μLED Regrowth and ELO Transfer for Surface Loss Reduction
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Solution Overview
Problem
III-nitride micro-light emitting diodes (μLEDs) face inefficiencies due to nonradiative recombination losses at exposed surfaces, especially as device dimensions shrink, leading to size-dependent efficiency issues, color gamut limitations, and challenges in mass-transfer techniques.
Innovation Solution
The method involves growing island-like III-nitride semiconductor layers using epitaxial lateral overgrowth (ELO) on a substrate with a growth restrict mask, allowing for reduced dislocation densities and stacking faults, and using epitaxial or non-epitaxial bridges to separate and transfer μLEDs with minimal damage, enabling better crystal quality and increased yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If device dimensions are reduced to achieve micro-scale μLEDs, then display resolution and integration density are improved, but nonradiative recombination losses at exposed surfaces increase leading to efficiency degradation
Solution Approach 1:
The patent applies selective area regrowth to convert the harmful effect of exposed surfaces (which cause nonradiative recombination) into a beneficial process. By performing regrowth only in specific areas where defects are present, the method transforms the surface exposure problem into an opportunity to selectively repair damaged regions while preserving the benefits of miniaturization.
Solution Approach 2:
The invention implements local quality by applying regrowth treatment only to specific regions rather than uniformly across the entire device. The selective area regrowth targets only those areas with exposed surfaces and defects, creating locally improved crystal quality without requiring uniform treatment of the whole structure, thus maintaining efficiency while preserving small device dimensions.
2Ease of manufacture
If conventional fabrication methods are used, then manufacturing process is simpler, but crystal quality contains high dislocation densities and stacking faults
Solution Approach 1:
The patent employs preliminary action by performing regrowth before final device completion and transfer. The selective area regrowth is conducted on the substrate while devices are still in place, addressing crystal quality issues proactively before the devices are separated and integrated into final applications, thereby preventing defect propagation without requiring complex post-processing.
Solution Approach 2:
The regrowth process acts as an intermediary step between conventional fabrication and final device assembly. This intermediate treatment phase allows crystal quality improvement through selective regrowth without disrupting the overall manufacturing flow, serving as a bridge that enhances precision while maintaining ease of manufacture through integration into the existing process sequence.
3Adaptability or versatility
If μLEDs are separated from substrate for transfer, then device integration is enabled, but mechanical damage and yield loss occur
Solution Approach 1:
The patent applies preliminary action by completing the selective area regrowth process before device separation and transfer. This ensures that crystal quality improvements are fully realized and stabilized prior to the mechanical stresses of separation, preventing defect generation during transfer and maintaining high yield while enabling device integration.
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 improves the crystal quality of the light-emitting aperture, reduces defects, and enhances the reliability and scalability of μLEDs, facilitating their integration into display panels with higher efficiency and reduced manufacturing costs.
Implementation Method 1
growing island-like III-nitride semiconductor layers using epitaxial lateral overgrowth (ELO) on a substrate with a growth restrict mask
Data Source
AI summary
A method for fabricating and transferring high quality and manufacturable light-emitting devices, such as small sized light-emitting diodes (mLEDs), using epitaxial lateral overgrowth (ELO) and isolation methods. III-nitride ELO layers are grown on a host substrate using a growth restrict mask, and III-nitride device layers are grown on wings of the III-nitride ELO layers. The resulting devices are isolated from the host substrate while attached by a connecting link comprising an epitaxial or non-epitaxial bridge. A regrowth is performed on selected mesas of the device layers to realize improved devices with the help of the bridge. The bridge is broken, and the devices are then plucked from the host substrate and placed on a display panel.