Semipolar MicroLED Assembly for Sub-5 µm Pixel Alignment
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Solution Overview
Problem
Existing methods for manufacturing nitride-based microLEDs face challenges in achieving high resolution and electrooptical performance due to alignment constraints and inefficiencies in radiative efficiency, particularly at reduced pixel pitches and in specific wavelength ranges.
Innovation Solution
A method involving a growth substrate with crystalline layers and angled facets, a semipolar nitride layer, and integrated control circuits allows for precise alignment and reduced dislocation densities, enabling the production of microLEDs with improved performance and reduced pixel pitch, including emission in red and green wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional separate production and placement of control circuit and LED stack is used, then device assembly is simplified, but alignment precision deteriorates leading to inability to achieve pixel pitch less than 5 micrometres
Solution Approach 1:
The patent merges the control circuit and LED array into a single integrated semiconductor structure fabricated using CMOS technology. The control circuit and LED electrodes are formed in the same fabrication process on the same substrate, eliminating the need for separate placement and alignment operations. This integration allows pixel pitches below 5 micrometres to be achieved while maintaining manufacturing simplicity through standard CMOS processes.
2Quantity of substance
If pixel pitch is reduced to increase resolution, then display density improves, but alignment difficulty increases making proper positioning impossible
Solution Approach 1:
The control circuit and LED electrodes are co-fabricated in the same CMOS process, ensuring automatic alignment regardless of pixel pitch. This eliminates alignment errors that would otherwise accumulate at smaller pitch dimensions, enabling high pixel densities to be achieved with proper positioning guaranteed by the integrated fabrication approach.
Solution Approach 2:
The control circuit and LED structures are pre-aligned through the fabrication process itself, where all features are defined by photolithography patterns on the same substrate. This preliminary alignment action during fabrication eliminates the need for post-fabrication alignment operations, ensuring precise positioning even at reduced pixel pitches.
3Ease of manufacture
If standard polar nitride LEDs are used, then manufacturing is straightforward, but radiative efficiency deteriorates especially in red and green wavelength ranges
Solution Approach 1:
The patent changes the crystallographic orientation parameter of the nitride layer from standard polar (001) to semipolar orientations such as (10-11) or (11-22). This parameter change in crystal orientation reduces the quantum confined Stark effect and improves carrier recombination efficiency, thereby enhancing radiative efficiency particularly in red and green wavelength ranges while maintaining compatibility with CMOS fabrication processes.
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 results in microLEDs with enhanced electrooptical performance, reduced dislocation defects, and the ability to produce displays with smaller pixel pitches, improving both the quality and efficiency of nitride-based microdisplays.
Implementation Method 1
a growth substrate including at least one crystalline layer, the crystalline layer comprising a plurality of parallel grooves, each groove comprising at least two angled facets arranged opposite one another, each forming a continuous strip, at least one of said two opposite facets featuring a crystalline orientation {111}
Implementation Method 2
nitride-based microLEDs (light-emitting diodes), the nitride structure comprising: a semipolar layer of nitride, featuring a first face turned towards the crystalline layer, the semipolar nitride layer including a stack comprising at least the first and second semiconducting layers doped for opposite conductivity types
Data Source
AI summary
A method for producing an optoelectronic device having nitride-based microLEDs includes providing an assembly having at least one growth substrate and a nitride structure, where the nitride structure has a semipolar nitride layer that includes an active stack and crystallites extending from facets of the growth substrate with a crystalline orientation {111} to the first face of the semipolar nitride layer and providing an integrated control circuit featuring electric connection pads. The assembly is placed on the integrated control circuit, the growth substrate and the crystallites are removed, and trenches are formed in the stack so as to delimit a plurality of islets, each islet being configured to form a microLED.