LED Electrode Reflectivity and Stress via Composite Metal Layers
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Solution Overview
Problem
Flip-chip LEDs with metal reflective layers have incomplete surface coverage, affecting reflectivity and brightness, and the reliability of n-type ohmic contact electrodes is a concern due to the material's reflectivity and potential for reliability issues.
Innovation Solution
A light-emitting diode design featuring a transparent conductive layer, insulating layers, and a first electrode layer with a high reflectivity metal reflective layer and stress adjustment layer, where the metal reflective layer is in direct contact with the semiconductor layer, and a metal adhesive layer is used to enhance adhesion and reduce reflectivity impact, ensuring good ohmic contact and high reflectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a metal reflective layer is used to improve light reflection, then reflectivity is improved, but the metal reflective layer does not cover the whole surface and the n-type ohmic contact electrode area is exposed, reducing overall reflectivity
Solution Approach 1:
The patent employs a composite electrode layer structure consisting of multiple metal layers with different functions. The first metal reflective layer provides high reflectivity, while the second metal layer ensures complete surface coverage. This composite approach allows the electrode layer to simultaneously achieve both high reflectivity and full surface coverage, resolving the contradiction between these two requirements.
Solution Approach 2:
The electrode layer is segmented into multiple sub-layers, each with specific thicknesses and material compositions. The first metal reflective layer has optimized thickness for maximum reflection, while the second metal layer provides coverage extension. This segmentation allows independent optimization of each layer's function to achieve overall performance improvement.
2Reliability
If the n-type ohmic contact electrode material is used, then electrical conductivity is improved, but the material's reflectivity affects LED brightness and reliability is compromised
Solution Approach 1:
The patent uses a composite electrode layer with multiple metal layers. The first metal reflective layer is specifically designed with high reflectivity to improve LED brightness, while the second metal layer ensures electrical conductivity and reliability. This composite structure allows the electrode to simultaneously achieve high brightness and reliability, resolving the contradiction between these two parameters.
3Illumination intensity
If a multi-layer electrode structure is implemented to improve reflectivity and coverage, then performance is improved, but device complexity increases
Solution Approach 1:
The patent extracts and separates the different functions (reflection and coverage) into distinct metal layers. Each layer is optimized for its specific function, allowing independent design and fabrication. This extraction approach simplifies the overall design process compared to attempting to find a single material that performs both functions simultaneously, thereby reducing fabrication complexity while achieving high performance.
4Illumination intensity
If metal reflective layers are used to achieve high reflectivity, then brightness is improved, but stress management becomes challenging
Solution Approach 1:
The patent optimizes the thickness parameters of each metal layer to control internal stress. By carefully selecting the thickness of the first metal reflective layer and the second metal layer, the overall stress in the electrode structure is managed. This parameter optimization allows high reflectivity to be achieved while maintaining stress within acceptable limits, resolving the contradiction between brightness and stress management.
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 improves the reflection efficiency and brightness of the LED by achieving high reflectivity and reliability of the electrode layer, while maintaining low stress and cost, and ensuring stability against subsequent processing effects.
Implementation Method 1
the first metal reflective layer contains a metal with a reflectivity greater than 70%
Implementation Method 2
the metal adhesive layer may include at least one metal selected from chromium, titanium, and nickel
Data Source
AI summary
A light-emitting diode includes a light-emitting structure, a first insulating layer and a first electrode layer. The first electrode layer is formed on the first insulating layer and in the first opening, and is electrically connected to the first semiconductor layer through the first opening. The first electrode layer includes a first metal reflective layer and a stress adjustment layer. The first metal reflective layer in the first opening is in contact with the first semiconductor layer, and located between the first semiconductor layer and the stress adjustment layer. The first metal reflective layer and the stress adjustment layer contain a same metal element, and a content of the same metal element in the first metal reflective layer is greater than that in the stress adjustment layer.