Technical / research

Lumileds, in collaboration with researchers from the Eindhoven University of Technology have managed to significantly improve the directionality of microLED emission, using metasurfaces.

The researchers embedded a metasurface consisting of nano-sized disks within the p-contact layer of the MicroLED device, and stimulated collective resonances with emitting dipoles in the active region. The enhanced light outcoupling and radiative recombination led to notable improvements in LED efficiency. Additionally, the design of the nanostructure lattice was tailored to manipulate the far-field emission pattern of the LED. The team successfully showed that on-axis candela can be doubled for comparable LED output.

Researchers from the Chinese Academy of Sciences, University of Science and Technology of China and Jilin University developed a novel method for the remote epitaxial growth of continuous crystalline perovskite thin films, that allows for seamless integration into ultrahigh-resolution microLED displays - with pixels less than 5 μm.

The results of their research describe a remote epitaxial growth technique that utilizes a graphene interlayer to create continuous crystalline perovskite thin films over an area of 4 cm². This method effectively eliminates grain boundaries and achieves a pure out-of-plane crystallographic orientation. Using these single-crystalline, freestanding perovskite thin films, the researchers achieved impressive results for micro-LEDs, including electroluminescence efficiency of 16.1%, brightness of 4 × 105 cd m^-2, and ultrahigh resolution with a pixel size of 4 μm.

Researchers from Hong Kong University of Science and Technology (HKUST) have developed a deep-ultraviolt (UVC) microLED display array for use in lithography machines. The researchers say that the array feature enhanced efficiency, and is viable as a source for low cost maskless photolithography.

The researchers, in collaboration with the Southern University of Science and Technology, and the Suzhou Institute of Nanotechnology, have built a maskless lithography prototype platform and used it to fabricate the first microLED device by using deep UV microLED with maskless exposure, improving optical extraction efficiency, heat distribution performance, and epitaxial stress relief during the production process.

Researchers from France's CEA-Leti and CNRS institutes have succeeded in growing highly efficient red, green and blue InGaN submicron microLED nano-pyramids.

The researchers have deposited the nanopyramids by using an MOCVD-based technique, and using nanoselective area growth using an in-situ patterned graphene on SiC as a mask. The researchers report that these microLEDs offer high efficiency with the red microLED offering very regular quantum wells emitting at 620 nm with an In content up to 40%.

Researchers from the Chemnitz University of Technology have combined several new technologies to enable high density high-brightness microLED displays. The researchers demonstrated a 3400 PPI 1080x780 monochrome green display with a brightness of over 10,000,000 nits.

To achieve this high performance display, the researchers used wafer-scale high-quality epitaxial growth, sidewall passivation, efficient photon extraction, and elegant bonding technologies.

Researchers at the Nitride Technology Centre (NTC) at TU Braunschweig, in collaboration with Ostfalia University of Applied Sciences and ams OSRAM, are looking into the use of microLED devices in neuromorphic computing. The researchers say that the adoption of microLED devices may lead to highly efficiency AI computers.

The basic idea is to mimic the biological neural network by using photonic components. The researchers are combining GaN components with conventional silicon microelectronics to create highly integrated arrays with hundreds of thousands of micro-LED. Using microLEDs can enable a power reduction by a factor of 10,000 compared to current technologies. 

Researchers from Korea's Kookmin University have developed a new GaN-based fin-LED chip material and pixel process technology, saying that this innovation may be the key to overcome the limitations of current microLED technologies.

The researchers developed a viable pixel manufacturing process that vertically assembles sub-micron-sized fin-LEDs using a face-selective dielectrophoresis (DEP) assembly method. The GaN-based sub-micron-sized fin-LEDs are designed to maximize performance while minimizing costs related to the chips and pixelation process. This technology significantly enhances extraction light efficiency by vertically aligning the fin-LEDs, and it enables the implementation of chip materials and pixel manufacturing processes that significantly reduce production costs.

Researchers from the KAIST institute in Korea have developed a microLED-based face mask, that aims to slow down skin aging. The researchers say that the mask's flexibility enables uniform light penetration and so can slow down skin aging. The team conducted trials in collaboration with a university hospital, and found out that skin elasticity in the dermal layer improved by 340% compared to conventional LED masks.

Each light mask has 3,770 microLED devices, and a light diffusion layer that disperses the light evenly. The researchers did not detail the size or properties of the microLEDs. The researchers have licensed the technology to FRONICS that plans to commercialize it. 

Researchers from Korea's Kookmin University in Seoul, led by Prof. Young Rag Do, have developed a novel top-down process to fabricate and isolate sub-micron GaN microLEDs. The process combines electrochemical etching and sonochemical separation of the etched porous layer to isolate the microLEDs.

The researchers have used the process to produce Au-coated GaN blue LEDs that offer an EQE of 6.21% (at 4.0 V) and a luminous efficacy of 1,070 cd/m2 (at 10.0 V). The LEDs themselves had a diameter of 750 nm, these are true sub-micon LEDs.

Finland-Based Comptek Solutions announced that it has successfully designed and installed a pilot line that integrates its Kontrox passivation technology with industry-standard techniques like Atomic Layer Deposition (ALD) for substrates up to 200mm. The company says that its technology minimizes surface defects and ensuring an exceptionally high-quality III-V dielectric interface.

The new facility enables Comptek to deliver scalable solutions for a wide range of applications, including power electronics and optoelectronics. One of the key applications for Comptek are microLED devices. Back in 2022, we posted a spotlight on Comptek and a short interview with its CEO, that highlights how the performance of microLED devices is increased thanks to the passivation technology.