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.

In an example, the present invention provides a method for fabricating a light emitting device configured as a Group III-nitride based laser device. The method also includes forming a gallium containing epitaxial material overlying the surface region of a substrate member. The method includes forming a p-type (Al,In,Ga)N waveguiding material overlying the gallium containing epitaxial material under a predetermined process condition. The method includes maintaining the predetermined process condition such that an environment surrounding a growth of the p-type (Al,In,Ga)N waveguide material is substantially a molecular N.sub.2 rich gas environment. The method includes maintaining a temperature ranging from 725 C to 925 C during the formation of the p-type (Al,In,Ga)N waveguide material, although there may be variations. In an example, the predetermined process condition is substantially free from molecular H.sub.2 gas.

A semiconductor laser including an active zone and a waveguide, wherein the active zone includes an active layer configured to generate electromagnetic radiation during operation of the semiconductor laser, the waveguide is configured to guide the electromagnetic radiation generated during operation of the semiconductor laser within the semiconductor laser, the waveguide includes a subregion formed from a compound semiconductor material, wherein a proportion of a material of the compound semiconductor material gradually increases in the entire subregion along the vertical direction toward the active zone so that a refractive index of the subregion gradually decreases toward the active zone, and the proportion is an aluminum proportion or a phosphorus proportion.

A two-dimensional photonic crystal laser with transparent conductive cladding layer is provided. The two-dimensional photonic crystal region through the etching process is composed by multiple periodic air-holes with proper duty cycle. Then, the transparent conductive oxide layer is directly deposited on the top of the entire two-dimensional photonic crystal structure to cover the entire two-dimensional photonic crystal structure in order to form a current spreading layer. The configuration and the process condition of transparent conductive oxide layer are optimized to provide uniform current spreading path and the transparency. In addition to simplifying the whole fabrication process, the optical confinement is improved and the maximum gain to optical feedback is obtained. Overall, low threshold, small divergence angle and high quality laser output is achieved to satisfy the requirements for next-generation light sources.

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 two-dimensional photonic crystal laser with transparent conductive cladding layer is provided. The two-dimensional photonic crystal region through the etching process is composed by multiple periodic air-holes with proper duty cycle. Then, the transparent conductive oxide layer is directly deposited on the top of the entire two-dimensional photonic crystal structure to cover the entire two-dimensional photonic crystal structure in order to form a current spreading layer. The configuration and the process condition of transparent conductive oxide layer are optimized to provide uniform current spreading path and the transparency. In addition to simplifying the whole fabrication process, the optical confinement is improved and the maximum gain to optical feedback is obtained. Overall, low threshold, small divergence angle and high quality laser output is achieved to satisfy the requirements for next-generation light sources.

An electrically pumped surface-emitting photonic crystal laser includes an electric currents confinement structure arranged on a photonic crystal structure and an active layer with an opening, a transparent conducting layer arranged on the electric currents confinement structure and covering the photonic crystal structure, a metal anode arranged on the transparent conducting layer with an aperture. The photonic crystal laser has its epitaxy structure etched from above to fabricate the photonic crystal to allow laser beams to pass through with conductivity for the purpose of electrically pumping a quantum structure without complex technologies of wafer fusion bonding or epitaxial regrowth. Thereby the laser beams can be emitted from a front surface of the epitaxy structure with a narrow divergence angle.

A quantum cascade laser has an active layer, a first and second cladding layer, and an optical guide layer. The active layer has a plurality of injection quantum well regions and a plurality of light-emitting quantum well regions. The each of the injection quantum well regions and the each of the light-emitting quantum well regions are alternatively stacked. The first and second cladding layers are provided to interpose the active layer from both sides, and have a refractive index lower than an effective refractive index of the each of the light-emitting quantum well regions. The optical guide layer is disposed to divide the active layer into two parts. The optical guide layer has a refractive index higher than the effective refractive index of the each of the light-emitting quantum well regions, and has a thickness greater than the thickness of all well layers of quantum well layers.

A surface-emitting laser device includes a first electrode, a lower cladding layer, an active layer, an upper cladding layer, a relaxation layer, a contacting layer having a bandgap different from that of the upper cladding layer, a second electrode, and a photonic crystal layer provided between the lower cladding layer and the active layer or between the active layer and the upper cladding layer, including a basic region and a plurality of different refractive index regions that differ in refractive index from the basic region and are distributed two-dimensionally in a plane perpendicular to a thickness direction to form a resonance mode of light in the plane. The relaxation layer has a bandgap that is between a bandgap of the upper cladding layer and a bandgap of the contacting layer.

In an example, the present invention provides a method for fabricating a light emitting device configured as a Group III-nitride based laser device. The method also includes forming a gallium containing epitaxial material overlying the surface region of a substrate member. The method includes forming a p-type (Al,In,Ga)N waveguiding material overlying the gallium containing epitaxial material under a predetermined process condition. The method includes maintaining the predetermined process condition such that an environment surrounding a growth of the p-type (Al,In,Ga)N waveguide material is substantially a molecular N.sub.2 rich gas environment. The method includes maintaining a temperature ranging from 725 C to 925 C during the formation of the p-type (Al,In,Ga)N waveguide material, although there may be variations. In an example, the predetermined process condition is substantially free from molecular H.sub.2 gas.