Quantum Well Laser Diode Structure for Strain and Carrier Confinement
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Solution Overview
Problem
Semiconductor laser diodes with quantum well structures face issues due to lattice mismatch between epitaxial layers and substrates, leading to strain accumulation, defects, and poor carrier confinement, especially at high temperatures, affecting their reliability and power conversion efficiency.
Innovation Solution
Incorporating phosphorus-containing semiconductor layers, such as AlGaAsP or GaAsP, within the multi-layer structure to reduce strain and improve carrier confinement, either as part of the active region or as a separate layer outside it, to compensate for the strain and enhance the optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If InGaAs or InAlGaAs materials are used in the well layer to improve optical gain and frequency response, then the optical performance is improved, but lattice mismatch with GaAs substrate causes strain accumulation and defects
Solution Approach 1:
The patent introduces an intermediate layer between the well layer and barrier layer to act as a mediator. This intermediate layer has a lattice constant that bridges the gap between the well layer material (InGaAs or InAlGaAs) and the barrier layer material (AlGaAsP or GaAsP), thereby reducing strain accumulation and preventing defects while maintaining the optical performance benefits of the well layer materials.
Solution Approach 2:
The patent employs composite material structures by combining multiple layers with different compositions and properties. The multi-layer structure includes well layer, intermediate layer, and barrier layer, each with specific material compositions designed to optimize both optical performance and strain management. This composite approach allows the system to achieve high optical gain while managing lattice mismatch through carefully engineered material combinations.
2Reliability
If the quantum well structure uses materials with larger bandgap difference to improve carrier confinement, then carrier confinement is improved, but strain and dislocations increase
Solution Approach 1:
The intermediate layer serves as a mediator that gradually transitions the lattice constant between the well layer and barrier layer. This gradual transition reduces the abrupt lattice mismatch that would otherwise cause dislocations, while still maintaining the necessary bandgap difference for effective carrier confinement in the quantum well structure.
Solution Approach 2:
The patent utilizes parameter changes by varying the composition and thickness of each layer to optimize both carrier confinement and strain management. By adjusting the material composition parameters (such as indium and aluminum content) and layer thickness parameters, the system achieves adequate carrier confinement without excessive strain accumulation that would lead to dislocations.
3Power
If epitaxial layer thickness is increased to improve optical output, then optical power is improved, but strain accumulation and defect density increase
Solution Approach 1:
The patent applies segmentation by dividing the epitaxial structure into multiple thin layers (well layer, intermediate layer, barrier layer) rather than using a single thick layer. This segmented structure allows the total optical active region to achieve high optical output power while each individual layer remains thin enough to avoid excessive strain accumulation and defect formation.
Solution Approach 2:
The multi-layer composite structure enables the system to achieve high optical output power through the cumulative effect of multiple layers, while each layer's thickness is controlled to remain below the critical thickness for defect formation. The composite structure distributes the strain across multiple interfaces rather than concentrating it in a single thick 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
The phosphorus-containing layers effectively reduce defects and dislocations, improve carrier confinement, and enhance the power conversion efficiency and reliability of semiconductor laser diodes, particularly at high temperatures, by adjusting the strain and energy band offsets.
Implementation Method 1
If the material of the grown epitaxial layer is not lattice-matched to the substrate, strain will be generated in the epitaxial layer, and the accumulated excessive strain in the epitaxial layer may cause defects or dislocations
Implementation Method 2
the well layer is usually formed of a semiconductor material with a lower bandgap (narrower bandgap), and the barrier layer is composed of a material with a larger bandgap (wider bandgap) than the well layer. Consequently, a quantum well is formed by the bandgap difference between the barrier layer and the well layer
Implementation Method 3
When the laser diode is forward biased, electrons and holes are injected and confined to the quantum well structure, and the injected electrons and holes will recombine in the quantum well to emit light of a specific wavelength
Implementation Method 4
The light produces constructive interference in the resonant cavity, which in turn emits laser light
Data Source
AI summary
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.