μ-LED Array Structures for Directional Emission and Uniform Brightness
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Solution Overview
Problem
The challenges posed by the small size of light-generating components in μ-LEDs, such as μ-displays, result in difficulties in production and processing, leading to issues like the fly screen effect and limitations in achieving high directional radiation and uniform brightness, especially in augmented reality and automotive applications.
Innovation Solution
The use of monolithic and non-monolithic μ-LED arrays, combined with slotted antenna structures and photonic crystals, to enhance directional light emission and reduce non-radiative recombination, along with the integration of converter materials to generate desired colors and improve brightness uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the size of light-generating components is reduced to achieve high resolution, then resolution is improved, but manufacturing difficulty increases and non-radiative recombination increases
Solution Approach 1:
The patent divides the light-generating component into separate functional segments: a μ-LED core structure for light generation and a photonic crystal structure for light extraction enhancement. This segmentation allows each part to be optimized independently, enabling high resolution while managing manufacturing complexity through modular fabrication processes.
Solution Approach 2:
The patent implements a nested structure where the photonic crystal lattice is integrated around and with the μ-LED core. The photonic crystal cavities and waveguides are positioned in close proximity to the active region, creating a hierarchical structure that enhances light extraction efficiency without increasing overall device footprint, thus maintaining high resolution while improving manufacturability.
2Measurement precision
If the size of light-generating components is reduced to achieve high resolution, then resolution is improved, but non-radiative recombination increases
Solution Approach 1:
The patent applies local quality enhancement by positioning photonic crystal structures with specific refractive index properties directly around the active region of the μ-LED. The photonic crystal cavities are strategically located to create localized optical fields that enhance radiative recombination rates specifically at the quantum well regions, counteracting the increased non-radiative recombination that occurs in smaller devices.
Solution Approach 2:
The patent converts the harmful effect of increased non-radiative recombination in miniaturized devices into a benefit by using photonic crystal structures to create optical cavities that trap and enhance radiative emission. The photonic bandgap structure prevents non-radiative pathways while enhancing radiative channels, effectively transforming the limitation of small size into an opportunity for enhanced light extraction efficiency.
3Ease of manufacture
If conventional LED structures are used, then manufacturing is simpler, but directional radiation and brightness uniformity are insufficient
Solution Approach 1:
The patent employs composite material structures combining conventional LED materials (GaN-based semiconductors) with photonic crystal materials (dielectric layers with alternating refractive indices). This composite approach allows the device to maintain the manufacturing advantages of conventional LED processes while incorporating photonic crystal structures that provide enhanced directional radiation control and improved brightness uniformity through constructive and destructive interference effects.
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 high-resolution, low-energy μ-LED displays with improved directional radiation, reduced crosstalk, and enhanced brightness uniformity, suitable for augmented reality and automotive applications, including curved surfaces and integrated sensors.
Implementation Method 1
The length of the cavity is based essentially on n/2 of a wavelength of light to be emitted during operation... the electrically conductive structure forms a slotted antenna structure and has an upper main surface and a lower main surface opposite the upper main surface
Implementation Method 2
The semiconductor layer stack... extends at least over the upper main surface... with a first electrical contact, a second electrical contact and an active area
Implementation Method 3
combined with slotted antenna structures and photonic crystals, to enhance directional light emission and reduce non-radiative recombination
Implementation Method 4
the integration of converter materials to generate desired colors and improve brightness uniformity
Data Source
AI summary
The invention relates to various aspects of a μ-LED or a μ-LED array for augmented reality or lighting applications, in particular in the automotive field. The μ-LED is characterized by particularly small dimensions in the range of a few μm.