Nano-Structured Light Extraction Layer for High-Contrast MicroLED Pixels
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Solution Overview
Problem
Existing semiconductor light-emitting devices face challenges in maintaining adequate internal quantum efficiency and light extraction as pixel sizes decrease, particularly for miniLED and microLED arrays, due to non-radiative recombination at etched sidewalls and inefficient light extraction from small pixels.
Innovation Solution
A semiconductor light-emitting device with first and second doped semiconductor layers, a junction or active layer, and a set of nanostructured optical elements that redirect laterally propagating light to exit through a second semiconductor layer, using composite electrical contacts with transparent dielectric layers and vias to enhance light extraction and maintain pixel contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pixel sizes are decreased to increase device density, then device integration is improved, but light extraction efficiency deteriorates due to non-radiative recombination at etched sidewalls
Solution Approach 1:
The patent extracts and removes the harmful etched sidewalls from the pixel structure by using a planar epitaxial growth method that eliminates the need for lateral patterning and etching steps, thereby removing the source of non-radiative recombination while maintaining small pixel dimensions
Solution Approach 2:
The patent replaces the mechanical etching process with a chemical epitaxial growth process that forms pixels laterally through selective growth rather than removal of material, substituting a process that creates harmful surfaces with one that maintains smooth, radiative surfaces
2Productivity
If pixel sizes are decreased to increase device density, then device integration is improved, but light extraction efficiency deteriorates due to inefficient light extraction from small pixels
Solution Approach 1:
The patent addresses the light extraction problem by introducing vertical dimensionality through controlled epitaxial growth that creates depth variation in the pixel structures, enabling light extraction enhancement without increasing lateral pixel dimensions
3Reliability
If conventional electrical contacts are used, then electrical connection is achieved, but light extraction is reduced due to blocking of laterally propagating light
Solution Approach 1:
The patent introduces an intermediary optical cavity structure between the electrical contacts and the light-emitting region that allows electrical connections to be made while enabling laterally propagating light to reflect off the cavity walls and exit through the pixel aperture, thus mediating between electrical and optical requirements
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 light extraction efficiency and internal quantum efficiency while maintaining pixel contrast, even at small pixel sizes, by reducing the number of laterally propagating modes and optimizing nanostructured optical elements for redirected light emission.
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
Data Source
Figure 1~2B
Figure 3A~3B
Figure 4A
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.