Asymmetric Three-Coupled Quantum Wells for Low-Voltage Light Absorption
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Solution Overview
Problem
Existing optical devices with three-coupled quantum well structures face challenges in reducing driving voltage while maintaining high light absorption intensity, particularly in three-dimensional camera applications using time-of-flight algorithms.
Innovation Solution
The optical device incorporates a three-coupled quantum well structure with asymmetric multi-energy levels, featuring a first, second, and third quantum well layer with specific energy band gaps and thicknesses, coupled by barriers that allow electron and hole tunneling, and is integrated with outer barriers and micro cavity layers to optimize light absorption and reduce driving voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional three-coupled quantum well structure is used, then the device can operate with standard driving voltage, but the light absorption intensity is insufficient
Solution Approach 1:
The patent applies asymmetry by designing the three-coupled quantum well structure with non-uniform well widths and asymmetric barrier configurations. Specifically, the first, second, and third quantum wells have different widths (e.g., 5nm, 7nm, 5nm), and the coupling barriers have asymmetric thicknesses or positions. This asymmetric design creates favorable wave function overlap between electron and hole states, enhancing light absorption intensity while allowing operation at reduced driving voltages compared to symmetric structures.
Solution Approach 2:
The patent implements local quality by varying the material composition and structural parameters at different positions within the quantum well structure. Different quantum wells use different material compositions (e.g., varying InGaAsP compositions), and the coupling barriers have locally optimized thicknesses and positions. This localized optimization of structural quality enhances carrier confinement and wave function overlap in specific regions, improving light absorption efficiency without requiring uniform high-voltage operation across the entire structure.
2Illumination intensity
If the quantum well layer thickness is increased to improve light absorption, then the absorption intensity increases, but the driving voltage also increases
Solution Approach 1:
The patent applies segmentation by dividing the active region into three separate coupled quantum wells instead of using a single thick quantum well. Each quantum well has an optimized thickness (e.g., 5nm, 7nm, 5nm) that balances light absorption with carrier confinement. The segmentation into multiple thinner wells coupled through barriers allows the structure to achieve high overall absorption intensity while maintaining thinner individual layers, thereby reducing the required driving voltage compared to a single thick well structure.
Solution Approach 2:
The patent transitions from a single-dimension thickness parameter to a multi-dimensional structural optimization by introducing vertical coupling between three quantum wells. Instead of simply increasing the thickness of one well, the invention creates a coupled system where the interaction between wells (through coupling barriers) provides an additional degree of freedom for optimizing both absorption intensity and driving voltage. This dimensional approach allows independent optimization of each well's thickness while achieving high overall performance.
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 enhances light absorption intensity while reducing the driving voltage required, improving the performance of optical devices such as optical modulators and semiconductor devices by increasing the transition energy without increasing the applied voltage.
Implementation Method 1
A thickness of the first coupling barrier may allow tunneling of an electron and a hole through the first coupling barrier and a thickness of the second coupling barrier may allow the tunneling of the electron and the hole through the second coupling barrier
Implementation Method 2
an optical device including a three-coupled quantum well structure having asymmetric multi-energy levels, in which a driving voltage of the three-coupled quantum well structure may be reduced while maintaining a high light absorption intensity
Data Source
AI summary
Provided is an optical device including an active layer, which includes two outer barriers and a coupled quantum well between the two outer barriers. The coupled quantum well includes a first quantum well layer, a second quantum well layer, a third quantum well layer, a first coupling barrier between the first quantum well layer and the second quantum well layer, and a second coupling barrier between the second quantum well layer and the third quantum well layer. The second quantum well layer is between the first quantum well layer and the third quantum well layer. An energy band gap of the second quantum well layer is less than an energy band gap of the first quantum well layer, and an energy band gap of the third quantum well layer is equal to or less than the energy band gap of the second quantum well layer.