Graded Barrier Multi-Quantum Well Structure for LED Efficiency
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Solution Overview
Problem
Conventional multi-quantum well structures in LEDs suffer from low emitting efficiency due to the slower movement of holes compared to electrons, resulting in uneven arrangement and reduced photon emission, as holes face greater resistance across barrier layers with larger energy band gaps.
Innovation Solution
Incorporating a composition grading barrier layer with a gradually transitioning conduction and forbidden band, specifically using GaN or AlGaN semiconductor layers doped with In or Al, to reduce the energy band difference between barrier and well layers, facilitating easier hole movement and even distribution of charge carriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional barrier layers with large energy band gap are used to confine charge carriers, then carrier confinement is improved, but hole movement speed decreases and emitting efficiency deteriorates
Solution Approach 1:
The patent applies parameter changes by gradually transitioning the composition ratio of AlGaN in the barrier layer from high Al content at the bottom to low Al content at the top, creating a composition gradient that modifies the energy band structure. This gradient allows for improved hole transport while maintaining effective carrier confinement, resolving the contradiction between reliability and productivity.
Solution Approach 2:
The patent implements local quality by creating different composition regions within the barrier layer - the bottom portion has high Al content for strong confinement, while the top portion has low Al content for easy hole extraction. This spatial variation in material composition allows simultaneous optimization of both carrier confinement and hole movement efficiency.
2Reliability
If barrier layers with large energy band gap are used, then carrier confinement is improved, but hole movement resistance increases
Solution Approach 1:
The patent changes the composition parameter of AlGaN gradually across the barrier layer thickness, creating a parameter gradient that reduces hole movement resistance at the top interface while maintaining strong confinement at the bottom interface. This resolves the contradiction between carrier confinement and hole movement ease.
Solution Approach 2:
The composition gradient in the barrier layer acts as an intermediary that mediates between the high confinement requirement and the low resistance requirement. The gradual transition in Al content provides a smooth energy band profile that facilitates hole movement while preserving confinement effectiveness.
3Device complexity
If conventional uniform barrier layers are used, then structure simplicity is maintained, but charge carrier distribution uniformity deteriorates
Solution Approach 1:
The patent applies local quality by creating a composition gradient within the barrier layer, where different regions have different Al content to optimize local functions. The bottom region provides strong confinement while the top region facilitates hole extraction, achieving uniform charge carrier distribution without excessive structural complexity.
Solution Approach 2:
The patent introduces parameter changes in the form of a composition gradient across the barrier layer thickness. This gradual change in Al content creates a corresponding gradient in energy band structure, which promotes uniform charge carrier distribution while maintaining a relatively simple layered structure.
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 approach enhances the even arrangement of electrons and holes within the multi-quantum well structure, leading to improved emitting efficiency by reducing resistance for hole movement and increasing the number of holes in the well layer, thus boosting the overall LED emission efficiency.
Implementation Method 1
a second barrier layer is provided between the two well layers, wherein conduction band and forbidden band of the second barrier layer gradually transit to conduction band and forbidden band of the well layer adjacent to the second barrier layer respectively
Data Source
AI summary
A multi-quantum well structure includes two first barrier layers, two well layers sandwiched between the two first barrier layers, and a doped second barrier layer sandwiched between the two well layers. The second barrier layer has its conduction band and forbidden band gradually transiting to those of one of the well layers, and a dopant concentration of the second barrier layer gradually changes along a direction from one well layer to the other. The invention also relates to a light emitting diode structure having the multi-quantum well structure.