Micro-LED Optics and Stepped Mesa for Lower Optical Cross-Talk
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Solution Overview
Problem
Existing micro-sized light-emitting diodes (µLEDs) face limitations in density due to optical interference and cross-talk, which constrain the number of communication channels per unit area.
Innovation Solution
The fabrication method involves epitaxial growth of semiconductor layers, selective etching to form a stepped mesa without sidewall bumps, and the application of nano-imprinted optics to focus and collimate light emission, reducing optical interference and cross-talk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If µLED density is increased to allow more communication channels per unit area, then channel capacity improves, but optical interference and cross-talk increase
Solution Approach 1:
The patent applies local quality by creating asymmetric stepped mesa structures where different regions of the µLED have different heights. The first mesa region extends beyond the second mesa region, allowing selective light emission and extraction paths. This local structural differentiation enables adjacent µLEDs to be placed closer together while maintaining optical isolation, thus increasing channel density without proportionally increasing cross-talk.
Solution Approach 2:
The patent introduces a vertical dimension through the stepped mesa structure, creating multiple height levels (first and second mesa regions at different heights). This vertical stratification allows light to be extracted at different levels and angles, separating the optical paths of adjacent µLEDs in the horizontal plane. By utilizing the vertical dimension, the patent enables higher horizontal density while maintaining optical isolation between channels.
2Ease of manufacture
If conventional LED fabrication is used, then manufacturing is simpler, but side-wall bumps form increasing device size and light emission from sides
Solution Approach 1:
The patent segments the mesa structure into distinct first and second mesa regions with different heights. This segmentation is achieved through selective epitaxial growth and etching processes that create the stepped configuration. By dividing the originally uniform mesa into segmented regions, the patent eliminates side-wall bumps while maintaining manufacturing feasibility through modified standard processes.
Solution Approach 2:
The patent changes the structural parameters of the mesa by creating a stepped height profile instead of a uniform structure. Through controlled epitaxial growth and selective removal of semiconductor layers, the patent transforms the mesa from a single-level structure to a multi-level structure, reducing the horizontal footprint and eliminating side-wall bumps while maintaining electrical functionality.
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 µLED density and efficiency by minimizing physical size and unwanted light emission, allowing closer spacing of µLEDs and reducing cross-talk, thereby enabling higher channel densities and improved light extraction.
Implementation Method 1
the nano-imprinted optic may reduce optical interference between nearby LEDs by focussing and/or collimating the emitted light
Implementation Method 2
the nano-imprinted optic may reduce optical interference between nearby LEDs by focussing and/or collimating the emitted light
Implementation Method 3
The optical relay comprises a first lens, a turning prism arranged downstream of the first lens or an optical path, and a second lens arranged downstream of the turning prism on the optical path
Implementation Method 4
The method includes epitaxially growing a layer of a first semiconductor over a substrate; and epitaxially growing a layer of a second semiconductor over the layer of the first semiconductor
Implementation Method 5
Subsequently, the method includes selectively etching the layers to form a mesa; and selectively etching the mesa to remove a portion of the second semiconductor along one edge of the mesa
Data Source
Figure 1~2
Figure 3A~3D
Figure 4~5A
AI summary
A method of manufacturing a light-emitting diode device comprises fabricating a light-emitting diode structure comprising an inorganic semiconductor; and fabricating an optic over the light-emitting diode structure using nano-imprint lithography. The method may further comprise, before fabricating the optic, forming a first lens on the light-emitting diode structure by thermal reflow lithography. The optic and first lens may improve the efficiency of the light-emitting diode device by reducing losses due to total internal reflection. Also provided are light emitting diode devices obtainable by the method.