THz Quantum Cascade Laser AlGaAs Barrier Layer
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Solution Overview
Problem
THz-QCLs of the LO-phonon assist type have a limited maximum operating temperature, requiring large-scale cooling systems, and high threshold current density, which hinders their usability and efficiency.
Innovation Solution
The structure of THz-QCLs is modified by changing the material of barrier and well layers from GaAs to Al x Ga 1-x As, increasing the LO-phonon energy and adjusting the energy differences between levels to reduce threshold current density and increase maximum operating temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If GaAs-based semiconductor superlattice is used in THz-QCLs, then the device can achieve lasing operation, but the maximum operating temperature is limited and large-scale cooling systems are required
Solution Approach 1:
The patent changes the material composition parameter of the semiconductor superlattice from GaAs to AlxGa1-xAs, which fundamentally alters the LO-phonon energy and electron scattering properties. This parameter change enables the device to operate at higher temperatures without requiring complex cooling systems, directly resolving the contradiction between operating temperature and cooling system complexity
Solution Approach 2:
The patent employs composite material design by using AlxGa1-xAs alloy instead of pure GaAs. This composite approach allows tuning of the band structure and phonon properties through composition control, achieving both high-temperature operation and maintained lasing performance, thus resolving the temperature-cooling system contradiction
2Productivity
If GaAs-based semiconductor superlattice is used in THz-QCLs, then the device can achieve lasing operation, but the threshold current density is high which hinders usability and efficiency
Solution Approach 1:
The patent modifies the material composition parameter from GaAs to AlxGa1-xAs, which changes the effective mass and scattering rates of electrons. This parameter modification reduces the threshold current density by optimizing the balance between carrier injection and scattering losses, thereby improving lasing efficiency while reducing energy consumption
Solution Approach 2:
The patent applies different aluminum compositions (x values) in different regions of the semiconductor superlattice structure. By locally optimizing the material composition in well layers and barrier layers, the device achieves reduced threshold current density in the active region while maintaining overall structural integrity and function
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 modification results in THz-QCLs with reduced threshold current density and elevated maximum operating temperature, enhancing their usability and efficiency by allowing lasing operation at higher temperatures with electronic cooling.
Implementation Method 1
increasing the LO-phonon energy and adjusting the energy differences between levels
Implementation Method 2
stimulated emissions by way of intersubband transition are provoked among the subbands that are created in the semiconductor superlattice
Implementation Method 3
The inclined patterned potential is then used to provoke stimulated emissions by electrons in a multi stage manner, or in a cascade scheme
Data Source
Figure 1(a)~1(c)
Figure 2(a)~2(b)
Figure 3
AI summary
[PROBLEM] To manufacture a quantum cascade laser (QCL) element having a reduced threshold current density (Jth) and an increased maximum operating temperature (Tmax). [SOLUTION] One embodiment of the present invention provides a THz-QCL element (1000) with a QCL structure (100), which is a semiconductor superlattice (100A) sandwiched between a pair of electrodes (20, 30). The semiconductor superlattice (100A) (QCL structure (100)) is provided with an active region (10) that emits THz range electromagnetic waves due to the transition of electrons between sub-bands during application of a voltage to the pair of electrodes, for example. The active region (10) has repeating unit structures (10U) of a thickness, which includes sets of a well layer (10W) and a barrier layer (10B) alternatingly laminated with each other, wherein the well layer (10W) is made of AlxGa1-xAs (where 0<x<1), which is a mixed crystal of AlAs and GaAs.