Multi-Color Micro-LED Structure Without Etched Mesa Sidewalls
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Solution Overview
Problem
Micro-LEDs for displays face efficiency issues due to high defect densities at mesa sidewalls caused by etching, leading to non-radiative recombination and reduced light emission efficiency, especially in small-sized micro-LEDs used in augmented and virtual reality applications.
Innovation Solution
A monolithic micro-LED device is fabricated using multiple epitaxial overgrowth processes without etching, where active regions for different colors are grown on adjacent semiconductor structures or different facets of the same structure, reducing defect densities and improving light emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If micro-LEDs are fabricated using conventional etching processes to create mesa structures, then the devices can be formed with defined geometries, but high defect densities are introduced at sidewalls causing non-radiative recombination and reduced light emission efficiency
Solution Approach 1:
Instead of etching away material to create mesa structures, the patent inverts the approach by epitaxially growing semiconductor structures directly on the substrate in desired patterns. This growth-based approach creates defined geometries without the harmful sidewall defects introduced by etching, thereby maintaining manufacturing precision while eliminating the reliability issue of reduced light emission efficiency
Solution Approach 2:
The patent extracts and eliminates the etching step from the fabrication process entirely. By removing the etching operation that creates mesa structures, the harmful sidewall defects are avoided, allowing micro-LEDs to maintain high light emission efficiency while still achieving the necessary geometric definition through selective epitaxial growth
2Adaptability or versatility
If multiple etching and growth steps are used to create multi-color micro-LEDs on the same die, then color diversity is achieved, but device complexity and fabrication difficulty increase
Solution Approach 1:
The patent segments the fabrication process into distinct epitaxial growth stages, where each stage grows semiconductor structures with specific compositional characteristics for different colors. By segmenting the growth process and controlling composition at each stage, multi-color micro-LEDs are achieved on the same die without requiring complex etching and regrowth cycles, thereby reducing overall fabrication complexity
Solution Approach 2:
The patent utilizes parameter changes in the epitaxial growth process, specifically varying the compositional parameters during different growth stages to produce semiconductor structures with different optical properties. By changing composition parameters rather than relying on multiple etching and growth cycles, the patent achieves multi-color emission capability while simplifying the fabrication process
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 approach enhances the efficiency of micro-LEDs by reducing non-radiative recombination at sidewalls, allowing for the creation of multi-color micro-LEDs on a single die with improved light emission characteristics suitable for high-resolution displays in augmented and virtual reality systems.
Implementation Method 1
Light emitting diodes (LEDs) convert electrical energy into optical energy
Implementation Method 2
multiple epitaxial overgrowth processes without etching, where active regions for different colors are grown on adjacent semiconductor structures
Data Source
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AI summary
A light source includes a substrate, an array of semiconductor structures grown on the substrate, and multi-color micro-LEDs grown on surfaces of the array of semiconductor structures. Each semiconductor structure of the array of semiconductor structures has a shape of a truncated pyramid. The light source includes multiple sets of micro-LEDs formed on top surfaces of multiple sets of semiconductor structures of the array of semiconductor structures, or formed on the top surfaces and/or multiple sidewall surfaces of the array of semiconductor structures. The multiple sets of micro-LEDs are configured to emit light of multiple colors.