Quantum Cascade Laser Layer Structure for Strain-Balanced ΔEc
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Solution Overview
Problem
Existing quantum cascade lasers face challenges in achieving a large energy difference between the conduction bands of well and barrier layers while maintaining favorable crystal quality, as increased strain can lead to lattice defects and dislocations due to mismatched lattice constants.
Innovation Solution
A quantum cascade laser design incorporating a core region with strain-compensated and lattice-matched layers, where the first well and barrier layers have higher strain, and the second well and barrier layers are lattice-matched to the substrate, reducing local strain accumulation and enhancing crystal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the absolute value of the strain of the well layer and the absolute value of the strain of the barrier layer are increased to increase the energy difference ΔEc, then the energy difference between conduction bands is improved, but local strain accumulates leading to lattice defects and dislocations
Solution Approach 1:
The injection layer is segmented into multiple well layers and barrier layers with alternating strain characteristics. Some well layers have lattice constants larger than the substrate (compressive strain) while others have lattice constants smaller than the substrate (tensile strain), dividing the strain management into discrete functional units that can be independently optimized
Solution Approach 2:
The patent applies counterbalancing strain by alternating between compressive strain well layers and tensile strain barrier layers. The tensile strain in barrier layers compensates for the compressive strain in well layers, and vice versa, preventing net strain accumulation that would lead to dislocations while maintaining the required energy difference ΔEc
2Use of energy by moving object
If strain-compensated layers with mismatched lattice constants are used to increase energy difference, then luminous efficiency is improved, but manufacturing complexity increases due to strain management requirements
Solution Approach 1:
Different well layers and barrier layers are assigned different lattice constant characteristics tailored to their specific functions. Well layers require larger lattice constants for compressive strain to achieve desired conduction band alignment, while barrier layers use smaller lattice constants for tensile strain compensation, optimizing each layer's properties for its specific role in the injection mechanism
Solution Approach 2:
The injection layer employs composite material structures combining different III-V compound semiconductor materials with varying lattice constants. By strategically selecting and combining materials such as GaInAs, AlInAs, and InP with specific composition ratios, the patent achieves both the required strain characteristics and material compatibility for efficient carrier injection
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 design achieves a large energy difference between the conduction bands, suppressing thermal leakage and improving luminous efficiency while maintaining favorable crystal quality, even at high temperatures.
Implementation Method 1
The first well layer has a lattice constant larger than a lattice constant of the substrate. The first barrier layer has a lattice constant smaller than the lattice constant of the substrate. By increasing the absolute value of the strain of the well layer and the absolute value of the strain of the barrier layer, the energy difference ΔEc between a conduction band of the well layer and a conduction band of the barrier layer can be increased.
Implementation Method 2
The second well layer and the second barrier layer each have a lattice constant that is lattice-matched to the substrate. Accumulation of local strain between the first well layer and the first barrier layer can be suppressed by the at least one lattice-matched layer
Data Source
AI summary
A quantum cascade laser includes a substrate having a group III-V compound semiconductor and a core region that is provided on the substrate and that includes a group III-V compound semiconductor. The core region includes a plurality of unit structures that are stacked on top of one another. Each of the plurality of unit structures includes an active layer and an injection layer. The injection layer includes at least one strain-compensated layer including a first well layer and a first barrier layer and at least one lattice-matched layer including a second well layer and a second barrier layer. The first well layer has a lattice constant larger than a lattice constant of the substrate. The first barrier layer has a lattice constant smaller than the lattice constant of the substrate. The second well layer and the second barrier layer each have a lattice constant that is lattice-matched to the substrate.