Monolithic RGB LED Matrix Growth for Microscopic Pixel Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for manufacturing GaN-based LEDs face challenges such as complex and expensive processing steps, reduced external quantum efficiency, and issues with miniaturization, particularly in forming full-color RGB pixels with microscopic LEDs, where uniformity of wavelength and thickness are difficult to achieve, leading to power leakage and low luminance yield.
Innovation Solution
A method involving epitaxial growth on a sacrificial GaN layer to form arrays of LED elements of different colors, with sequential processing and masking techniques, allowing for the variation of InGaN layer composition and thickness to control light wavelength and luminance, and the use of trench formation and nanoimprint lithography to define lateral dimensions, enabling the production of monolithic RGB pixels on a single substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional back-end processing with chip fabrication and pick-and-place is used, then LED components can be individually packaged and interconnected, but the processing becomes more difficult with miniaturisation and scaling
Solution Approach 1:
The patent merges multiple LED color elements (red, green, blue) onto a single substrate using epitaxial growth, eliminating the need for separate chip fabrication, dicing, and pick-and-place assembly. This integration directly resolves the contradiction by simplifying manufacturing processes while enabling miniaturization of display devices.
Solution Approach 2:
The patent segments the substrate into distinct regions for different LED colors during epitaxial growth, with each color element formed in a specific patterned area. This allows independent control and optimization of each color region while maintaining overall manufacturing simplicity.
2Length of moving object
If LED size is reduced to microscopic dimensions, then miniaturisation is achieved, but full-colour operation and external quantum efficiency are compromised
Solution Approach 1:
The patent applies local quality by optimizing the epitaxial growth conditions and layer structures specifically for microscopic LED dimensions. Each color element's active layer thickness and composition are locally tuned to maintain high external quantum efficiency despite the reduced overall size, ensuring reliable full-color operation at microscopic scales.
3Adaptability or versatility
If InGaN layer composition is varied to tune wavelength, then light color control is improved, but wavelength and thickness uniformity becomes difficult to achieve
Solution Approach 1:
The patent employs preliminary action by pre-planning and pre-configuring the epitaxial growth process with precisely controlled indium composition gradients and layer thickness sequences. This preliminary structuring of the growth parameters ensures that wavelength uniformity is maintained across different color elements while still allowing the necessary composition variation for color tuning.
4Ease of manufacture
If sequential epitaxial growth with masking is used, then integrated processing of different colors is achieved, but processing steps increase
Solution Approach 1:
The patent applies universality by using a single epitaxial growth process to simultaneously form multiple LED color elements with different compositions and structures. The masking and patterning steps serve multiple functions: defining color regions, controlling layer thickness, and guiding subsequent processing, thereby reducing the need for separate fabrication sequences for each color.
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 efficient and integrated processing of LEDs of different colors on a single substrate, improving luminance uniformity and external quantum efficiency, reducing processing complexity, and enhancing the yield of microscopic LEDs, while allowing for precise control of light emission characteristics.
Implementation Method 1
The InGaN layer may be formed of a mixture of GaN and indium nitride (InN), and the wavelength of the light emitted by the InGaN layer can be tuned by varying the GaN/InN ratio and also by controlling the thickness of the InGaN layer
Implementation Method 2
The first, second and third arrays of LED elements are formed by means of epitaxial growth on a sacrificial layer comprising GaN
Data Source
AI summary
A method for forming a matrix of light-emitting diode (LED) elements (11, 21, 31) of different colours is provided. The method comprises epitaxially growing, on a GaN sacrificial layer (140), a first n-doped GaN layer (111), a first InxGa(1-X)N layer (112) and a first p-doped GaN layer (113) to form a first array of first LED elements (11) for emitting light of a first colour, and forming a first etch mask (151) comprising a plurality of first trenches (161). The method further comprises: epitaxially growing a second array of second LED elements (21), for emitting light of a second colour, in the plurality of first trenches; forming a second etch mask (152) protecting the second array and comprising a plurality of second trenches (162); and epitaxially growing a third array of third LED elements (31), for emitting light of a third colour, in the plurality of second trenches.