Nitride LED Epitaxial Structure for Low Bowing and Defect Control
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Solution Overview
Problem
Conventional light-emitting diode (LED) structures face issues such as cracks, warpage, bowing, fractures, and breakages due to differing thermal expansion coefficients of materials, affecting luminous efficiency.
Innovation Solution
A light-emitting element structure comprising a substrate, nucleation layer, buffer layer, first nitride layer, second nitride layer, first semiconductor layer, light-emitting layer, and second semiconductor layer, where the first nitride layer has a smaller film thickness than the second nitride layer, with a dislocation defect density of the second nitride layer less than or equal to 3×10^9 cm^-2, and an absolute bowing (BOW) value between -10 and 10 μm, reducing defects and enhancing luminous efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional LED structure with different material layers is used, then light emission function is achieved, but thermal expansion coefficient differences cause cracks, warpage, and fractures
Solution Approach 1:
The patent introduces a buffer layer as an intermediary between the substrate and the nitride layers. This buffer layer mediates the thermal expansion coefficient differences between the substrate and the light-emitting layers, reducing thermal stress and preventing cracks and warpage while maintaining the light emission function.
Solution Approach 2:
The patent changes the physical parameters of the intermediate layers by controlling their thickness (first nitride layer thinner than second nitride layer) and material composition. These parameter changes optimize the stress distribution and reduce thermal expansion coefficient mismatches, thereby improving structural reliability.
2Illumination intensity
If multiple epitaxial layers with different materials are stacked, then light emission is enabled, but dislocation defects and bowing occur
Solution Approach 1:
The patent segments the epitaxial structure into multiple functional layers with different thicknesses and compositions (nucleation layer, buffer layer, first and second nitride layers with different thicknesses, semiconductor layers). This segmentation allows each layer to address specific issues: the nucleation layer initiates growth, the buffer layer reduces dislocations, and the varying nitride layer thicknesses control stress and bowing, collectively improving epitaxial quality while maintaining luminous efficiency.
Solution Approach 2:
The patent applies local quality by making the first nitride layer thinner than the second nitride layer. This non-uniform thickness distribution creates different local properties within the nitride structure, allowing optimization of both dislocation reduction and stress control in different regions, thereby improving overall epitaxial quality without sacrificing light emission 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
The structure effectively reduces defects like cracks and warpage, improving the epitaxial quality and luminous efficiency of the light-emitting element by controlling dislocation defect density and bowing, resulting in improved performance compared to conventional structures.
Implementation Method 1
a light-emitting layer located between the p-type semiconductor layer and the n-type semiconductor layer... adapted to emit light when electrons and holes recombine
Data Source
AI summary
A light-emitting element structure includes a substrate, a nucleation layer located above the substrate, a buffer layer located above the nucleation layer, a first nitride layer located above the buffer layer and being in contact with the buffer layer, a second nitride layer located above the first nitride layer and being in contact with the first nitride layer, a first semiconductor layer located above the second nitride layer, a light-emitting layer, and a second semiconductor layer located above the light-emitting layer. A film thickness of the first nitride layer is smaller than a film thickness of the second nitride layer. A dislocation defect density of the second nitride layer is smaller than or equal to 3×109 cm−2. The light-emitting layer is located above the first semiconductor layer and is adapted to emit light when electrons and holes recombine.