Optical Substrate Concave-Convex Structure for LED Efficiency
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Solution Overview
Problem
Conventional semiconductor light-emitting elements, such as LEDs, face challenges in achieving optimal light extraction efficiency and internal quantum efficiency due to dislocation defects and waveguide modes caused by lattice mismatch and refractive index differences, leading to tradeoffs in enhancing electron injection efficiency and light extraction efficiency.
Innovation Solution
An optical substrate with a concave-convex structure is developed, featuring a specific arrangement of convex and concave portions with varying heights and depths, and an average interval that optimizes light scattering, reducing dislocation density and enhancing ohmic contact, thereby improving internal quantum efficiency and light extraction efficiency simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single crystal substrate (sapphire or SiC) is used, then the structural integrity and manufacturing process are simple, but dislocation defects are generated due to lattice mismatch and light forms waveguide modes due to refractive index differences, reducing light extraction efficiency
Solution Approach 1:
The substrate surface is segmented into multiple convex portions with different heights and intervals, creating a multi-scale concave-convex structure. This segmentation disrupts the continuous waveguide mode and disperses dislocation defects by dividing the uniform surface into heterogeneous regions with varying light scattering properties.
Solution Approach 2:
Different regions of the substrate surface are given different local qualities through varying convex portion heights (first height h1 and second height h2) and intervals. This creates zones with different light scattering strengths and dislocation dispersion effects, optimizing both light extraction efficiency and defect reduction in specific areas.
2Reliability
If the average interval between convex portions is reduced to disperse dislocations, then internal quantum efficiency improves, but the light scattering effect for disrupting waveguide modes may be reduced
Solution Approach 1:
The problem is solved by adding a vertical dimension to the convex portions with two different heights (h1 and h2). This multi-level structure creates additional light scattering pathways in the vertical direction while maintaining small horizontal intervals for dislocation dispersion, thereby preserving both internal quantum efficiency and light scattering effectiveness.
Solution Approach 2:
The substrate surface creates a composite structure with convex portions of different heights forming a heterogeneous landscape. This composite morphology combines the benefits of fine spacing for dislocation control with varied height profiles for enhanced light scattering, achieving both improved internal quantum efficiency and maintained light extraction capability.
3Reliability
If a concave-convex structure is formed on the substrate surface, then light extraction efficiency and dislocation dispersion improve, but the manufacturing complexity and precision requirements increase
Solution Approach 1:
The invention controls complexity by defining specific parameter ranges: average interval Pave between 1.5-10 μm, convex portion heights h1 and h2 within measurable ranges, and probability Z between 0.1-0.5. These quantified parameters provide clear manufacturing targets while achieving the dual benefits of light extraction improvement and dislocation dispersion without excessive complexity.
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 concave-convex structure effectively disperses dislocations, increases light extraction efficiency, and enhances electron injection efficiency, resulting in improved external quantum efficiency of LED elements by disturbing waveguide modes and increasing the specific surface area for better ohmic contact.
Implementation Method 1
a concave-convex structure is provided in a single crystal substrate to change a light waveguide direction in a semiconductor crystal layer and thus a light extraction efficiency is increased
Data Source
Figure 1~2
Figure 3~4B
Figure 5
AI summary
In an optical substrate (1), a concave-convex structure (12) including a plurality of independent convex portions (131 to 134) and concave portions (14) provided between the convex portions (131 to 134) is provided in a surface. The average interval Pave between the adjacent convex portions (131 to 134) in the concave-convex structure (12) satisfies 50 nm ≤ Pave ≤ 1500 nm, and the convex portion (133) having a convex portion height hn satisfying 0.6 h ≥ hn ≥ 0 h for the average convex portion height Have is present with a probability Z satisfying 1/10000 ≤ Z ≤ 1/5. When the optical substrate (1) is used in a semiconductor light-emitting element, dislocations in a semiconductor layer are dispersed to reduce the dislocation density, and thus internal quantum efficiency IQE is improved, and a waveguide mode is removed by light scattering and thus the light the extraction efficiency LEE is increased, with the result that the efficiency of light emission of the semiconductor light-emitting element is enhanced.