Gradient Quantum Well Structure for Higher Light Extraction
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Solution Overview
Problem
Conventional nitride semiconductors face issues with lattice mismatch and thermal mismatch, leading to high defect density, polarization effects, and low light-emitting efficiency in semiconductor light-emitting devices.
Innovation Solution
A semiconductor light-emitting device is designed with a substrate, a Negative-type semiconductor, a quantum well with a periodic structure of well and barrier layers, an electron-blocking layer, and a Positive-type semiconductor, where the dielectric constants, refractive indexes, forbidden bandwidths, and electron effective masses are distributed in a gradient to improve light reflection, refraction, and extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional nitride semiconductors are used with common substrate growth manners, then the device structure is simple and easy to manufacture, but large lattice mismatch and thermal mismatch occur, leading to high defect density and low light-emitting efficiency
Solution Approach 1:
The patent divides the semiconductor structure into multiple segments including substrate, buffer layer, multiple quantum wells, electron-blocking layer, and contact layers. This segmentation allows each layer to be optimized independently for lattice matching, reducing overall defect density while maintaining manufacturability through standardized growth processes for each segment.
Solution Approach 2:
The patent implements local quality optimization by creating specific buffer layer compositions and graded structures at critical interfaces. The buffer layer uses localized compositional gradients to gradually transition between lattice constants, reducing mismatch effects only where needed at substrate interfaces while keeping other regions simple.
2Manufacturing precision
If conventional nitride semiconductors are used, then the device structure is simple, but thermal mismatch occurs leading to high defect density and reduced light-emitting efficiency
Solution Approach 1:
The patent changes material parameters by selecting specific semiconductor compounds with matched thermal expansion coefficients. The buffer layer and quantum well layers use compositional variations to achieve thermal parameter matching, reducing thermally-induced defects without requiring complex device architectures.
3Manufacturing precision
If conventional nitride semiconductors are used, then the device structure is simple and easy to manufacture, but polarization effects increase, reducing light-emitting efficiency
Solution Approach 1:
The patent introduces asymmetric quantum well structures with different barrier and well layer thicknesses and compositions. This asymmetry allows control over polarization field distribution, reducing net polarization effects that would otherwise reduce light-emitting efficiency in conventional symmetric structures.
4Manufacturing precision
If conventional nitride semiconductors are used, then the device structure is simple, but hole ionization efficiency is low, resulting in low hole concentration and reduced light-emitting efficiency
Solution Approach 1:
The patent changes band structure parameters by adjusting quantum well composition and thickness to optimize hole ionization energies. The electron-blocking layer uses specific material parameters to create favorable band alignment that enhances hole injection efficiency into quantum wells, increasing hole concentration without complex device modifications.
5Manufacturing precision
If conventional nitride semiconductor structure is used, then the device structure is simple, but strong spontaneous polarization and piezoelectric polarization form intrinsic polarization fields, causing quantum confinement Stark effect and spatial separation of electron-hole wave function, reducing radiative recombination efficiency
Solution Approach 1:
The patent employs asymmetric quantum well designs where barrier and well layer thicknesses and compositions are deliberately unbalanced. This asymmetry modifies the internal electric field distribution, reducing the quantum confinement Stark effect and minimizing spatial separation of electron and hole wave functions, thereby enhancing radiative recombination efficiency.
6Manufacturing precision
If conventional nitride semiconductor structure is used, then the device structure is simple, but refractive index is greater than air, resulting in small total reflection angle and low light extraction efficiency
Solution Approach 1:
The patent segments the optical path by introducing multiple layers with different refractive indices, including distributed Bragg reflectors and extraction enhancement layers. This segmentation creates multiple opportunities for light extraction at different interfaces, increasing overall light extraction efficiency from the semiconductor device.
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 gradient distribution of optical parameters enhances light extraction efficiency from 40% to 95%, increases the light-emitting angle, and improves the crystal quality and interface quality of the quantum well, thereby enhancing the overall efficiency and aging resistance of the semiconductor light-emitting device.
Implementation Method 1
the dielectric constants, refractive indexes, forbidden bandwidths, and electron effective masses are distributed in a gradient to improve light reflection, refraction, and extraction efficiency
Implementation Method 2
the dielectric constants, refractive indexes, forbidden bandwidths, and electron effective masses are distributed in a gradient to improve light reflection, refraction, and extraction efficiency
Implementation Method 3
A semiconductor light-emitting device is designed with a substrate, a Negative-type semiconductor, a quantum well with a periodic structure of well and barrier layers, an electron-blocking layer, and a Positive-type semiconductor
Implementation Method 4
The gradient distribution of optical parameters enhances light extraction efficiency from 40% to 95%, increases the light-emitting angle
Data Source
AI summary
Semiconductor light-emitting devices are provided, which includes a substrate, a Negative-type semiconductor, a quantum well, an electron-blocking layer, and a Positive-type semiconductor arranged in a sequential stack. The quantum well includes a first quantum well, a second quantum well, and a third quantum well. Optical parameters of the first quantum well, the second quantum well, and the third quantum well are distributed in a gradient in at least one direction. The quantum well includes a periodic structure consisting of a well layer and a barrier layer. A coefficient of thermal expansion of the well layer is smaller than or equal to that of the barrier layer. An elastic coefficient of the well layer is smaller than or equal to that of the barrier layer. A lattice constant of the well layer is greater than or equal to that of the barrier layer. A coefficient of spontaneous polarization of the well layer is smaller than or equal to that of spontaneous polarization of the barrier layer.