Cone-Structured Light Extraction Surface for Deep UV LEDs
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Solution Overview
Problem
The external quantum efficiency of deep ultraviolet light output from semiconductor light emitting devices is low, particularly for shorter wavelengths, due to total reflection at the light extraction surface, which limits their effectiveness.
Innovation Solution
A semiconductor light emitting device with a concave-convex structure featuring cone-shaped parts on the light extraction surface, where the angle of inclination varies in stages, and the height of the second portion with a smaller angle is larger than the first portion, significantly improving light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional flat light extraction surface is used, then the device structure is simple, but the external quantum efficiency is low due to total reflection of light
Solution Approach 1:
The patent applies curvature by forming cone-shaped parts on the light extraction surface instead of using a flat surface. The conical geometry with specific inclination angles (first angle and second angle) creates curved interfaces that reduce total reflection of deep ultraviolet light, thereby improving light extraction efficiency while maintaining a relatively simple overall device structure
Solution Approach 2:
The patent implements local quality by creating a multi-layered concave-convex structure where different portions of the light extraction surface have different properties. The first portion has a first inclination angle and the second portion has a second inclination angle, allowing each region to be optimized for light extraction while maintaining structural integrity
2Loss of energy
If the light extraction surface is modified with concave-convex structures, then light extraction efficiency is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies segmentation by dividing the light extraction surface into distinct conical structures with different inclination angles (first portion and second portion). This segmented approach allows each segment to be optimized independently for light extraction while the overall pattern can be manufactured using standard photolithography and etching processes
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 described structure enhances light extraction efficiency by inhibiting total reflection and increasing the proportion of light output, achieving higher efficiency compared to conventional designs.
Implementation Method 1
the external quantum efficiency of deep ultraviolet light output via the light extraction surface of the substrate of a deep ultraviolet light emitting device is as low as several %... the concave-convex structure provided by forming a plurality of cone-shaped parts in an array on the light extraction surface inhibits total reflection of light occurring inside the light extraction surface
Data Source
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AI summary
A semiconductor light emitting device 10 includes a light extraction layer having a light extraction surface 22b. A plurality of cone-shaped parts 52 formed in an array are provided on the light extraction surface 22b. The cone-shaped part 52 has a first portion 53 having a first angle of inclination of a side surface and a second portion 54 having a second angle of inclination of a side surface smaller than the first angle. The second portion 54 is closer to an apex of the cone-shaped part than the first portion 53 and has a larger height than the first portion 53.