Patterned Sapphire Substrate Concave Regions Light Extraction
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Solution Overview
Problem
Existing patterned sapphire substrates face challenges in optimizing light extraction efficiency due to the width of pattern bottoms and spacing between patterns, which affects the dislocation density and lattice quality of epitaxial structures, leading to suboptimal light reflection and extraction in light-emitting diodes.
Innovation Solution
A patterned sapphire substrate with a design featuring a plurality of interspaced patterns having concave regions between adjacent side surfaces, where the depth and width of the concave regions decrease from the top to the bottom, and a method involving wet etching with a mask layer to increase the bottom width and light reflection area, while maintaining constant pitch, is employed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the pattern bottom width is increased to enlarge light reflection area, then light extraction efficiency is improved, but the space between adjacent patterns decreases leading to increased defects in epitaxial layer
Solution Approach 1:
The patent applies local quality by creating concave regions at specific locations between adjacent pattern side surfaces. These concave regions are positioned locally to maximize light reflection area without reducing the spacing between pattern bases. The concave regions have different depths and widths that gradually decrease from top to bottom, providing localized light extraction enhancement while maintaining overall pattern spacing for healthy epitaxial growth.
Solution Approach 2:
The patent transitions from a two-dimensional pattern surface to a three-dimensional structure by introducing concave regions between adjacent side surfaces. This dimensional change creates additional light reflection surfaces within the vertical space between patterns, effectively increasing light extraction area without occupying additional horizontal space that would reduce pattern spacing.
2Productivity
If the space between patterns is reduced to increase pattern density, then substrate light extraction efficiency is improved, but the internal defects in epitaxial layer increase
Solution Approach 1:
The patent resolves this contradiction by utilizing the vertical dimension to increase light extraction functionality. The concave regions between adjacent side surfaces create additional light reflection surfaces without requiring reduced horizontal spacing between patterns. This allows maintaining adequate pattern spacing for defect-free epitaxial growth while achieving high light extraction efficiency through three-dimensional light scattering and reflection paths.
3Illumination intensity
If the pattern surface area is increased to enhance light reflection, then light extraction efficiency is improved, but the complexity of pattern structure increases
Solution Approach 1:
The patent implements local quality by introducing concave regions only in specific areas between adjacent side surfaces, rather than modifying the entire pattern structure. This localized approach increases light reflection area while minimizing structural complexity. The concave regions are formed with simple geometric features (inclined surfaces meeting at specific angles) that can be achieved through standard fabrication 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
This design enhances light extraction efficiency by increasing the light reflection area and reducing defects in the epitaxial layer, resulting in improved performance of light-emitting diodes.
Implementation Method 1
the first surface of the substrate is formed by arranging a plurality of interspaced patterns... formed via photoetching and etching
Implementation Method 2
etching the first surface of the sapphire plain substrate via wet etching to form a plurality of periodically-arranged interspaced patterns
Implementation Method 3
the pattern structure increases light scattering and changes light route of the light-emitting diode, thus optimizing light extraction chance
Implementation Method 4
enlarging reflection area of the pattern surface of the patterned substrate... improve light reflection by the substrate
Data Source
AI summary
A patterned sapphire substrate has a first surface and a second surface opposite to each other, in which, the first surface of the substrate is formed by arranging a plurality of interspaced patterns, wherein, the patterns have a top surface, a bottom surface and a plurality of side surfaces and at least one concave region sandwiched between the adjacent side surfaces and the top surface, where, depth and width of the concave region gradually decrease from the top to the bottom of the pattern. The concave region on the pattern surface of the patterned sapphire substrate enlarges light reflection area, thus improving light extraction efficiency of the patterned sapphire substrate.