Monolithic RGB InGaN MicroLED Structure for Sub-10 µm Pixels
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Solution Overview
Problem
The development of efficient microLEDs with sub-10 µm pixel sizes is challenging due to efficiency losses from side-wall damages during dry etching and the inefficiency of red light emission. Additionally, current methods for assembling RGB pixels are not technologically mature, especially for pixel sizes below 10 µm.
Innovation Solution
The proposed solution involves the monolithic growth of RGB microLEDs from a common epiwafer using InGaN platelets with quantum well layers grown at specific heights to control emission wavelengths. This approach eliminates the need for mass transfer and allows for direct bonding of RGB sub-pixels to driving circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixel size is reduced to achieve high resolution displays, then display resolution is improved, but external quantum efficiency deteriorates due to increased side-wall damages from dry etching
Solution Approach 1:
The patent divides the pixel structure into multiple segments: a top c-plane surface for light emission and side walls for structural support. By segmenting the pixel into these functional zones, the invention allows the top surface to maintain high efficiency while the side walls provide mechanical stability, thus resolving the contradiction between small pixel size and efficiency loss from etching damages.
Solution Approach 2:
The invention applies local quality by creating a truncated pyramid structure where the top c-plane surface has different properties (flat, emission-oriented) compared to the side walls (structural support). This localized differentiation allows the emission surface to optimize for efficiency while the side walls handle structural requirements, mitigating the efficiency loss from dry etching at small pixel sizes.
2Manufacturing precision
If conventional dry etching is used for pixel fabrication, then pixel structure is formed, but side-wall damages increase causing efficiency loss
Solution Approach 1:
The patent performs preliminary action by forming the complete pixel structure including the truncated pyramid shape before the dry etching process. By pre-forming the structure with desired geometry, the subsequent etching process causes minimal damage to the critical emission surfaces, thus maintaining high external quantum efficiency while achieving precise pixel structure formation.
Solution Approach 2:
The invention inverts the conventional approach by growing the pixel structure from the substrate upward to form truncated pyramids with flat top surfaces, rather than etching away material to create pixels. This growth-based formation method minimizes side-wall damages compared to etching-based methods, preserving efficiency while achieving precise structural formation.
3Productivity
If red light emitting microLEDs are fabricated using conventional methods, then red pixels are produced, but efficiency and brightness are insufficient
Solution Approach 1:
The patent applies parameter changes by optimizing the composition and structure of the active region in red light emitting microLEDs. By adjusting material parameters such as indium content in InGaAsP quantum wells and optimizing layer thicknesses, the invention simultaneously improves both emission efficiency and brightness, overcoming the limitations of conventional red microLED fabrication methods.
4Adaptability or versatility
If RGB pixels are assembled using pick and place methods, then color display is achieved, but the process is not mature for sub-10 µm pixel sizes
Solution Approach 1:
The patent merges all three color pixels (RGB) into a single integrated structure grown from one substrate. By combining the fabrication of red, green, and blue pixels into a unified growth process rather than separate assembly steps, the invention achieves color display capability while eliminating the need for immature pick and place assembly methods for sub-10 µm pixels.
Solution Approach 2:
The invention creates a universal substrate that can produce all three color pixels simultaneously through a single epitaxial growth process. This multi-functional approach allows the same substrate and growth conditions to generate RGB pixels, eliminating the need for separate assembly processes and achieving maturity for sub-10 µm pixel fabrication.
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 solution achieves high external quantum efficiencies for all three colors, enabling the production of microLEDs with sub-10 µm pixel sizes and improved red light emission, while also simplifying the assembly process by integrating RGB pixels on a single wafer.
Implementation Method 1
a plurality of InGaN platelets monolithically grown on the epiwafer, each comprising a quantum well layer... each InGaN platelet configured for emission of one colour of RGB
Implementation Method 2
each comprising a quantum well layer... The QW layer is configured at different height over a surface of the epiwafer in the respective InGaN platelets, wherein said height correlates with emission wavelength
Data Source
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AI summary
The proposed solution relates to a semiconductor structure (80) for micro light-emitting diodes, microLEDs, comprising an epiwafer (10) and a plurality of InGaN platelets (100) monolithically grown on the epiwafer. Each InGaN platelet comprises a QW layer. The plurality of InGaN platelets comprises individual InGaN platelets configured for red, green, and blue light emission, respectively. The solution further relates to a microLED device (800) comprising the semiconductor structure, and a method for fabricating the semiconductor structure.