Provided here are: a mesa strip which has an n-type cladding layer, an active layer and a p-type cladding layer that are stacked sequentially on a surface of an n-type substrate; Fe-doped semi-insulating layers which are embedded along both sides of the mesa stripe, each up to a height higher than the mesa stripe; n-type blocking layers which are stacked on respective surfaces of the Fe-doped semi-insulating layers located on the both sides of the mesa stripe, and which are spaced apart from each other with an interval that is a space corresponding to a central portion of the active layer and is thus narrower than the active layer; p-type cladding layers which are formed on back surfaces of respective mesa-stripe-side end portions of the n-type blocking layers; and a p-type cladding layer which buries a top of the mesa stripe, the p-type cladding layers and the n-type blocking layers.

A method of fabricating a gain medium includes growing a p-type layer doped with zinc on a substrate, growing an undoped layer including one or both of InP or InGaAsP on the p-type layer, growing a region that includes multiple quantum wells (MQWs) on the undoped layer, and growing an n-type layer on the region. The undoped layer has a thickness that is sufficient to prevent Zn diffusion from the p-type layer into the region during subsequent growth or wafer fabrication steps.

A light-emitting device includes an insulating base member having thermal conductivity of 10 W/m.Math.K or more; a light-emitting element that has a cathode electrode and an anode electrode and is provided on a front surface side of the base member; a capacitive element that is provided on the base member and supplies an electric current to the light-emitting element; and a reference potential wire that is provided on a rear surface side of the base member and is connected to an external reference potential. The reference potential wire is connected to the capacitive element and is insulated from the cathode electrode and the anode electrode.

A semiconductor device according to the present application includes a semiconductor substrate, an n-type first cladding layer provided on the semiconductor substrate, an n-type second cladding layer provided on the first cladding layer, an active layer provided on the second cladding layer, a p-type third cladding layer provided on the active layer, a surface electrode provided above the third cladding layer, a back surface electrode provided below the semiconductor substrate and a p-type diffusion prevention layer provided between the first cladding layer and the second cladding layer.

An AlGaInPAs-based semiconductor laser device includes a substrate, an n-type clad layer, an n-type guide layer, an active layer, a p-type guide layer composed of AlGaInP containing Mg as a dopant, a p-type clad layer composed of AlInP containing Mg as a dopant, and a p-type cap layer composed of GaAs. Further, the semiconductor laser device has, between the p-type guide layer and the p-type clad layer, a Mg-atomic concentration peak which suppresses inflow of electrons, moving from the n-type clad layer to the active layer, into the p-type guide layer or the p-type clad layer.

A semiconductor optical element includes: a first conductivity type semiconductor substrate; and a laminated body disposed on the first conductivity type semiconductor substrate. The laminated body includes, in the following order from a side of the first conductivity type semiconductor substrate: a first conductivity type semiconductor layer; an active layer; a second conductivity type semiconductor layer; and a second conductivity type contact layer. The second conductivity type semiconductor layer includes: a carbon-doped semiconductor layer in which carbon is doped as a dopant in a compound semiconductor; and a group 2 element-doped semiconductor layer in which a group 2 element is doped as a dopant in a compound semiconductor. The carbon-doped semiconductor layer is disposed at a position closer to the active layer than the group 2 element-doped semiconductor layer.

A semiconductor optical element includes: a first conductivity type semiconductor substrate; and a laminated body disposed on the first conductivity type semiconductor substrate. The laminated body includes, in the following order from a side of the first conductivity type semiconductor substrate: a first conductivity type semiconductor layer; an active layer; a second conductivity type semiconductor layer; and a second conductivity type contact layer. The second conductivity type semiconductor layer includes: a carbon-doped semiconductor layer in which carbon is doped as a dopant in a compound semiconductor; and a group 2 element-doped semiconductor layer in which a group 2 element is doped as a dopant in a compound semiconductor. The carbon-doped semiconductor layer is disposed at a position closer to the active layer than the group 2 element-doped semiconductor layer.

A method of fabricating a gain medium includes growing a p-type layer doped with zinc on a substrate, growing an undoped layer including one or both of InP or InGaAsP on the p-type layer, growing a region that includes multiple quantum wells (MQWs) on the undoped layer, and growing an n-type layer on the region. The undoped layer has a thickness that is sufficient to prevent Zn diffusion from the p-type layer into the region during subsequent growth or wafer fabrication steps.

A light-emitting device includes an insulating base member having thermal conductivity of 10 W/m.Math.K or more; a light-emitting element that has a cathode electrode and an anode electrode and is provided on a front surface side of the base member; a capacitive element that is provided on the base member and supplies an electric current to the light-emitting element; and a reference potential wire that is provided on a rear surface side of the base member and is connected to an external reference potential. The reference potential wire is connected to the capacitive element and is insulated from the cathode electrode and the anode electrode.

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.