Patterned Substrate for Nitride Semiconductor Light Extraction
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Solution Overview
Problem
Conventional semiconductor light emitting devices face challenges in maximizing light extraction efficiency due to total internal reflection and limited surface area of the active layer, leading to suboptimal quantum efficiency.
Innovation Solution
A semiconductor light emitting device with a patterned substrate featuring locally irregular convex portions of varying shapes and sizes, which changes the growth mode of nitride semiconductors to increase the surface area of the active layer and enhance light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a flat substrate is used, then the manufacturing process is simple, but the light extraction efficiency is low due to total internal reflection
Solution Approach 1:
The patent applies curvature by forming convex portions on the substrate surface instead of using a flat surface. These convex portions have curved surfaces that change the incident angles of light, enabling light extraction even when the incident angle exceeds the critical angle for total internal reflection. This resolves the contradiction by maintaining manufacturing simplicity while significantly improving light extraction efficiency through geometric curvature modification.
2Ease of manufacture
If a regular pattern is formed on the substrate, then the manufacturing process is straightforward, but the nitride semiconductor growth is non-uniform leading to manufacturing difficulties
Solution Approach 1:
The patent applies local quality by making the convex portions have different sizes, shapes, and spacing arrangements rather than using a uniform regular pattern. This local variation in pattern characteristics allows different regions of the substrate to provide optimal growth conditions for nitride semiconductor formation, achieving uniform and high-quality semiconductor growth while maintaining pattern formation simplicity.
3Loss of energy
If the active layer surface area is increased, then the internal quantum efficiency is enhanced, but the device structure becomes more complex
Solution Approach 1:
The patent applies dimensionality change by transitioning from a two-dimensional flat active layer to a three-dimensional structure with convex portions. This vertical dimensionality addition increases the effective surface area of the active layer without requiring lateral expansion, thereby enhancing internal quantum efficiency while avoiding increased device footprint and structural 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 patterned substrate design increases internal and external quantum efficiency by altering the growth mode and light extraction pathways, resulting in improved optical output and efficiency.
Implementation Method 1
nitride semiconductors begin to grow from a flat surface of the square convex portions and a bottom surface of the substrate
Implementation Method 2
light generated from the nitride light emitting device, when having an incident angle greater than a critical angle due to differences in refractivity, undergoes total internal reflection and thus cannot be extracted outward
Data Source
AI summary
There is provided a semiconductor light emitting device having a patterned substrate and a manufacturing method of the same. The semiconductor light emitting device includes a substrate; a first conductivity type nitride semiconductor layer, an active layer and a second conductivity type nitride semiconductor layer sequentially formed on the substrate, wherein the substrate is provided on a surface thereof with a pattern having a plurality of convex portions, wherein out of the plurality of convex portions of the pattern, a distance between a first convex portion and an adjacent one of the convex portions is different from a distance between a second convex portion and an adjacent one of the convex portions.