Micro-LED Microlens Layout for Narrow Radiation Distribution
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Solution Overview
Problem
Micro-LEDs with indium-doped GaN active regions suffer from efficiency and uniformity issues due to indium doping challenges, especially at small sizes, and photon extraction becomes increasingly difficult with decreasing pixel pitch, leading to inefficiencies and potential color purity loss.
Innovation Solution
Employing undoped GaN or low indium doped GaN LEDs coupled with photonically pumped quantum dots and optical cavities, including reflective cavity walls, light extracting materials, and micro-lenses to enhance photon extraction and maintain color purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If high indium content is used in micro-LEDs to achieve longer wavelength emission, then the emission wavelength is extended, but efficiency and uniformity deteriorate due to indium doping challenges
Solution Approach 1:
The patent introduces an intermediary quantum dot layer that absorbs blue light from undoped GaN micro-LEDs and converts it to red light. This mediator approach avoids the indium doping problems while achieving long wavelength emission, as the quantum dots handle the wavelength conversion rather than relying on high-indium GaN layers
Solution Approach 2:
The patent changes the fundamental parameter approach by using undoped or low-indium GaN micro-LEDs combined with quantum dot wavelength conversion, rather than attempting to achieve red emission directly through high-indium GaN. This parameter change from direct emission to wavelength conversion resolves the doping uniformity issues
2Length of moving object
If micro-LED size is reduced for display applications, then device integration is improved, but indium doping uniformity worsens making efficient photon extraction difficult
Solution Approach 1:
The quantum dot layer serves as an intermediary that converts wavelength rather than relying on precise indium doping in small micro-LEDs. This allows miniaturization while avoiding the doping uniformity problems that plague small high-indium GaN structures
Solution Approach 2:
The patent substitutes the mechanical/diffusion-based indium doping process with a photonic approach using quantum dots. Instead of relying on precise material deposition and thermal diffusion to achieve uniform indium distribution, the system uses optical absorption and photoluminescence conversion which are more readily controllable at small scales
3Illumination intensity
If conventional LEDs with wide radiation patterns are used, then light output is distributed broadly, but optical coupling efficiency with display devices deteriorates
Solution Approach 1:
The patent applies local quality by placing individual micro-lenses over each micro-LED to locally control and direct the radiation pattern. This localized optical element modifies the emission characteristics of each LED individually, concentrating light in the desired direction to improve coupling efficiency with the display device
Solution Approach 2:
The micro-lenses utilize curved spherical surfaces to refract and direct the light from each micro-LED. The spherical geometry of the lenses focuses and collimates the emitted light, transforming the wide Lambertian radiation pattern into a more directional beam that couples efficiently with the display device
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
Improves efficiency and uniformity across micro-LED arrays by effectively extracting photons and preventing loss, ensuring high quantum efficiency and color purity, particularly in augmented reality displays.
Implementation Method 1
a plurality of quantum dots in a matrix material, each quantum dot configured to absorb a photon from a respective one of the plurality of light emitting diodes and emit a converted photon
Implementation Method 2
Each of the plurality of micro-lenses is located over a respective one of the plurality of light emitting diodes... generating narrow angular radiation distributions
Implementation Method 3
a plurality of light emitting diodes located over the substrate... configured to emit light of a first wavelength
Data Source
AI summary
A light emitting device includes a substrate, a plurality of light emitting diodes located over the substrate, and a plurality of micro-lenses. Each of the plurality of micro-lenses is located over a respective one of the plurality of light emitting diodes. Each of the plurality of micro-lenses has a first symmetry axis, each of the plurality of light emitting diodes has a second symmetry axis, and at least some of the plurality of micro-lenses have the first symmetry axis which is laterally displaced relative to the second symmetry axis of the respective one of the plurality of light emitting diodes.