Integrated LED Quantum Wells for Single-Wafer Color Fabrication
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Solution Overview
Problem
Current LED manufacturing methods require separate wafers for blue, green, and red LEDs, making it difficult to achieve high resolution displays as the die size decreases, and involve complex processes for color conversion and pick-and-place operations.
Innovation Solution
The development of LED devices with photoluminescent and electroluminescent quantum wells integrated in the same semiconductor wafer, allowing for the fabrication of LEDs of different colors within the same wafer, using a bilayer contact structure and tunnel junctions to enable efficient color conversion and reduce the number of epitaxy recipes and pick-and-place operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate wafers are used for blue, green, and red LEDs, then each color can be optimized independently, but the manufacturing complexity and number of pick-and-place operations increase
Solution Approach 1:
The patent combines multiple color LEDs (blue, green, red) into a single integrated device structure where different quantum well layers are grown on the same substrate. This merging eliminates the need for separate wafers and multiple pick-and-place operations, reducing manufacturing complexity while maintaining color optimization through selective quantum well activation.
Solution Approach 2:
The integrated LED device performs multiple functions (emitting blue, green, and red light) within a single structure. By incorporating multiple quantum well layers with different bandgap energies, the device can selectively emit different colors based on which quantum wells are activated, providing multi-functionality without requiring separate devices.
2Manufacturing precision
If die size decreases to satisfy high resolution requirements, then display resolution improves, but the number of die that must be transferred increases
Solution Approach 1:
By merging multiple color LEDs into a single integrated device, the patent reduces the total number of individual die that need to be transferred and assembled. Instead of transferring separate blue, green, and red die for each pixel location, the integrated device allows for fewer, larger-scale transfers that maintain high resolution while improving productivity.
3Ease of manufacture
If color conversion layers are added to achieve different colors from a single wafer, then manufacturing is simplified, but device complexity and additional processing steps are introduced
Solution Approach 1:
The patent changes the fundamental parameter of light generation by using quantum well bandgap engineering instead of color conversion layers. By adjusting the composition and thickness of quantum well layers during epitaxial growth, different colors are generated directly through electroluminescence, eliminating the need for additional color conversion layers and their associated processing steps.
4Productivity
If multiple quantum well layers are integrated in the same wafer, then the number of epitaxy recipes and pick-and-place operations is reduced, but the complexity of epitaxial growth increases
Solution Approach 1:
The patent segments the epitaxial growth process into distinct sections, each responsible for forming specific quantum well layers for different colors. By organizing the growth process into segmented stages with controlled activation of specific quantum wells, the complexity of growing multiple color layers is managed systematically, enabling single-wafer production of multi-color LEDs.
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 simplifies the manufacturing process, reduces costs and complexity, enhances efficiency, particularly for high drive current densities, and allows for whole wafer-level transfer of pixels onto displays, eliminating the need for separate color conversion layers and reducing the number of pick-and-place operations.
Implementation Method 1
a second mesa first photoluminescent quantum well and a second mesa second photoluminescent quantum well
Implementation Method 2
a first mesa electroluminescent quantum well on a first mesa n-type layer on a substrate
Data Source
AI summary
Described are light emitting diode (LED) devices including a combination of electroluminescent quantum wells and photo-luminescent active regions in the same wafer. A first group of QWs with shortest emission wavelength is placed between the p- and n-layers of a p-n junction. Other groups of QWs with longer wavelengths are placed outside the p-n junction in a part of the LED structure where electrical injection of minority carriers does not occur. Electroluminescence emitted by the first group of QWs is absorbed by other group(s) and re-emitted as longer wavelength light. The color of an individual die made on the wafer can be controlled by either etching away unwanted groups of longer-wavelength QWs at the position of that die, or keeping them intact. Wavelength-selective mirrors that increase down conversion efficiency may be selectively applied to die where longer wavelength emission is desired. The use of tunnel junction contacts facilitates integration of wavelength selective mirrors to external surfaces of the die and avoids problems of conductivity type conversion on etched p-GaN layers.