Epitaxial LED Light Control Features Without Quantum Well Etching
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Solution Overview
Problem
Conventional light emitting diodes (LEDs) face challenges in achieving high light extraction efficiency and directionality, particularly due to the limitations of photonic crystal (PhC) fabrication techniques which require delicate fabrication and are not suitable for mass production, and existing methods can damage quantum wells during etching processes.
Innovation Solution
The method involves epitaxially integrating light control features directly onto the epitaxial layer of LEDs using selective area growth (SAG) or epitaxial lateral overgrowth (ELO) techniques, allowing for the formation of defect-filtered crystalline structures without physical etching, enabling the creation of macro-sized to micro-sized LEDs with improved crystal quality and light control features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If photonic crystal (PhC) fabrication techniques are used to enhance light extraction efficiency and directionality, then light extraction efficiency is improved, but fabrication complexity increases and quantum wells may be damaged during etching processes
Solution Approach 1:
The patent applies preliminary action by forming photonic crystal patterns on the substrate before epitaxial growth of the LED layers. This allows the PhC structures to be created in advance using lithography and etching on the substrate, which then serve as templates during subsequent epitaxial growth. The patterns are transferred to the LED structure without requiring post-growth etching, thus preventing quantum well damage while achieving the desired light extraction enhancement.
Solution Approach 2:
The patent uses the substrate as an intermediary carrier for the photonic crystal patterns. The PhC structures are first fabricated on the substrate, which acts as a temporary holder and transfer medium. During epitaxial growth, the patterns are replicated onto the LED layers through the substrate, allowing the complex PhC structures to be transferred without direct manipulation of the fragile quantum wells.
2Illumination intensity
If photonic crystal (PhC) fabrication techniques are used to enhance light extraction efficiency and directionality, then light extraction efficiency is improved, but manufacturing difficulty increases due to delicate fabrication requirements
Solution Approach 1:
The patent performs preliminary fabrication of photonic crystal patterns on the substrate before LED epitaxial growth. This approach allows standard lithography and etching processes to be used on the robust substrate, avoiding the need for delicate post-growth processing. The pre-formed patterns are then transferred to the LED structure during growth, simplifying manufacturing by performing complex steps when the substrate is most robust.
Solution Approach 2:
The patent replaces mechanical post-growth etching processes with an epitaxial growth-based pattern transfer method. Instead of using mechanical or chemical etching to create PhC structures after the LED is grown (which would damage quantum wells), the method uses controlled epitaxial growth to replicate the substrate patterns directly onto the LED layers, substituting a gentler, more manufacturing-friendly process.
3Illumination intensity
If conventional etching processes are used to create light control features, then light extraction is enhanced, but quantum wells are damaged during the etching process
Solution Approach 1:
The patent creates light control features through preliminary patterning on the substrate before epitaxial growth, rather than etching after growth. The PhC patterns are formed on the substrate first, then the LED layers are grown conformally over these patterns. This eliminates the need for post-growth etching that would expose and damage the quantum wells, while still achieving the desired light extraction enhancement.
Solution Approach 2:
The patent uses the epitaxial growth process as an intermediary mechanism to transfer patterns without direct contact with quantum wells. The substrate patterns serve as a template, and the epitaxial growth process replicates these patterns onto the LED structure through vapor-phase deposition. This intermediary approach avoids direct etching of the quantum wells, preserving their integrity while creating the necessary light control features.
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 enhances light extraction and directionality while reducing defect density, improving the electrical conductivity and crystal quality of LEDs, making them suitable for next-generation display applications with increased efficiency and thermal stability.
Implementation Method 1
epitaxially integrated light control features to extract, guide, reflect, refract, focus or defocus light emitted from the device layers
Data Source
AI summary
A method for fabricating epitaxial light control features, without reactive ion etching or wet etching, when active layers are included. The epitaxial light control features comprise light extraction or guiding structures integrated on an epitaxial layer of a light emitting device such as a light emitting diode. The light extraction or guiding structures are fabricated on the epitaxial layer using an epitaxial lateral overgrowth (ELO) technique. The epitaxial light control features can have many different shapes and can be fabricated with standard processing techniques, making them highly manufacturable at costs similar to standard processing techniques.