Reflective LED Electrode Structure for Lower Light Absorption
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Solution Overview
Problem
Contemporary light emitting diodes (LEDs) suffer from inefficiency due to internal absorption of light, limiting their brightness and suitability for applications beyond indicator use, such as general illumination.
Innovation Solution
A reflective electrode structure is implemented, featuring a metal electrode with a thick, optically transmissive dielectric layer and DBR pairs, which enhances light reflection and reduces absorption, allowing more light to be extracted from the LED.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional electrode structure is used in LEDs, then the device complexity is low, but light absorption increases and light extraction efficiency decreases
Solution Approach 1:
A dielectric layer is introduced as an intermediary between the metal electrode and the semiconductor material. This dielectric layer serves as a mediator that reflects light away from the electrode, preventing direct absorption of light by the metal while still allowing the electrode to perform its electrical function. The dielectric layer thus mediates between the conflicting requirements of electrical conductivity and optical transparency/reflectivity.
Solution Approach 2:
The electrode structure is transformed from a simple metal layer into a composite structure consisting of multiple layers: metal electrode, dielectric layer, and optionally additional functional layers. This composite structure combines the electrical conductivity of metal with the optical properties of dielectric materials, achieving both low light absorption and good electrical performance.
2Productivity
If the electrode structure is modified to reduce light absorption, then light extraction efficiency improves, but the manufacturing process becomes more complex
Solution Approach 1:
The optical properties of the electrode structure are improved by changing parameters such as the thickness of the dielectric layer (optimized to be greater than one-quarter wavelength of the emitted light) and the refractive index of materials. These parameter changes enhance light reflection and extraction efficiency while maintaining compatibility with existing manufacturing processes.
3Loss of energy
If a thick dielectric layer is added to enhance light reflection, then internal absorption is reduced, but the device structure becomes more complex
Solution Approach 1:
The dielectric layer is applied selectively in specific locations where it is most needed for light reflection, rather than uniformly throughout the entire device. This localized application reduces the overall structural complexity while still achieving the goal of minimizing internal absorption in critical areas.
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 increases the brightness and efficiency of LEDs, making them more suitable for a wider range of applications, including general illumination by minimizing light absorption and maximizing light extraction.
Implementation Method 1
The electrode cooperates with the thick dielectric to enhance reflection such that light emitted in the direction of the electrode is reflected back into the semiconductor material
Implementation Method 2
A series of DBR pairs can be formed upon the thick silicon dioxide material
Data Source
AI summary
Aspects include Light Emitting Diodes that have a GaN-based light emitting region and a metallic electrode. The metallic electrode can be physically separated from the GaN-based light emitted region by a layer of porous dielectric, which provides a reflecting region between at least a portion of the metallic electrode and the GaN-based light emitting region.