Nano-Structured LED Light Extraction Layer for High Pixel Contrast
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Solution Overview
Problem
Conventional light-emitting diodes (LEDs) face challenges in achieving high internal quantum efficiency and light extraction, especially at small pixel sizes, due to non-radiative carrier recombination at defect sites and difficult light extraction as pixel size decreases, which degrades contrast and emission efficiency.
Innovation Solution
A semiconductor light-emitting device with first and second doped semiconductor layers and a junction or active layer, featuring multiple nanostructured optical elements that redirect laterally propagating light to exit through the second semiconductor layer, reducing the number of supported optical modes and optimizing nanostructured elements for improved extraction efficiency and contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pixel size is decreased to increase device density, then device integration is improved, but light extraction efficiency deteriorates and contrast between adjacent pixels degrades
Solution Approach 1:
The patent introduces a vertical dimension solution by placing nanostructured optical elements on top of the LED active region. These elements manipulate light in the vertical dimension through mode conversion, transforming laterally propagating modes into vertically exiting modes. This dimensional approach to light management enables efficient light extraction from mini- and microLEDs without requiring larger pixel areas, thereby resolving the contradiction between high device density and light extraction efficiency.
Solution Approach 2:
The patent employs parameter changes by modifying the optical mode distribution through nanostructured elements. By converting optical modes from lateral propagation to vertical emission, the effective extraction parameter is changed. This parameter transformation allows small pixel sizes to maintain high light extraction efficiency, addressing the contradiction between device integration density and energy loss through improved light extraction.
2Productivity
If pixel size is decreased to increase device density, then device integration is improved, but contrast between adjacent pixels deteriorates
Solution Approach 1:
The nanostructured optical elements operate in the vertical dimension to redirect laterally propagating light modes into vertical emission modes. This dimensional manipulation confines light extraction to the vertical direction above each pixel, preventing lateral light leakage into adjacent pixels. Consequently, high pixel contrast is maintained even at high device densities, resolving the contradiction between integration density and measurement precision (pixel contrast).
3Device complexity
If conventional light extraction methods are used in mini- and microLEDs, then device structure is simple, but light extraction efficiency deteriorates due to total internal reflection
Solution Approach 1:
The patent introduces nanostructured optical elements as intermediary components between the LED active region and the external environment. These elements act as mediators that facilitate light extraction by converting optical modes and enabling light to overcome total internal reflection at the semiconductor-air interface. This intermediary approach improves light extraction efficiency while maintaining relatively simple device structure, resolving the contradiction between structural simplicity and energy loss.
Solution Approach 2:
The patent replaces conventional mechanical or geometric light extraction methods (such as surface texturing or patterned substrates) with nanoscale optical elements that manipulate light through mode conversion. This substitution achieves superior light extraction efficiency by addressing the fundamental optical limitation of total internal reflection, while maintaining device structural simplicity. The nanoscale elements provide an elegant solution that trades minimal structural complexity for significant improvements in light extraction.
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 enhances internal quantum efficiency, light extraction, and contrast between adjacent pixels, maintaining desirable emission efficiency even at small pixel sizes, while simplifying fabrication by eliminating the need for inter-pixel trenches.
Implementation Method 1
a set of multiple nanostructured optical elements arranged, at the first surface of the first semiconductor layer or at a surface of the second semiconductor layer opposite the first semiconductor layer, so as to redirect at least a portion of light (at the nominal emission vacuum wavelength λ0) propagating laterally in one or more selected optical modes supported by the first and second semiconductor layers to exit the device through the second semiconductor layer
Implementation Method 2
first and second doped semiconductor layers that are arranged for emitting light at a nominal emission vacuum wavelength λ0 resulting from carrier recombination at a junction or active layer between the first and second semiconductor layers
Data Source
AI summary
A semiconductor light-emitting device includes a junction or active layer between doped semiconductor layers coextensive over a contiguous device area, corresponding sets of electrical contacts connected to the semiconductor layers, and multiple nanostructured optical elements at a surface of one semiconductor layer opposite the other semiconductor layer. Composite electrical contacts of one set include a conductive layer, a transparent dielectric layer between the conductive and semiconductor layers, and vias through the dielectric layer connecting the conductive and semiconductor layers. The nanostructured elements redirect light, propagating laterally in optical modes supported by the semiconductor layers, to exit the device. The composite electrical contacts can be independent and define independently addressable pixel areas of the device. The nanostructured elements and thin semiconductor layers can yield high contrast between adjacent pixel areas without trenches between them. A drive circuit can provide drive current that differs among pixel areas.