Light Emitting Element Sidewall Electrode Extraction
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Solution Overview
Problem
Light emitting elements, such as LEDs, face low light extraction efficiency due to the difference in optical refractive indices between the element and surrounding materials, resulting in a significant amount of light being trapped inside rather than emitted externally.
Innovation Solution
A light emitting element design featuring a substrate with a light emitting structure comprising a first and second conductive layer, where the second electrode is connected to the sidewall of the substrate and the light emitting structure, allowing light to be reflected and extracted more efficiently, and a fabrication method that includes forming a groove in the substrate and stacking the conductive and light emitting layers with the second electrode formed conformally along the profile of the light emitting structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If light emitting element uses conventional planar structure with electrodes only on top surface, then device complexity is low and ease of manufacture is high, but light extraction efficiency is poor due to total internal reflection at planar interfaces
Solution Approach 1:
The patent extends the second electrode from the top surface down through the sidewalls to the bottom surface of the light emitting structure, creating a three-dimensional electrode configuration. This vertical extension into the depth dimension allows the electrode to extract light that would otherwise be trapped by total internal reflection at the planar top and bottom interfaces, significantly improving light extraction efficiency without requiring complex lateral structures
Solution Approach 2:
The patent introduces a reflective layer between the second electrode and the light emitting structure. This intermediary reflective layer redirects light that strikes the electrode at oblique angles back toward the light emitting structure, preventing light loss and enabling multiple extraction opportunities. The reflective layer acts as a mediator that converts potentially lost light into extractable light, improving overall extraction efficiency while maintaining electrode structural simplicity
2Loss of energy
If light emitting element uses conventional top-only electrode configuration, then manufacturing process is simple, but light extraction efficiency is limited by critical angle constraints at planar interfaces
Solution Approach 1:
The second electrode is formed to extend vertically from the top surface through the sidewalls to the bottom surface, utilizing the depth dimension of the light emitting structure. This vertical configuration allows the electrode to intercept and extract light at multiple depths and angles, overcoming the critical angle limitations of planar interfaces. The extended electrode structure can be fabricated using standard semiconductor processing techniques such as etching and electrodeposition, maintaining ease of manufacture while dramatically improving light extraction efficiency
Solution Approach 2:
The patent changes the geometric parameters of the electrode structure by extending it vertically through the light emitting structure rather than keeping it confined to the top surface. This parameter change transforms the electrode from a two-dimensional surface element to a three-dimensional volume-filling structure, enabling it to interact with light across the entire depth of the device and extract light that would otherwise be trapped by total internal reflection
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 design significantly enhances light extraction efficiency by allowing more light to exit the element, improving its external light emission and reducing internal reflection.
Implementation Method 1
a second electrode which is electrically connected with the second conductive layer and separated apart from the first electrode. At least a part of the second electrode is connected from a top of the light emitting structure, through a sidewall of the light emitting structure, and to a sidewall of the substrate
Data Source
AI summary
Provided is a light emitting element, a light emitting device including the same, and fabrication methods of the light emitting element and light emitting device. The light emitting device comprises a substrate, a light emitting structure including a first conductive layer of a first conductivity type, a light emitting layer, and a second conductive layer of a second conductivity type which are sequentially stacked, a first electrode which is electrically connected with the first conductive layer; and a second electrode which is electrically connected with the second conductive layer and separated apart from the first electrode, wherein at least a part of the second electrode is connected from a top of the light emitting structure, through a sidewall of the light emitting structure, and to a sidewall of the substrate.