Semiconductor Laser Diode Guiding Layers for Differential Resistance
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Solution Overview
Problem
Conventional semiconductor laser diodes experience increased differential resistance due to band bending at the interface between guiding layers and the active layer, which degrades optical confinement and efficiency, especially at higher temperatures.
Innovation Solution
Incorporating an un-doped AlGaInAs first guiding layer with a carrier concentration less than 1×10^11 cm^-3 between the n-type cladding layer and the active layer, and a second guiding layer with a different composition, such as GaInAsP, to suppress band bending and maintain effective carrier confinement, while adjusting the thickness of these layers for enhanced optical confinement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If doped guiding layers are used to lower differential resistance, then electrical conductivity is improved, but band bending occurs at the interface with the active layer which degrades optical confinement
Solution Approach 1:
The guiding layer is divided into two separate layers: a first guiding layer that is un-doped or lightly doped to maintain optical confinement and suppress band bending, and a second guiding layer that is doped to provide low differential resistance. This segmentation allows each layer to independently fulfill its specific function without compromising the other.
Solution Approach 2:
Different doping levels are applied to different regions (layers) of the guiding structure. The first guiding layer has low or zero doping to preserve optical properties near the active layer, while the second guiding layer has higher doping to reduce electrical resistance in the outer region.
2Stability of the object's composition
If the band gap wavelength of the first guiding layer is made shorter than 1.1 μm, then optical confinement efficiency is enhanced, but band bending increases at the interface with the active layer
Solution Approach 1:
The guiding structure is segmented into two layers with different band gap wavelengths and doping levels. The first guiding layer has a shorter band gap wavelength for optical confinement, while the second guiding layer has a longer band gap wavelength and higher doping to compensate for band bending effects.
Solution Approach 2:
The second guiding layer acts as an intermediary between the first guiding layer and the cladding layer, providing a transition region that reduces band bending while maintaining the optical confinement properties established by the first guiding layer.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration reduces differential resistance and maintains optical confinement, enabling the laser diode to operate efficiently at higher temperatures with improved series resistance and carrier confinement characteristics.
Implementation Method 1
the band bending within the second guiding layer may be suppressed due to the un-doped first guiding layer
Implementation Method 2
a plurality of guiding layers to enhance the optical confinement efficiency, where layers closer to the active layer have a composition to show the higher refractive index
Implementation Method 3
an active layer including AlGaInAs or AlInAs often provides the first guiding layer, which is apart from the active layer, with a band gap wavelength shorter than 1.1 μm
Data Source
AI summary
The present application provides a laser diode that enables to reduce the differential resistance. The laser diode of the invention provides first and second guiding layer in an n-side of an active layer. The first guiding layer is put between the active layer and the n-type cladding layer; while, the second guiding layer is put between the first cladding layer and the active layer. These first and second guiding layers are intrinsic layers or p-type layers, where the conduction band level of the second guiding layer is lower than that of the first guiding layer, while the band gap wavelength of the first guiding layer is shorter than that of the second guiding layer.