A quantum dot (QD) laser comprises a semiconductor substrate and an active region epitaxially deposited on the semi-conductor substrate. The active region includes a plurality of barrier layers and a plurality of QD layers interposed between each of the plurality of barrier layers. A net compressive strain associated with the plurality of QD layers is maintained below a maximum allowable strain to prevent formation of misfit dislocations within the active region of the QD laser.

Provided is a semiconductor laser diode, including a GaAs/In P substrate and a multi-layer structure on the GaAs/InP substrate. The multi-layer structure includes a lower epitaxial region, an active region and an upper epitaxial region. The active region comprises a first active layer, an epitaxial region and a second active layer, the epitaxial region is disposed between the first active layer and the second active layer, the first active layer comprises one or more quantum well structures or one or more quantum dot structures, and the second active layer comprises one or more quantum well structures or one or more quantum dot structures. the epitaxial region further comprises a tunnel junction and at least one carrier confinement layer, at least one carrier confinement layer is disposed between the tunnel junction and the first active layer or between the tunnel junction and the second active layer such that the at least one carrier confinement layer blocks electrons or holes, and no electrons or holes are able to reach the tunnel junction.

Provided is a semiconductor laser diode. Although the materials used in the conventional technology can reduce the strain, the selections of materials are relatively limited and the carrier confinement ability is not good. To solve the above-mentioned problems, a phosphorus-containing semiconductor layer is provided in a laser diode. As such, it can effectively reduce the strain of the active region or the total strain of the laser diode, and improve the carrier confinement capability of the active region. Therefore, it can effectively reduce the total strain or significantly improve carrier confinement under appropriate conditions of the laser diode. In some cases, it has the aforesaid effects. The phosphorus-containing semiconductor layer is suitable for an active region with one or more active layers. Especially after the phosphorus-containing semiconductor layer is provided in the active region with multiple active layers, high temperature performance are significantly improved or enhanced.

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.

In a semiconductor laser device, a n-type cladding layer, a multi-quantum well active layer, and a p-type cladding layer are sequentially laminated on an n-type substrate, and a stripe structure is provided on this semiconductor laminated section. The n-type cladding layer has a first n-type cladding layer configured of Al.sub.x1Ga.sub.1-x1As (0.4<x11), and a second n-type cladding layer configured of (Al.sub.x2Ga.sub.1-x2).sub.1-y2In.sub.y2P (0x21, 0.45y20.55). The p-type cladding layer is configured of (Al.sub.x3Ga.sub.1-x3).sub.1-y3In.sub.y3P (0x31, 0.45y30.55). The width of the stripe structure is 10 m or more, and the refractive index with respect to the laser oscillation wavelength of the first n-type cladding layer is less than or equal to the refractive index with respect to the laser oscillation wavelength of the second n-type cladding layer.

A semiconductor laser device of an embodiment comprises: a first electrode having an opening for passage of laser light and arranged on a main surface of a substrate; and a second electrode arranged on a back surface of the substrate. A stacked structural body including an active layer and a photonic crystal layer is arranged between the substrate and the first electrode, and a current confinement layer having an opening for passage of a current is arranged between the stacked structural body and the first electrode. A maximum width of the opening of the current confinement layer is smaller than a maximum width of the opening of the first electrode, and a whole region defined by the opening of the current confinement layer fits within a region defined by the opening of the first electrode as viewed from the first electrode side toward the second electrode side.

In a semiconductor laser device, a n-type cladding layer, a multi-quantum well active layer, and a p-type cladding layer are sequentially laminated on an n-type substrate, and a stripe structure is provided on this semiconductor laminated section. The n-type cladding layer has a first n-type cladding layer configured of Al.sub.x1Ga.sub.1-x1As (0.4<x11), and a second n-type cladding layer configured of (Al.sub.x2Ga.sub.1-x2).sub.1-y2In.sub.y2P (0x21, 0.45y20.55). The p-type cladding layer is configured of (Al.sub.x3Ga.sub.1-x3).sub.1-y3In.sub.y3P (0x31, 0.45y30.55). The width of the stripe structure is 10 m or more, and the refractive index with respect to the laser oscillation wavelength of the first n-type cladding layer is less than or equal to the refractive index with respect to the laser oscillation wavelength of the second n-type cladding layer.

A semiconductor laser device of an embodiment comprises: a first electrode having an opening for passage of laser light and arranged on a main surface of a substrate; and a second electrode arranged on a back surface of the substrate. A stacked structural body including an active layer and a photonic crystal layer is arranged between the substrate and the first electrode, and a current confinement layer having an opening for passage of a current is arranged between the stacked structural body and the first electrode. A maximum width of the opening of the current confinement layer is smaller than a maximum width of the opening of the first electrode, and a whole region defined by the opening of the current confinement layer fits within a region defined by the opening of the first electrode as viewed from the first electrode side toward the second electrode side.

A high-efficiency active layer includes a strained quantum well layer and, at one side thereof, a first strained barrier layer configured to transport electrons. The first strained barrier layer and the strained quantum well layers are configured to form strain compensation. A second barrier layer is positioned on the other side of the strained quantum well layer and is configured to transport holes. A band offset between conduction bands of the first strained barrier layer and of the strained quantum well layer is less than a band offset between valence bands of the strained quantum well layer and of the first strained barrier layer. A band offset between valence bands of the strained quantum well layer and of the second barrier layer is less than a band offset between conduction bands of the second barrier layer and of the strained quantum well layer. Light-emitting efficiency and reliability are improved.

The light-emitting element of an embodiment outputs a clear optical image while suppressing light output efficiency reduction, and includes a substrate, a light-emitting unit, and a bonding layer. The light-emitting unit has a semiconductor stack, including a phase modulation layer, between first and second electrodes. The phase modulation layer has a base layer and modified refractive index regions, and includes a first region having a size including the second electrode, and a second region. Each gravity center of the second region's modified refractive index region is arranged by an array condition. The light from the stack is a single beam, and regarding a first distance from the substrate to the stack's front surface and a second distance from the substrate to the stack's back surface, a variation amount of the first distance along a direction on the substrate is smaller than a variation amount of the second distance.