Micro-LED Fabrication With Bottom Emission and Color Conversion
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Solution Overview
Problem
Current micro-LED technologies face challenges in improving light extraction efficiency, modifying light color, and controlling angular output, which limits their practical application in commercial displays.
Innovation Solution
A method involving the fabrication of micro-light emitting diodes (micro-LEDs) by patterning an epitaxial semiconductor layer, bonding it to a carrier substrate, and electrically coupling drive circuitry for individual addressability, while incorporating optical features and color conversion layers to enhance light management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional LED packaging techniques are used for micro-LEDs, then manufacturing simplicity is maintained, but light extraction efficiency deteriorates and source position is scrambled
Solution Approach 1:
The patent inverts the conventional LED packaging approach by extracting light from the semiconductor side rather than through the sapphire substrate. This inversion allows the micro-LED structure to maintain manufacturing simplicity while dramatically improving light extraction efficiency and preserving source position information, as the light exits directly from the active region without traversing the substrate.
Solution Approach 2:
The patent introduces a vertical dimension to light extraction by creating a reflective structure at the bottom of the semiconductor layer. This allows light to be extracted upward through the semiconductor side, adding a new extraction pathway that complements traditional side-emission approaches and improves overall extraction efficiency without complicating the packaging process.
2Ease of manufacture
If light is extracted through the sapphire layer, then manufacturing process is simplified, but source position information is lost due to waveguiding
Solution Approach 1:
Instead of extracting light through the sapphire substrate as in conventional designs, the patent inverts the extraction direction to pull light out from the semiconductor side. This preserves the spatial mapping of light sources to pixel positions while maintaining a relatively simple manufacturing process, as it leverages the existing micro-LED array structure without requiring complex substrate removal or reconfiguration.
3Ease of operation
If both n- and p- sides are contacted from the top side, then connection simplicity is achieved, but fill factor deteriorates due to interconnect area sharing
Solution Approach 1:
The patent moves the contact points to the bottom side of the micro-LED structure, utilizing the vertical dimension to separate interconnect locations from the light-emitting area. This allows the top surface to be fully dedicated to light emission, maximizing fill factor, while the bottom contacts provide simple electrical access without interfering with the optical active area.
4Illumination intensity
If micro-LED structures are used, then high luminance pixelated structures are achieved, but light extraction efficiency and color control deteriorate
Solution Approach 1:
The patent inverts the light extraction direction to pull light out from the semiconductor side rather than through the substrate. This inversion significantly improves light extraction efficiency by eliminating waveguiding losses in the substrate, while preserving the high luminance characteristics of micro-LEDs. The approach maintains the compact pixelated structure needed for displays while extracting more light from each micro-LED element.
Solution Approach 2:
The patent modifies the optical parameters of the micro-LED structure by introducing a reflective layer at the bottom of the semiconductor and adjusting the refractive index profile. These parameter changes enhance light extraction efficiency and enable better color control by managing the optical modes within the micro-LED cavity, while maintaining the high luminance output required for display applications.
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 enables improved light extraction efficiency, color modification, and angular control, leading to higher performance and cost-effectiveness in micro-LED displays with increased active area utilization and flexibility in light extraction.
Implementation Method 1
an epitaxial semiconductor layer grown on a first face of the growth substrate
Implementation Method 2
bonding the common contact to a carrier substrate
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A system and method of are described related to structures that enable or facilitate improvement of micro-LED elements including contact, attachment, and integration of optical components. Implementations may benefit color conversion and optimization, light extraction angle, extraction efficiency, and contact reliability.