrate; a buried layer consisting of a first portion and a second portion, the first portion covering one side of the mesa-stripe portion, the second portion covering the other side of the mesa-stripe portion, and the first portion and the second portion covering a surface of the semiconductor substrate; and an electrode configured to cause an electric current to flow through the mesa-stripe portion, the buried layer comprising, from the surface of the semiconductor substrate, a first sublayer, a second sublayer, and a third sublayer, the first sublayer, the second sublayer, and the third sublayer each consisting of semi-insulating InP, the first sublayer and the second sublayer forming a pair structure, the second sublayer being located above the multi-quantum well layer from the surface of the semiconductor substrate, and the second sublayer consisting of one or more layers selected from a group of InGaAs, InAAs, InGaAAs, InGaAsP, and InAlAsP.

A distributed feedback laser, including: a ridge waveguide; two upper electrodes disposed on two sides of the ridge waveguide, respectively; two lower electrodes disposed on two sides of the upper electrodes, respectively; a substrate; a second waveguide cladding layer; an active layer; and a first waveguide cladding layer. The first waveguide cladding layer is n-doped and includes a conductive layer and a refractive layer disposed on the conductive layer. The refractive index of the refractive layer is greater than the refractive index of the active layer. The ridge waveguide includes a ridge region formed by a middle part of the refractive layer. The ridge region includes a surface provided with Bragg gratings. Two grooves are formed between the ridge waveguide and the upper electrodes. The conductive layer is connected to the upper electrodes. The second waveguide cladding layer includes one or more current restricted areas.

A surface emitting laser includes a conductive substrate, a metal bonding layer, a laser structure layer, an epitaxial semiconductor reflection layer, and an electrode layer. The laser structure layer has an epitaxial current-blocking layer having a current opening. Currents are transmitting through the current opening. The epitaxial current-blocking layer is grown by a semiconductor epitaxy process to confine the range of the currents to form electric fields.

A semiconductor optical integrated device according to the present invention includes a conductive substrate, a laser provided to the conductive substrate, a semi-insulating semiconductor layer provided on the conductive substrate, a photodiode provided on the semi-insulating semiconductor layer and a waveguide that is provided on the conductive substrate and guides output light of the laser to the photodiode, wherein an anode of the photodiode and a cathode of the photodiode are drawn from an upper surface side of the photodiode, and the waveguide and the photodiode are separated from each other by the semi-insulating semiconductor layer.

A vertical cavity surface emitting laser includes: an active layer including a quantum well structure including one or more well layers including a III-V compound semiconductor containing indium as a group III constituent element; an upper laminated region containing a carbon dopant; and a substrate for mounting a post including the active layer and the upper laminated region, in which the active layer is provided between the upper laminated region and the substrate, the quantum well structure has a carbon concentration of 210.sup.16 cm.sup.3 or less, and the upper laminated region includes a pile-up layer of indium at a position away from the active layer.

A vertical cavity surface emitting laser includes an active layer having a quantum well structure, a first laminate for a first distributed Bragg reflector, and a first spacer region provided between the active layer and the first laminate. A barrier layer of the quantum well structure includes a first compound semiconductor containing aluminum as a group m constituent element. The first spacer region includes a second compound semiconductor having a larger aluminum composition than the first compound semiconductor. A concentration of first dopant in the first laminate is larger than a concentration of the first dopant in the first portion of the first spacer region. The concentration of the first dopant in the first portion of the first spacer region is larger than a concentration of the first dopant in the second portion of the first spacer region.

A semiconductor light-emitting element includes a laminated structure which has an active layer between a first conductivity-type semiconductor layer and a second conductivity-type semiconductor layer, a first semiconductor layer which includes at least the first conductivity-type semiconductor layer of the laminated structure, an insulation film which is formed on the first semiconductor layer and has an opening, and a second semiconductor layer which is formed on the insulation film and includes at least the second conductivity-type semiconductor layer of the laminated structure. The second semiconductor layer includes a first region facing the opening of the insulation film and a second region not facing the opening, and the second region has a portion with a higher impurity concentration than the first region.

A semiconductor laser device lases in a multiple transverse mode and includes a stacked structure where a first conductivity-side semiconductor layer, an active layer, and a second conductivity-side semiconductor layer are stacked above a substrate. The second conductivity-side semiconductor layer includes a current block layer having an opening that delimits a current injection region. Side faces as a pair are formed in portions of the stacked structure that range from part of the first conductivity-side semiconductor layer to the second conductivity-side semiconductor layer. The active layer has a second width greater than a first width of the opening. The side faces in at least part of the first conductivity-side semiconductor layer are inclined to the substrate. A maximum intensity position in a light distribution of light guided in the stacked structure, in a direction of the normal to the substrate, is within the first conductivity-side semiconductor layer.