LED Trench Electrode Cavity Structure for Light Extraction
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Solution Overview
Problem
Current light-emitting diodes (LEDs) face challenges in achieving optimal light extraction efficiency and reliability due to issues with current spreading and moisture protection, particularly in high-voltage chip configurations where the trench structure and electrode pads can lead to stress and moisture infiltration.
Innovation Solution
The design incorporates a light-emitting device with a trench separating light-emitting elements, a protective layer, and electrode pads with a cavity or patterned sacrificial layer to improve light extraction efficiency and reliability, featuring a Distributed Bragg Reflector structure and a reflective layer to enhance light reflection and moisture protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a large-area LED structure is used to increase light output, then light emission area is improved, but light extraction efficiency deteriorates due to increased internal reflection and reduced current spreading
Solution Approach 1:
The patent divides the large-area LED into multiple light-emitting elements arranged in series, separated by trenches. This segmentation allows each element to maintain efficient light extraction while collectively providing large total emission area. The trenches act as isolation structures that prevent current leakage and improve current spreading to each individual element.
Solution Approach 2:
The patent introduces a cavity dimension beneath the electrode pads, creating a three-dimensional structure. This cavity serves as a light reflection chamber that redirects internally reflected light back toward the emission area, effectively increasing light extraction efficiency without reducing the planar emission area.
2Device complexity
If electrode pads are placed directly on light-emitting elements to simplify structure, then device complexity is reduced, but current spreading deteriorates leading to increased forward voltage
Solution Approach 1:
The patent introduces trenches as intermediary structures between the electrode pads and light-emitting elements. These trenches filled with reflective material act as mediators that improve current spreading to the light-emitting elements while maintaining structural organization. The trenches prevent direct contact between pads and elements, allowing for better current distribution without excessive structural complexity.
3Reliability
If trenches are added to separate light-emitting elements to improve current spreading, then current distribution is improved, but device complexity increases
Solution Approach 1:
The trenches in the patent serve multiple functions simultaneously: they separate light-emitting elements to improve current spreading, act as reflective chambers to enhance light extraction, and provide structural support for the electrode pads. This multi-functionality reduces the need for additional separate structures, thereby limiting the increase in device complexity while achieving multiple performance improvements.
4Loss of energy
If cavity depth is increased to improve light reflection, then light extraction efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the cavity depth to a specific range (1-5 μm) that balances light reflection efficiency with manufacturing feasibility. Within this parameter range, the cavity provides sufficient light reflection while remaining compatible with standard semiconductor fabrication processes. The patent also specifies that the cavity depth should be 0.1-10 times the thickness of the light-emitting elements, providing a scalable parameter relationship that simplifies manufacturing 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 configuration enhances light extraction efficiency and improves the reliability of the light-emitting device by reducing current blocking effects and protecting the internal structures from moisture, while facilitating heat dissipation and packaging.
Implementation Method 1
a reflective structure to enhance light extraction
Data Source
AI summary
A light-emitting device comprises a plurality of light-emitting elements, comprising a first group light-emitting elements and a second group light-emitting elements; a trench separating the plurality of light-emitting units; a first electrode pad covering the first group light-emitting elements and located on the trench; a second electrode pad covering the second group light-emitting elements and located on the trench; and a cavity located on the trench, formed between the first electrode pad and the protective layer or formed between the second electrode pad and the protective layer.