An optical semiconductor device outputting a predetermined wavelength of laser light includes a quantum well active layer positioned between a p-type cladding layer and an n-type cladding layer in thickness direction. The optical semiconductor device includes a separate confinement heterostructure layer positioned between the quantum well active layer and the n-type cladding layer. The optical semiconductor device further includes an electric-field-distribution-control layer positioned between the separate confinement heterostructure layer and the n-type cladding layer and configured by at least two semiconductor layers having band gap energy greater than band gap energy of a barrier layer constituting the quantum well active layer. The quantum well active layer is doped with 0.3 to 1×10.sup.18/cm.sup.3 of n-type impurity.

An active layer of a quantum cascade laser includes an active layer includes a plurality of emission regions and a plurality of injection regions. Each emission region includes an injection barrier layer, and an light-emitting quantum well layer that has at least two well layers, and that emits infrared light by undergoing an intersubband transition. Each injection region includes an extraction barrier layer, and a relaxation quantum well layer that creates an energy level for relaxing the energy of carriers from the each emission region. One of adjacent two well layers in the light-emitting quantum well layer of the each emission region on the side of the extraction barrier layer is deeper than a second well layer on the side of the injection barrier layer. The each emission region and the injection region are alternately stacked.

Provided here are: semiconductor layers comprised of an n-type cladding layer formed on a surface of an n-type GaAs substrate, active layers formed on surfaces of the n-type cladding layer, p-type cladding layers formed on surfaces of the active layers, and p-type contact layers formed on surfaces of the p-type cladding layers, the p-type cladding layers and the p-type contact layers being formed to have a ridges; insulating films covering surfaces of the semiconductor layers but having openings on surfaces of the p-type contact layer; and conductive layers connected to the p-type contact layers through the openings, the conductive layers being formed on surfaces of the insulating films to cover planar portions provided in the semiconductor layers adjacently to the ridges; wherein, together with the conductive layers, convex sidewalls are provided to be placed over portions of the planar portions at their sides nearer to the ridges.

An optical semiconductor device outputting a predetermined wavelength of laser light includes a quantum well active layer positioned between a p-type cladding layer and an n-type cladding layer in thickness direction. The optical semiconductor device includes a separate confinement heterostructure layer positioned between the quantum well active layer and the n-type cladding layer. The optical semiconductor device further includes an electric-field-distribution-control layer positioned between the separate confinement heterostructure layer and the n-type cladding layer and configured by at least two semiconductor layers having band gap energy greater than band gap energy of a barrier layer constituting the quantum well active layer. The optical semiconductor device is applied to a ridge-stripe type laser.

A quantum-cascade laser element includes: an embedding layer including a first portion formed on a side surface of a ridge portion, and a second portion extending from an edge portion of the first portion along a width direction of a semiconductor substrate; and a metal layer formed at least on a top surface of the ridge portion and on the first portion. A surface of the first portion has a first inclined surface inclined with respect to the side surface to go away from the side surface as going away from the semiconductor substrate, and a second inclined surface located opposite to the semiconductor substrate with respect to the first inclined surface and inclined with respect to a center line to approach the center line as going away from the semiconductor substrate. The metal layer extends over the first inclined surface and the second inclined surface.

A method for passivating sidewalls of patterned semiconductor wafer including ridge(s). The method includes: depositing first layer of first dielectric material on pattern surface of said wafer; etching portion of first layer to obtain tapered portions of first dielectric material along sidewall(s) of ridge(s); depositing second layer of second dielectric material on tapered portions and said wafer; depositing photo-sensitive material on second layer; aligning mask with photo-sensitive material, wherein portion(s) of photo-sensitive material corresponding to top surface of ridge(s) is/are unmasked, and remaining portion is masked; applying developing solution and exposing photo-sensitive material to remove portion(s) of photo-sensitive material; etching portion(s) of second layer that is/are deposited on top surface of ridge(s); and removing photo-sensitive material.

A laser diode includes a ridge portion, channel portions located adjacent to the ridge portion such that the ridge portion is sandwiched, the channel portions being shorter in height than the ridge portion, terrace portions adjacent to opposite sides of the respective channel portions from the ridge portion and longer in height than the channel portions, supporting portions provided over the respective channel portions, separated from side surfaces of the ridge portion or side surfaces of terrace portions or both, and made of resin, a ceiling portion including first portions provided over the supporting portions and second portions continuous with the first portions and located over the respective channel portions with hollow portions interposed therebetween, the ceiling portion being made of resin, and a metal layer provided over the ceiling portion and connected to an upper surface of the ridge portion.

An optical semiconductor device outputting a predetermined wavelength of laser light includes a quantum well active layer positioned between a p-type cladding layer and an n-type cladding layer in thickness direction. The optical semiconductor device includes a separate confinement heterostructure layer positioned between the quantum well active layer and the n-type cladding layer. The optical semiconductor device further includes an electric-field-distribution-control layer positioned between the separate confinement heterostructure layer and the n-type cladding layer and configured by at least two semiconductor layers having band gap energy greater than band gap energy of a barrier layer constituting the quantum well active layer. The optical semiconductor device is applied to a ridge-stripe type laser.

A light emitter includes a substrate, a first semiconductor layer having a first conductivity type, a second semiconductor layer having a second conductivity type different from the first conductivity type, a light emitting layer provided between the first semiconductor layer and the second semiconductor layer and capable of emitting light when current is injected into the light emitting layer, and a third semiconductor layer provided between the substrate and the first semiconductor layer and having the second conductivity type, in which the first semiconductor layer is provided between the third semiconductor layer and the light emitting layer, and the third semiconductor layer has a protruding/recessed structure.

In an example, the present invention provides a gallium and nitrogen containing laser diode device. The device has a gallium and nitrogen containing substrate material comprising a surface region, which is configured on either a ({10-10}) crystal orientation or a {10-10} crystal orientation configured with an offcut at an angle toward or away from the [0001] direction. The device also has a GaN region formed overlying the surface region, an active region formed overlying the surface region, and a gettering region comprising a magnesium species overlying the surface region. The device has a p-type cladding region comprising an (InAl)GaN material doped with a plurality of magnesium species formed overlying the active region.