Semiconductor Light Emitting Device Electrode Structure
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Solution Overview
Problem
Semiconductor light emitting devices face challenges in achieving high bondability and efficiency due to issues with current uniformity and light absorption, particularly when using the same material for base and auxiliary electrodes, which leads to poor bondability and reduced light extraction efficiency.
Innovation Solution
The use of a semiconductor light emitting device configuration with a transparent first conductive layer, a bonding pad second conductive layer with high adhesion, and a reflective third conductive layer having an extending part that spreads current uniformly, made from materials with different properties and shapes to optimize bondability and light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the same material is used for base electrode and auxiliary electrode, then manufacturing process is simplified, but bondability deteriorates
Solution Approach 1:
The electrode structure is segmented into base electrode and auxiliary electrode as separate components. The base electrode is formed first, then the auxiliary electrode is formed separately and connected to it, allowing each to be optimized for its specific function while maintaining manufacturing efficiency
Solution Approach 2:
Different materials are used for different parts of the electrode structure. The base electrode uses a material optimized for bonding (e.g., Al or Al alloy), while the auxiliary electrode uses a material optimized for current distribution and light extraction (e.g., transparent conductive oxide or metal with different properties)
2Reliability
If auxiliary electrode extends from base electrode, then current uniformity is improved, but light absorption increases
Solution Approach 1:
The auxiliary electrode is designed with local quality optimization: it extends from the base electrode to ensure uniform current distribution, but uses materials with high transparency to the emitted light wavelength, minimizing light absorption while maintaining electrical functionality
Solution Approach 2:
The electrode structure employs composite materials where the auxiliary electrode may use transparent conductive oxides or metal combinations that provide both electrical conductivity for current uniformity and optical transparency to reduce light absorption losses
3Loss of energy
If reflective layer is added to base electrode, then light extraction efficiency is improved, but device complexity increases
Solution Approach 1:
The reflective function is merged with the base electrode structure itself. The base electrode is designed to inherently provide reflection to the emitted light, combining the electrical function (current injection) and optical function (light extraction) into a single integrated component, thereby improving light extraction without adding separate reflective layers
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
This configuration ensures high bondability and luminous efficiency by making current uniform and reducing light absorption, while allowing for high light extraction efficiency through the use of materials with appropriate reflectance and adhesion properties.
Implementation Method 1
The third conductive layer has a reflectance higher than a reflectance of the second conductive layer with respect to the luminescent light
Data Source
AI summary
According to one embodiment, a semiconductor light emitting device includes a stacked structural body, a first, a second and a third conductive layer. The stacked structural body includes first and second semiconductors and a light emitting layer provided therebetween. The second semiconductor layer is disposed between the first conductive layer and the light emitting layer. The first conductive layer is transparent. The first conductive layer has a first major surface on a side opposite to the second semiconductor layer. The second conductive layer is in contact with the first major surface. The third conductive layer is in contact with the first major surface and has a reflectance higher than a reflectance of the second conductive layer. The third conductive layer includes an extending part extending in parallel to the first major surface. At least a portion of the extending part is not covered by the second conductive layer.