Graded Multiple Quantum Well Structure for Stress Management
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Solution Overview
Problem
The accumulation of stress in multiple quantum well structures due to lattice mismatch between grown heterostructure materials leads to epitaxial defects and reduced light emission efficiency, as the stress exceeds the material's threshold and must be released, causing damage to the structure.
Innovation Solution
A multiple quantum well structure is designed with well-barrier sets where the thickness of well layers decreases and intermediate level layers increase along a direction, reducing stress and ensuring a consistent wavelength of light emission, thereby maintaining good epitaxial quality and optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If heterostructure materials with lattice mismatch are grown to increase thickness, then the quantum well structure can be more fully formed, but stress accumulates and exceeds threshold causing epitaxial defects
Solution Approach 1:
The patent divides the quantum well structure into multiple periods, each containing well layers and barrier layers with specific thickness ratios. By segmenting the structure into repeating units with controlled dimensions, the stress accumulation is distributed and managed across periods, preventing catastrophic failure while maintaining structural quality.
Solution Approach 2:
The patent systematically varies the thickness parameters of well layers and barrier layers across different periods. Specifically, the well layer thickness decreases while barrier layer thickness increases in successive periods, which progressively adjusts the stress state to remain below the threshold for epitaxial defects while preserving optical performance.
2Use of energy by moving object
If material layers are reduced to nanometer scale to enhance quantum effects, then light emission efficiency is improved, but the structure becomes more sensitive to stress and lattice mismatch
Solution Approach 1:
The patent employs composite heterostructure materials (e.g., InGaN/GaN, InAlGaN/GaN) with carefully engineered band gaps and lattice constants. By combining materials with complementary properties in a multi-period structure, the design achieves enhanced quantum confinement for efficient light emission while the composite nature provides stress management capability to maintain structural integrity at nanometer scales.
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 structured multiple quantum well design reduces stress and ensures consistent light emission, enhancing both epitaxial quality and optical properties by managing layer thicknesses and bandgaps to maintain material integrity and emission efficiency.
Implementation Method 1
when a material is reduced to nanometer scale in a direction, the quantum confinement effect will appear in the direction. At this moment, the electrons are confined to move freely in a two-dimensional space constituted by the other two dimensions, and such system is called a quantum well.
Implementation Method 2
The quantum well utilizes a semiconductor layer having a larger band gap as a barrier layer and a semiconductor layer having a smaller band gap as a well layer. In the quantum well, which is a well-like band structure formed by the well layer clamped by the barrier layers from two sides, carriers are easily confined, thus enhancing light emission efficiency.
Implementation Method 3
When lattices of two grown heterostructure materials do not match each other, stress will accumulate in the structure. As growing thickness increases, the accumulated stress increases. When the stress exceeds a threshold value, the material layers cannot bear the stress anymore and the stress has to be released in other ways. Accordingly, epitaxial defects are usually caused, leading to damage to the multiple quantum well structure.
Data Source
AI summary
A multiple quantum well structure includes a plurality of well-barrier sets arranged along a direction. Each of the well-barrier sets includes a barrier layer, at least one intermediate level layer, and a well layer. A bandgap of the barrier layer is greater than an average bandgap of the intermediate level layer, and the average bandgap of the intermediate level layer is greater than a bandgap of the well layer. The barrier layers, the intermediate level layers, and the well layers of the well-barrier sets are stacked by turns. Thicknesses of at least parts of the well layers in the direction gradually decrease along the direction, and thicknesses of at least parts of the intermediate level layers in the direction gradually increase along the direction. A method for manufacturing a multiple quantum well structure is also provided.