Disclosed herein is a semiconductor device. The semiconductor device includes a substrate, a first conductive type semiconductor layer disposed over the substrate, an active layer disposed over the first conductive type semiconductor layer, and a second conductive type semiconductor layer disposed over the active layer. The first conductive type semiconductor layer includes a first layer, a second layer and a third layer having different composition ratios of indium (In). The first semiconductor layer is disposed close to the active layer. The second semiconductor layer is disposed under the first semiconductor layer. The third semiconductor layer is disposed under the second semiconductor layer. In content is reduced from the active layer to the third semiconductor layer, and In content of the third semiconductor layer may be 5% or more to 10% or less of that of the active layer.

Disclosed herein is a semiconductor device. The semiconductor device includes a substrate, a first conductive type semiconductor layer disposed over the substrate, an active layer disposed over the first conductive type semiconductor layer, and a second conductive type semiconductor layer disposed over the active layer. The first conductive type semiconductor layer includes a first layer, a second layer and a third layer having different composition ratios of indium (In). The first semiconductor layer is disposed close to the active layer. The second semiconductor layer is disposed under the first semiconductor layer. The third semiconductor layer is disposed under the second semiconductor layer. In content is reduced from the active layer to the third semiconductor layer, and In content of the third semiconductor layer may be 5% or more to 10% or less of that of the active layer.

A method of manufacturing a semiconductor laser device includes: forming an n-type nitride semiconductor layer; forming a first layer comprising In.sub.aGa.sub.1-aN (0<a<1) above the n-type nitride semiconductor layer; forming a second layer and a third layer above the first layer; forming an active layer having a single quantum well structure or a multiple quantum well structure above the second layer and the third layer; and forming a p-type nitride semiconductor layer above the active layer.

A semiconductor laser device includes an n-type nitride semiconductor layer; a first layer disposed above the n-type nitride semiconductor and composed of In.sub.aGa.sub.1-aN (0a<1); a second layer disposed above the first layer and composed of In.sub.bGa.sub.1-bN (0<b<1, a<b), the second layer having a thickness smaller than that of the first layer and containing an n-type impurity; a third layer composed of In.sub.cGa.sub.1-cN (0c<1, c<b) and having a thickness smaller than that of the second layer, the third layer being disposed on (i) a surface of the second layer on the active layer side and/or (ii) a surface of the second layer on the first layer side; an active layer disposed above the second layer and the third layer, and having a single quantum well structure or a multiple quantum well structure; and a p-type nitride semiconductor layer disposed above the active layer.

An edge-emitting semiconductor laser and a method for operating a semiconductor laser are disclosed. The edge-emitting semiconductor laser includes an active zone within a semiconductor layer sequence and a stress layer. The active zone is configured for being energized only in a longitudinal strip perpendicular to a growth direction of the semiconductor layer sequence. The semiconductor layer sequence has a constant thickness throughout in the region of the longitudinal strip so that the semiconductor laser is gain-guided. The stress layer may locally stress the semiconductor layer sequence in a direction perpendicular to the longitudinal strip and in a direction perpendicular to the growth direction. A refractive index of the semiconductor layer sequence, in regions which, seen in plan view, are located next to the longitudinal strip, for the laser radiation generated during operation is reduced by at least 210.sup.4 and by at most 510.sup.3.

The invention relates to a quantum cascade laser (300) comprising a gain region (102) inserted between two optical confinement layers (104.sub.1, 104.sub.2), said gain region (102) having an electron input into the gain region (102) and an electron output from said gain region (102) characterized in that said laser comprises a hole-blocking area (304) on the side of said electron output.

A light emitting element includes a stacked structure 20 in which a first compound semiconductor layer 21, an active layer 23 and a second compound semiconductor layer 22 made of GaN-based compound semiconductors are stacked, a mode loss acting portion 54 provided on the second compound semiconductor layer 22 and configuring a mode loss acting region 55 that acts upon increase or decrease of oscillation mode loss, a second electrode 32, a second light reflection layer 42, a first light reflection layer 41, and a first electrode 31. A current injection region 51, a current non-injection inner side region 52 that surrounds the current injection region 51 and a current non-injection outer side region 53 that surrounds the current non-injection inner side region 52 are formed on the stacked structure 20, and a projection image of the mode loss acting region 55 and a projection image of the current non-injection outer side region 53 overlap with each other.

An edge-emitting semiconductor laser and a method for operating a semiconductor laser are disclosed. In an embodiment, the edge-emitting semiconductor laser includes an active zone within a semiconductor layer sequence and a stress layer. The active zone is configured for being energized only in a longitudinal strip perpendicular to a growth direction of the semiconductor layer sequence. The semiconductor layer sequence has a constant thickness throughout in the region of the longitudinal strip so that the semiconductor laser is gain-guided. The stress layer may locally stress the semiconductor layer sequence in a direction perpendicular to the longitudinal strip and in a direction perpendicular to the growth direction. A refractive index of the semiconductor layer sequence, in regions which, seen in plan view, are located next to the longitudinal strip, for the laser radiation generated during operation is reduced by at least 210.sup.4 and by at most 510.sup.3.

A light emitting device includes a substrate, a buffer layer, a first active layer, and a plurality of mesa regions. A portion of the first active layer includes a first electrical polarity. The plurality of mesa regions includes at least a portion of the first active layer, a light emitting region on the portion of the first active layer, and a second active layer on the light emitting region. A portion of the second active layer includes a second electrical polarity. The light emitting region is configured to emit light which has a target wavelength between 200 nm to 300 nm. A thickness of the light emitting region is a multiple of the target wavelength, and a dimension of the light emitting region parallel to the thickness is smaller than 10 times the target wavelength, such that the emitted light is confined to fewer than 10 transverse modes.

An aluminium gallium indium phosphide (AlGaInP)-based semiconductor laser device is provided. On a main surface of a semiconductor substrate formed of n-type GaAs (gallium arsenide), from the bottom layer, an n-type buffer layer, an n-type cladding layer formed of an AlGaInP-based semiconductor containing silicon (Si) as a dopant, an active layer, a p-type cladding layer formed of an AlGaInP-based semiconductor containing magnesium (Mg) or zinc (Zn) as a dopant, an etching stopper layer, and a p-type contact layer are formed. Here, when an Al composition ratio x of the AlGaInP-based semiconductor is taken as a composition ratio of Al and Ga defined as (Al.sub.xGa.sub.1-x).sub.0.5In.sub.0.5P, a composition of the n-type cladding layer is expressed as (Al.sub.xnGa.sub.1-xn).sub.0.5In.sub.0.5P (0.9<xn<1) and a composition of the p-type cladding layer is expressed as (Al.sub.xpGa.sub.1-xp).sub.0.5In.sub.0.5P (0.9<xp1), and xn and xp satisfy a relationship of xn<xp.