Introduction

Micro Light Emitting Diodes (MicroLEDs), an emerging flat-panel display technology, have been gaining significant attention in the tech world. 

With a forecasted value of $56.00 million in 2020 and a compound annual growth rate (CAGR) of 77.1% from 2021 to 2030, the global micro-LED display market is expected to reach $23.4 billion.

However, the journey of Micro LED technology is not just about the technology itself but also about the intellectual property that protects and propels it. 

A recent report analyzed over 1000 granted or published patent applications on Micro LED displays. Nearly 5,500 patents in µLED technology had been filed by over 350 different organizations as of the end of the previous year; about 40% of the patent applications were filed in 2019 alone.

These patents are the silent markers of progress, each representing a step forward in the ongoing evolution of MicroLED research technology. This article aims to spotlight the current projects in MicroLED research with a particular focus on patents.

Current State of MicroLED Research

MicroLED research technology considered the next generation of display technology, has been the focus of extensive research and development. It offers several advantages, such as high miniaturization, thin film and integration, high brightness, high contrast, fast response speed, and long service life. However, there are still some technical and cost challenges that need to be addressed. 

Recent Developments in MicroLED Technology

Some of the recent advancements in MicroLED research are:

1. Chip Technology: Researchers have been focusing on key technologies involved in MicroLED display technology, such as chip technology, mass transfer, full-color display, bonding, and driving technology. For chip epitaxy technology, the emphasis is on wavelength uniformity, current density, and defect control.
2. High Pixel Density Displays: In 2023, researchers from Massachusetts Institute of Technology and other universities in the United States and South Korea achieved a vertical full-color Micro-LED array with the highest pixel density (5100 PPI) and the smallest chip size (4 μm) reported so far. This development is crucial for augmented/virtual reality (AR/VR) applications, which require high efficiency, small size, and ultra-high resolution displays.
3. Integration of Metasurface Structures: Researchers have been integrating metasurface structures with Micro-LEDs to improve their performance. Metasurfaces can modulate the wavefront of light, and by exploiting this capability, researchers have achieved many excellent results, including improving the light extraction efficiency, controlling the emission angle to achieve directional emission, and obtaining polarized Micro-LEDs.
4. GaN LED Technology: Solid-state lighting technology based on gallium nitride (GaN) has completely transformed the semiconductor market. GaN technology has made reducing the carbon footprint and global energy consumption possible. Thanks to recent advancements, GaN is no longer just used for lighting; micro-LEDs, laser projection, and point sources have also been developed. 
5. Non-Polar and Semi-Polar LEDs: Scholars worldwide are focusing on III-N materials in an effort to advance current technologies and extend the boundaries of the III-V domain. Currently, research is being done to increase the efficiency of non-polar and semi-polar generated LEDs.

Challenges and Solutions in the Field

Despite having numerous advancements, certain challenges need to be addressed in MicroLED research:

1. The efficiency of MicroLEDs: Conventional LEDs can reach external quantum efficiencies (EQEs) to ~70 percent, while tiny microLEDs less than 10µm may struggle to reach 20 percent. With low EQEs and fragile characteristics, red LEDs present particular challenges. Researchers are working on improving the efficiency of MicroLEDs through various methods, such as optimizing the chip design and manufacturing technique.
2. Mass Transfer: The process of transferring the microLEDs onto the display backplane is a significant challenge due to the sheer number of LEDs involved. Days or even weeks may pass during this procedure. Many techniques are being tested, including roller transfer, fluid assembly, elastomer and electrophotographic transfer, and so on.
3. Inspection and Repair: The biggest challenge in manufacturing is the individual verification of each LED to identify failed units that are replaced using specialized pick-and-place equipment. This test and repair process may take several hours.
4. Integration with Silicon-Based Devices: Integrating compound semiconductor microLEDs with silicon-based integrated circuit devices with very different material properties and fabrication processes is another challenge.
5. Color Conversion: Developers are working to address challenges such as color conversion. They are investigating whether adding quantum dots could simplify the manufacturing process.
6. Size Limitations: Smaller pixel spacing is another production difficulty brought on by the physical size constraints of related electronics. The maximum size of a microLED display’s total dimensions is determined by this constraint.

Patent Analysis in MicroLED Research Technology

The patent landscape in MicroLED research technology is vast and dynamic, reflecting the rapid advancements and high level of interest in this field. A detailed analysis of this can provide valuable insights into the current state of technology, key players, and future directions.

Overview of the Patent Landscape

In recent years, nearly 5,500 patents in MicroLED research technology have been filed by more than 350 different organizations.

However, the first patents were filed around 2000 or 2001. As a result, the number of issued patents is still quite small.

Detailed Analysis of Key Patents

Some of the detailed analyses of the patents are:

1. Patent US10636349B2: Micro LED display device and method of fabricating the same
   This patent, granted to Lumens Co Ltd, discloses a micro light emitting diode (LED) display device capable of implementing a full color of high resolution. The device includes a micro LED driving substrate (backplane) in which a plurality of CMOS cells are arranged in rows and columns and a microLED panel that is flip-chip bonded onto the micro LED driving substrate. The microLED panel includes the plurality of micro LED pixels formed by etching the first surface of an emission structure along a unit pixel region.
2. Patent WO2019027820A1: Nanoporous micro-led devices and methods for making

LED devices with gallium nitride LED diodes that have at least some of their color-converting quantum dots added are provided by this invention. Additionally, the invention offers techniques for creating LED gadgets. The LED gadget consists of many Gallium-Nitride (GaN) diodes placed on the semi-conductive surface, an array of electrical circuits set up to enable individual electronic control of each circuit, and a semi-conductive surface.

End Note

MicroLED research is booming, with breakthroughs in pixel density and metasurface integration. However, hurdles persist in efficiency, mass transfer, and silicon chip integration. Future efforts should target improved efficiency, especially for red LEDs, faster mass transfer methods, automated defect repair systems, seamless microLED-silicon integration, exploring quantum dots for color conversion, and overcoming miniaturization limitations. By tackling these challenges, microLEDs are poised to revolutionize displays.