Nitride Light-Emitting Structure With Strain Relaxation for Long Wavelengths
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Solution Overview
Problem
Nitride-based semiconductor light-emitting devices face challenges due to crystal defects caused by lattice constant mismatches and thermal expansion differences between the growth substrate and the nitride-based semiconductor, leading to reduced light-emitting efficiency, especially when increasing the Indium composition for longer wavelengths.
Innovation Solution
Incorporating a strain relaxation layer with a superlattice buffer structure and an AlGaN layer having a protrusion with a decreasing horizontal cross-sectional area between the semiconductor layers, which suppresses dislocation propagation and reduces crystal defects in the light-emitting layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the Indium composition in the InGaN layer is increased to implement long wavelength emission, then the light emission wavelength is extended, but the lattice constant mismatch increases causing more crystal defects and reduced light emitting efficiency
Solution Approach 1:
The patent introduces a strain relaxation layer as an intermediary between the substrate and the InGaN light-emitting layer. This layer mediates the lattice mismatch stress by gradually transitioning from the substrate lattice constant to the InGaN layer lattice constant, preventing direct stress transmission that would cause crystal defects. The strain relaxation layer acts as a buffer zone that decouples the conflicting lattice constants, allowing high Indium composition for long wavelength emission without proportionally increasing defects.
2Reliability
If a strain relaxation layer is added to reduce crystal defects, then the light emitting efficiency is improved, but the device structure becomes more complex
Solution Approach 1:
The patent segments the semiconductor structure into distinct functional layers: substrate, strain relaxation layer, and InGaN light-emitting layer. The strain relaxation layer itself is segmented into multiple sub-layers with progressively increasing Indium composition, creating a gradient structure. This segmentation allows each layer to perform its specific function optimally while managing the overall complexity through modular design.
Solution Approach 2:
The patent changes the compositional parameter of the strain relaxation layer by using multiple layers with progressively increasing Indium content. This parameter gradient approach allows the strain relaxation layer to adaptively manage lattice mismatch stress at each interface, reducing defect propagation while maintaining structural integrity. The gradual parameter change prevents abrupt transitions that would generate additional defects.
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-emission efficiency by minimizing crystal defects and supporting the use of higher Indium compositions for longer wavelengths, thereby improving the performance of nitride-based semiconductor light-emitting devices across various color ranges.
Implementation Method 1
the AlGaN layer may be configured to suppress propagation of dislocations from the V-shaped pits toward the light-emitting layer
Implementation Method 2
Such crystal defects may occur due to a mismatch in lattice constants or a difference in thermal expansion coefficients between a growth substrate and a nitride-based semiconductor grown thereon
Implementation Method 3
heat energy rather than light energy may be emitted through the crystal defects when electrons and holes are coupled together
Data Source
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AI summary
A nitride-based semiconductor light-emitting device, including a first semiconductor layer, wherein the first semiconductor layer is nitride-based and has a first conductivity type; a light-emitting layer provided on the first semiconductor layer, wherein the light-emitting layer may include a nitride-based semiconductor including Indium (In); a second semiconductor layer provided on the light-emitting layer, wherein the second semiconductor layer is nitride-based and has a second conductivity type; and a strain relaxation layer provided between the first semiconductor layer and the light-emitting layer, and including an AlGaN layer having a protrusion whose horizontal cross-section area decreases as the protrusion extends in a vertical direction from the second semiconductor layer to the first semiconductor layer.