Monolithic RGB Micro-LED Arrays With Fewer Terminals and Mesa Etches
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Solution Overview
Problem
Current monolithic RGB LED arrays face challenges in high-resolution displays due to limited space for mesa etches and terminals, and existing approaches require excessive voltage or filters for color control, leading to inefficiencies in power consumption and color purity.
Innovation Solution
The proposed solution involves a micro-LED array with a reverse polarity structure, where p-GaN is grown before quantum wells, allowing for bias-based control of color emission with fewer terminals and mesa etches, using epitaxial tunnel junctions to integrate multiple emission wavelengths within a single wafer, and a method of manufacturing that includes forming p-n junctions on an epitaxial wafer, bonding a reflective p-contact electrode, and etching for electrical contacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If separate blue, green and red μLEDs are picked and aligned in alternating close proximity on the display, then high-resolution color displays can be produced, but manipulation of microscopic LEDs into the right positions becomes difficult when sizes are in the range of tens of microns or smaller
Solution Approach 1:
The patent combines multiple color LEDs (blue, green, red) into a single monolithic integrated structure with shared substrate and common electrical connections. This merging eliminates the need to manually pick and place separate microscopic LEDs, as they are grown together as one unit, thereby maintaining positioning precision while dramatically improving ease of manufacture.
Solution Approach 2:
The monolithic structure serves multiple functions simultaneously: it integrates multiple color emission regions, provides common electrical connections for multiple LEDs, and uses a shared substrate for mechanical support. This multi-functionality reduces the complexity of assembly while maintaining the precision required for high-resolution displays.
2Ease of operation
If current monolithic RGB array designs are used with at least three biased terminals plus ground connection, then color control is achieved, but limited space available for making all of these mesa etches and terminals makes it difficult to practically implement designs
Solution Approach 1:
The patent merges multiple biased terminals into a single shared terminal structure. Instead of requiring separate terminals for each color LED, the monolithic design allows all color regions to share common electrical connections, thereby reducing the number of terminals from three plus ground to a manageable configuration that fits within the limited pixel space.
Solution Approach 2:
The shared terminal structure performs multiple functions: it provides electrical connection for multiple color regions, serves as a common reference potential, and reduces the overall terminal count. This multi-functional terminal design enables color control while minimizing device complexity and space requirements.
3Device complexity
If one p-n junction with quantum wells of three colors is used, then only two terminals per pixel are required, but excess voltage across the active region is inevitable and filters are required to obtain color characteristics acceptable for displays
Solution Approach 1:
The patent segments the single p-n junction into multiple independent quantum well regions within the same structure. Each color region (blue, green, red) is separated into distinct quantum wells that can be independently controlled, eliminating the excess voltage problem of single-junction designs while maintaining the two-terminal advantage. This segmentation allows selective activation of color regions without requiring filters.
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 reduces the number of terminals required, allows for independent control of emission colors, and achieves lower power consumption while maintaining high color purity and efficiency in micro-LED displays.
Implementation Method 1
the first p-type layer on a first tunnel junction, the second light emitting stack comprises a second electrical contact on a second n-type layer in contact with the first tunnel junction and on a second tunnel junction
Implementation Method 2
a first light emitting stack on a second light emitting stack, the second light emitting stack on a third light emitting stack
Implementation Method 3
light emitting diode (LED) arrays
Implementation Method 4
a reflective p-contact electrode bonded to a backplane
Data Source
AI summary
Provided is a monolithically integrated red green blue (RGB) light emitting diode (LED) array manufactured with a reduced number of mesa etching steps and contact terminals. The LED array may have two or three p-n-junctions grown sequentially on a wafer. One of the p-n junctions has the opposite order of deposition of the n- and p-layers. A light-emitting active region is embedded between the n- and p-layers of each of the p-n junctions. Each active region emits light of different wavelength. The wafer is etched into multi-level mesas, creating two separate voltage terminals and a ground contact to control the bias between particular semiconductor layers. All of the p-n junctions share a common ground contact.