Monolithic RGB MicroLED Array with Mesa-Pyramid Pixel Structures
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Solution Overview
Problem
Existing microLED fabrication techniques face challenges such as the need for stacking and bonding multiple wafers, which can lead to damage to microLED sidewalls and affect the performance of the LEDs.
Innovation Solution
The method involves fabricating monolithic red/green/blue microLED pixel arrays using epitaxial growth on a semiconductor wafer template, which includes forming mesa and pyramidal structures with specific MQW layers and p-GaN layers to achieve efficient light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If multiple wafers are stacked and bonded to fabricate microLED arrays, then the complexity of the fabrication process is reduced, but the microLED sidewalls are damaged and performance deteriorates
Solution Approach 1:
The invention segments the fabrication process into two distinct stages: first, growing separate color microLEDs (red, green, blue) on individual GaN wafers using MOCVD; second, transferring and bonding these pre-formed microLEDs to a carrier substrate in a 3x3 array configuration. This segmentation allows each microLED to be optimized independently before assembly, avoiding the damage that would occur from stacking multiple wafers while maintaining the benefit of integrated array fabrication.
2Manufacturing precision
If monolithic polychromatic microLEDs are fabricated using epitaxial growth, then the manufacturing precision and quality are improved, but the device complexity increases
Solution Approach 1:
The invention applies local quality by growing different colored microLEDs (with different material compositions and structures) on separate GaN wafers using MOCVD, where each wafer is optimized for its specific color. The red, green, and blue microLEDs have distinct quantum well structures and indium compositions tailored to their respective wavelengths. This localized optimization ensures high manufacturing precision for each color while avoiding the complexity of attempting to grow all colors monolithically in a single structure.
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 allows for the fabrication of high-efficiency, monolithic polychromatic microLEDs at a wafer scale, potentially improving the performance and reducing the damage to microLED sidewalls compared to conventional methods.
Implementation Method 1
fabricating monolithic red/green/blue microLED pixel arrays using epitaxial growth on a semiconductor wafer template
Implementation Method 2
forming a mesa and a pyramid, each including a multiple quantum well (MQW) layer and a p-type GaN (p-GaN) layer... configured to emit light
Data Source
AI summary
A light emitting diode (LED) pixel array and method of fabrication thereof. A semiconductor wafer template includes a dielectric layer formed over a lower n-type gallium nitride (n-GaN) layer. A first aperture and a second aperture are formed through the dielectric layer and extending to the lower n-GaN layer, the second aperture being narrower than the first aperture. A mesa is formed within the first aperture by successively forming a mesa n-GaN layer, a mesa MQW layer above the mesa n-GaN layer, and a mesa p-GaN layer above the mesa MQW layer. A pyramid having sidewalls is formed within the second aperture by successively forming a pyramidal n-GaN layer, a pyramidal MQW layer, and a pyramidal p-GaN layer. The mesa n-GaN layer, mesa MQW layer, and mesa p-GaN layer form a mesa LED. The pyramidal n-GaN layer, pyramidal MQW layer, and pyramidal p-GaN layer form a pyramid LED.