Semiconducting Pixel With Stacked Active Layers for Miniaturization
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Solution Overview
Problem
Existing semiconductor pixel technologies face challenges in miniaturization and high luminosity, particularly for inorganic LEDs, due to complex hybridization, high electrical resistances, and light absorption issues, which limit their application in miniaturized color screens and lighting devices.
Innovation Solution
A semiconductor pixel structure comprising three adjacent sub-pixels with at least one electrically pumped and one optically pumped active layer, using inorganic semiconductors, where each sub-pixel emits light at different wavelengths, and a monolithic structure with reduced etching depth and simplified hybridization, allowing for extensive miniaturization and high luminosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If three separate LEDs are assembled to produce different colors, then color control is improved, but device complexity and miniaturization difficulty increase
Solution Approach 1:
The patent merges three separate LED structures into a single integrated semiconductor device with three active layers stacked vertically. Each active layer emits a different wavelength (blue, green, red) and can be independently controlled through electrical or optical pumping, achieving color versatility while reducing lateral footprint to enable miniaturization.
Solution Approach 2:
The patent transitions from lateral arrangement of three separate LEDs to a vertical stacking configuration. The active layers are arranged in the vertical dimension (depth) rather than horizontal dimension, allowing multiple color-emitting elements to coexist within a single pixel footprint, thus enabling miniaturization while maintaining color control capability.
2Illumination intensity
If inorganic semiconductor layers are stacked to form a complete pixel, then luminosity is improved, but manufacturing complexity and hybridization difficulty increase
Solution Approach 1:
The patent segments the pixel into three distinct active layers, each responsible for emitting a specific wavelength. This segmentation allows independent optimization of each layer's luminescent properties while maintaining a unified monolithic structure, simplifying manufacturing compared to hybridizing multiple separate LED devices.
Solution Approach 2:
The patent creates a universal active layer design that can function both as an light-emitting element and as a wavelength converter when optically pumped. Each active layer can be independently controlled to emit its characteristic wavelength or be excited by blue light to emit at longer wavelengths, providing manufacturing flexibility and reducing the need for separate control circuits.
3Adaptability or versatility
If phosphor layers are used for wavelength conversion, then color diversity is improved, but pixel miniaturization is limited due to light absorption
Solution Approach 1:
The patent changes the material parameters by using inorganic semiconductor active layers with direct bandgap properties instead of conventional phosphor materials. These semiconductor layers achieve efficient wavelength conversion at much thinner thicknesses (micrometer scale vs. hundred micrometer scale), enabling pixel miniaturization while maintaining color diversity through independent control of each active layer's emission.
4Reliability
If etching depth is increased to access active layers, then electrical connection is improved, but miniaturization capability is reduced
Solution Approach 1:
The patent inverts the conventional approach by making the top surface (where light exits) the primary functional surface rather than the bottom surface. Electrical contacts are configured to access the active layers from the top surface through shallow etching, while light extraction occurs through the same top surface. This inversion eliminates the need for deep etching through the entire stack, preserving miniaturization capability while ensuring reliable electrical connections.
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 solution enables the production of miniaturized, high-luminosity semiconductor pixels and matrices suitable for displays and lighting, with simplified manufacturing and reduced electrical losses, overcoming the limitations of previous technologies.
Implementation Method 1
a first active layer, adapted to emit light at a first wavelength when it is traversed by an electric current
Implementation Method 2
at least one of said second and third active layer being adapted to emit said light when excited by light at the first wavelength emitted by said first active layer
Implementation Method 3
said third active layer of said third sub pixel is arranged on a second side of said first active layer, opposite to said first side, and adapted to emit said light at said third wavelength when it is excited by light at the first wavelength emitted by said first layer active of said third sub-pixel
Data Source
Figure 1A~1B
Figure 1C~1E
Figure 2A~2B
AI summary
Pixel comprising three adjacent sub-pixels (P1, P2, P3), formed by respective stacks of semiconducting layers, said pixel being characterized in that: - each said sub-pixel comprises a first active layer (32), adapted to emit a light at a first wavelength (λ1) when it is traversed by an electric current; - another sub-pixel (P2) also comprises a second active layer (52, 52'), adapted to emit a light at a second wavelength (λ2) greater than said first wavelength; - another of said sub-pixels (P3) also comprises a third active layer (22, 6), adapted to emit a light at a third wavelength (λ3) greater than said first wavelength and different from said second wavelength; at least one out of said second and third active layer being adapted to emit said light when it is excited by the light of the first wavelength emitted by said first active layer of the same sub-pixel. Semi-conducting structure and methods for the fabrication of such a pixel.