3D LED Contact Structure for Low Resistance and Light Extraction
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Solution Overview
Problem
Existing electroluminescent diodes (LEDs) with micronic dimensions face challenges such as high contact resistance due to small contact areas, leading to performance degradation and reduced light extraction efficiency.
Innovation Solution
A three-dimensional, non-flat contact structure is introduced, featuring a lower and upper surface with hollow or protruding patterns, covered by an electrically conductive material. This structure increases the contact area without expanding the LED's lateral dimensions, reducing contact resistance and enhancing light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the lateral dimensions of the LED are reduced to increase display resolution, then the display resolution is improved, but the contact area is reduced leading to high contact resistance
Solution Approach 1:
The contact structure transitions from a planar two-dimensional configuration to a three-dimensional vertical structure by creating hollow patterns with depth. This dimensional change allows the contact area to extend in the vertical dimension while maintaining a small lateral footprint, thereby increasing the effective contact area without compromising display resolution.
Solution Approach 2:
The contact structure embeds hollow patterns within the semiconductor layer, creating a nested configuration where the conductive material fills the hollow regions. This nesting approach maximizes the contact interface area within the constrained lateral dimensions of the micron-sized LED.
2Reliability
If the contact area is increased to reduce contact resistance, then the contact resistance is reduced, but the lateral dimensions of the LED must be increased
Solution Approach 1:
Instead of expanding the contact area laterally, the invention exploits the vertical dimension by creating hollow patterns with controlled depth. This allows the contact structure to achieve a large effective area through vertical extension rather than lateral expansion, maintaining compact LED dimensions.
Solution Approach 2:
The aspect ratio of the hollow patterns (depth to width ratio) is optimized to maximize contact area within the available vertical space. By controlling the depth and width parameters of the hollow structures, the contact resistance is reduced without requiring increased lateral dimensions.
3Ease of manufacture
If a flat contact structure is used to simplify manufacturing, then the manufacturing process is simplified, but the light extraction efficiency is low
Solution Approach 1:
The contact structure incorporates vertical hollow patterns that extend into the semiconductor layer, creating a three-dimensional configuration. This vertical structuring serves dual purposes: maintaining electrical contact functionality while simultaneously acting as an optical extraction enhancement structure that reduces total internal reflection.
Solution Approach 2:
The hollow contact structure performs multiple functions simultaneously: it provides electrical contact pathways, increases contact area for reduced resistance, and acts as an optical extraction enhancement structure. This multi-functionality eliminates the need for separate flat contact and photonic crystal structures.
4Loss of energy
If a photonic crystal structure is added to improve light extraction, then the light extraction efficiency is improved, but the device complexity increases
Solution Approach 1:
The electrical contact structure and the optical extraction enhancement structure are merged into a single integrated hollow pattern configuration. The same vertical hollow structures that provide electrical contact also serve as the extraction enhancement features, eliminating the need for separate photonic crystal layers or additional structural components.
Solution Approach 2:
The hollow contact structure is designed to simultaneously fulfill electrical and optical functions. The vertical patterns provide both conductive pathways for current and structural features for light extraction enhancement, reducing the overall device complexity compared to having separate dedicated structures for each function.
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 three-dimensional contact structure significantly reduces contact resistance, improves electrical contact quality, and achieves high light extraction efficiency, with simulations indicating an efficiency of up to 50% compared to 20-25% with traditional photonic crystals.
Implementation Method 1
The contact structure extending against the upper surface, by matching this non-planar surface... This three-dimensional structure makes it possible to increase the area of the contact surface without increasing the lateral dimensions of the LED
Implementation Method 2
Light extraction can be improved by etching the upper 30" face to produce a photonic crystal made of dielectric material... the upper surface of the upper layer forming a non-planar three-dimensional structure having hollow patterns
Data Source
Figure 1~2
Figure 3~6
Figure 7~8A
AI summary
A light-emitting diode (1) comprising a lower layer (2), an upper layer (3), and, between the two, an emitting structure (4) capable of emitting light when an electric current passes through it. The upper layer (3) is delimited by an upper surface (30), through which at least a portion of said light radiation emerges. The lower layer (2) is delimited by a lower surface (20) for injecting electrical charges. The upper surface (30) of the upper layer forms a three-dimensional non-planar structure having recessed patterns (13) and is covered by a contact structure (10) formed of one or more electrically conductive materials, which extends against said surface (30), conforming to this non-planar surface.