LED Contact Layer Morphology for Light Extraction
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Solution Overview
Problem
Conventional light-emitting diode structures face challenges in achieving balanced current spreading and high light extraction efficiency due to surface irregularities in current spreading layers, which can decrease their effectiveness.
Innovation Solution
The proposed solution involves forming a light-emitting device with a contact layer having both rough and flat structures, where the current spreading layer is also designed with matching surface morphologies, ensuring that the rough regions for high light extraction efficiency overlap with the rough contact layer regions, while flat regions provide effective current spreading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a rough contact layer is formed to increase light extraction efficiency, then light extraction efficiency is improved, but current spreading effect is degraded
Solution Approach 1:
The contact layer is divided into different regions with different surface morphologies: a first region with a first surface morphology and a second region with a second surface morphology. This local differentiation allows the first region to optimize for light extraction while the second region optimizes for current spreading, resolving the contradiction between these two functions.
2Reliability
If a flat current spreading layer is formed to maintain good current spreading, then current spreading effect is improved, but light extraction efficiency is reduced
Solution Approach 1:
The current spreading layer is divided into different regions with different surface morphologies: a first region with a first surface morphology and a second region with a second surface morphology. This local differentiation allows the first region to optimize for light extraction while the second region optimizes for current spreading, resolving the contradiction between these two functions.
3Ease of manufacture
If the surface morphology of contact layer and current spreading layer are made substantially the same, then manufacturing complexity is reduced, but the ability to simultaneously optimize both light extraction and current spreading is compromised
Solution Approach 1:
The contact layer and current spreading layer are both divided into regions with different surface morphologies. The first region of the contact layer and the first region of the current spreading layer have matching morphologies optimized for light extraction, while the second regions have matching morphologies optimized for current spreading. This approach maintains manufacturing simplicity while enabling simultaneous optimization of both functions through localized morphology control.
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 approach enhances light extraction efficiency by over 30% and maintains good current spreading effects, improving overall light-emitting performance by aligning the surface morphologies of the contact and current spreading layers.
Implementation Method 1
a contact layer having roughing surface can be formed directly by the epitaxy technology. It can reduce the probability of the total reflection of the light emitted from the active layer and increase more than 30% of the light extraction efficiency.
Implementation Method 2
When an electrode is formed on the contact layer, the ohmic contact is formed as a result of a lower contact resistance of the junction between the electrode and the contact layer.
Data Source
AI summary
The application illustrates a light-emitting device including a contact layer and a current spreading layer on the contact layer. A part of the contact layer is a rough structure and a part of the contact layer is a flat structure. A part of the current spreading layer is a rough structure and a part of the current spreading layer is a flat structure. The rough region of the contact layer and the rough region of the current spreading layer are substantially overlapped.