Patterned Substrate LED for Uniform Current Distribution
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Solution Overview
Problem
Conventional light-emitting diodes (LEDs) face challenges in achieving high external quantum efficiency due to lattice-mismatch-induced crystal defects and inefficient current spreading, which affect the uniformity and brightness of light emission.
Innovation Solution
A light-emitting device with a patterned substrate featuring a combination of first and second patterns, where the light-emitting stack is grown on a single-crystalline buffer layer with a rough surface to reduce stress and enhance epitaxial growth, and a current spreading layer to ensure even current distribution, optimizing the fill factor and light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional flat substrate is used for LED growth, then the manufacturing process is simple, but lattice-mismatch-induced crystal defects occur and external quantum efficiency is reduced
Solution Approach 1:
The substrate surface is segmented into multiple patterns with different feature lengths (first patterns with larger feature length and second patterns with smaller feature length). This segmentation allows different regions to serve different functions: larger patterns provide stable crystal growth areas while smaller patterns help distribute current more evenly, thereby reducing crystal defects and improving external quantum efficiency without requiring complete substrate replacement
Solution Approach 2:
Different regions of the substrate surface are given different local qualities through the patterned structure. The first patterns with larger feature lengths provide areas optimized for crystal growth stability, while the second patterns with smaller feature lengths are optimized for current spreading. This local differentiation allows each region to contribute optimally to reducing crystal defects and enhancing overall device performance
2Manufacturing precision
If uniform current distribution is desired across the LED, then a current spreading layer with specific patterns is needed, but this increases manufacturing complexity
Solution Approach 1:
The current spreading layer incorporates patterns that segment the current flow paths. By creating multiple current injection channels through the patterned structure, the current is naturally distributed more uniformly across the active region. This segmentation approach achieves precise current control without requiring complex external current management systems
Solution Approach 2:
The patterned substrate structure and current spreading layer are combined into an integrated design. The patterns on the substrate work synergistically with the current spreading layer patterns to achieve uniform current distribution. This merging of functions reduces the number of separate manufacturing steps while maintaining high manufacturing precision for current uniformity
3Reliability
If the substrate surface is made rough to reduce stress and enhance epitaxial growth, then crystal quality improves, but the manufacturing process becomes more complex
Solution Approach 1:
The substrate surface is pre-treated with a specific rough pattern structure before epitaxial growth begins. This preliminary surface preparation creates nucleation sites that promote stress reduction and enhance the quality of subsequent crystal growth. By performing this surface modification in advance, the complex roughening process is decoupled from the growth process, making overall manufacturing more manageable
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 solution results in improved external quantum efficiency and enhanced light emission uniformity by minimizing crystal defects and optimizing current distribution, leading to higher fill factors and brighter light output.
Implementation Method 1
a p-type semiconductor layer, an n-type semiconductor layer, and an active region formed between the p-type semiconductor layer and the n-type semiconductor layer for emitting light under the principle of transforming electrical energy to optical energy by injecting electrons and holes through the n-type semiconductor layer and the p-type semiconductor layer respectively to the active region to perform radiative combination and emit light
Data Source
AI summary
A semiconductor device comprises a substrate comprising a surface area having a plurality of patterns therein, wherein the plurality of patterns comprises a plurality of first patterns and a plurality of second patterns; and a light-emitting stack formed on the substrate; wherein each of the first patterns comprises a first feature length and each of the second patterns comprises a second feature length smaller than the first feature length, and wherein, in a square area of 30 microns by 30 microns chosen from the surface area, an amount of the plurality of the first patterns is more than that of the plurality of the second patterns.