Multi-Wavelength III-Nitride LED Arrays With Tunnel-Junction Contacts
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Solution Overview
Problem
Current methods for manufacturing microLED displays are inefficient due to the complexity of the pick-and-place process and the difficulty in making ohmic contacts to etched p-GaN surfaces, leading to manufacturing errors and increased costs.
Innovation Solution
The integration of tunnel junctions into the epitaxial layer allows for the formation of LED arrays with independent electrical contacts to n-type GaN layers, eliminating the need for substrate removal and reducing the number of epitaxy recipes, enabling the production of multi-color LEDs on a single wafer with reduced pick-and-place operations and lower operating voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pick-and-place approach is used to assemble microLED displays, then individual microLEDs can be attached to backplane, but the assembly process becomes slow and subject to manufacturing errors
Solution Approach 1:
The patent merges multiple microLEDs of different colors (red, green, blue) into a single integrated microLED die structure. This consolidation eliminates the need for separate pick-and-place operations for each color, enabling the entire microLED array to be transferred as one unit, thereby dramatically improving assembly speed and reducing manufacturing errors.
Solution Approach 2:
The patent segments the microLED structure into distinct functional regions (red, green, blue emitting regions) within a single die, allowing each region to be independently controlled while maintaining a unified transfer process. This segmentation enables full-color display capability without requiring separate assembly steps for each color.
2Ease of manufacture
If pick-and-place approach is used to assemble microLED displays, then individual microLEDs can be attached to backplane, but manufacturing errors increase due to small size and alignment requirements
Solution Approach 1:
By combining multiple color microLEDs into a single integrated die, the patent eliminates the need for precise alignment of separate red, green, and blue microLEDs during assembly. The unified structure ensures consistent positioning and reduces alignment errors that would otherwise occur with multiple separate components.
3Ease of manufacture
If ohmic contacts are made to etched p-GaN surfaces, then electrical connection can be established, but the process becomes difficult and costly
Solution Approach 1:
The patent changes the electrical parameter of the contact region by using heavily doped n-type GaN layers instead of attempting to create ohmic contacts on etched p-GaN surfaces. This parameter change (from p-type to n-type doping, and from low to heavy doping) enables straightforward ohmic contact formation, significantly simplifying the fabrication process and reducing costs.
4Adaptability or versatility
If multiple epitaxy recipes are used to produce different color LEDs, then color diversity can be achieved, but the number of epitaxy recipes increases
Solution Approach 1:
The patent applies local quality by creating different color emitting regions (red, green, blue) within different areas of the same epitaxial wafer. Each region has locally optimized properties (different quantum well compositions and structures) while being grown in a single epitaxy process, thereby achieving color diversity without increasing the number of epitaxy recipes.
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 microLED manufacturing process, reduces costs, and improves efficiency by allowing whole wafer-level transfer of pixels, avoiding the challenges of making ohmic contacts to etched p-GaN surfaces and enabling lower operating voltage and higher wall-plug efficiency.
Implementation Method 1
at least a first LED including a first p-type layer, a first n-type layer and a first color active region and a first tunnel junction on the first LED
Data Source
AI summary
An LED array comprises a first mesa comprising a top surface, at least a first LED including a first p-type layer, a first n-type layer and a first color active region and a tunnel junction on the first LED, a second n-type layer on the tunnel junction. The LED array further comprises an adjacent mesa comprising a top surface, the first LED, a second LED including the second n-type layer, a second p-type layer and a second color active region. A first trench separates the first mesa and the adjacent mesa, cathode metallization in the first trench and in electrical contact with the first and the second color active regions of the adjacent mesa, and anode metallization contacts on the n-type layer of the first mesa and on the anode layer of the adjacent mesa. The devices and methods for their manufacture include a thin film transistor (TFT).