Sapphire

Researchers from Korea's Seoul National University and Sungkyunkwan University developed a method to grow GaN LED arrays on a flexible graphene layer. The so-called microdisks arrays exhibit excellent crystallinity with a uniform in-plane orientation and strong blue light emission. 

The researchers grew the GaN microdisks on a graphene layer (grown on a sapphire substrate) covered with a micro-patterned SiO2 mask using metal–organic vapor-phase epitaxy. The microdisks were then processed into micro-LEDs and then successfully transferred onto bendable substrates. 

Coherent manufactures several key AR display components and is actively working to improve the technology.

This is a sponsored message by Coherent

Virtual reality (VR) and augmented reality (AR) have received a lot of media buzz over the past few years. They promise benefits for applications are as diverse as gaming, healthcare, training, engineering, architecture, interior design, travel, defense, and even product marketing. But today, VR/AR still hasn’t had a significant impact on most people’s lives.

Two main reasons for this are VR/AR headset quality and cost. Specifically, quality includes factors like image brightness, resolution, field-of-view, and electronic characteristics like speed and power consumption. Plus, practical considerations, including headset size, weight, and battery lifetime are also important. And cost means bringing down headset prices low enough to make them accessible to most consumers.

We're happy to interview Coherent, as part of our series of interviews with MicroLED Industry Association members. Coherent is one of the world's leading laser innovators and manufacturers, providing systems and components for the production of OLED and microLED displays.

Q: Can you introduce your company and technology?

Oliver Haupt, Director, Marketing, Display Vertical, Coherent Corp: For over 50 years, we have been providing high-performing, reliable photonics-based solutions that have become the enabling tool in many applications. Today, Coherent Corp. is one of the world’s leading photonics innovators and manufacturers.

Displays are getting larger and more interactive in our homes and cars. State-of-the-art displays are slim, bendable, and high-resolution, with a wide color gamut. Future displays will range in size from tiny ones for AR/VR applications, to more than 100-inch in diagonal for very large wall TVs.

Researchers from the US and Korea, led by MIT, developed full-color vertically-stacked microLEDs that achieve the highest array density (5100 PPI) and the smallest size (4 µm) reported to date.

To end up with such high resolution and small microLED chip size, the researchers used a 2D materials based layer transfer (2DLT) technique. The resulting microLEDs, that have near-submicron thickness, are grown on 2D material-coated substrates, removed, and then stacked.

Stacked-RGB microLED microdisplay developed Sundiode announced that it has achieved the successful growth of a monolithic, all-InGaN RGB LED structure on a single sapphire wafer. This structure was developed in collaboration with Soft-EPI.

Sundiode's epitaxial technology enables stacked-RGB LEDs with multiple junctions, capable of emitting RGB colors independently. This structure makes it easier to produce ultra-high density microdisplays.

Germany-based 3D-Micromac is the industry leader in laser micromachining and roll-to-roll laser systems. The company develops and manufactures processes and laser systems delivering powerful, user-friendly and leading-edge processes with superior production efficiency. 3D-Micromac offers industrial laser solutions for the mass production of microLED displays.

We had the pleasure of talking to Frank Richter, Head of Sales and Product Management at 3D-Micromac. Frank explained 3D-Micromac's solutions and technologies for microLED production, and the company's views on the future of microLEDs.

Q: Can you detail 3D-Micromac's solutions for the MicroLED market?

Frank Richter, Head of Sales and Product Management: 3D-Micromac’s product portfolio includes several laser-based system solutions for various manufacturing steps in the MicroLED production process. All systems offer an integrated process control and monitoring to assure stable and reliable operation thus enabling high throughput and low yield losses.

This is an article by TechBlick, organizers of the upcoming MicroLED Displays virtual event. MicroLED-Info readers get a 100 Euro discount.

In this article, using select technology slides, we highlight several interesting advancements in MicroLED and/or QD displays. More specifically, we cover 3600PPI “Silicon” Displays | Gravure printed microbumps | Electrohydrodynamically printed QD color converters | Laser LLO and Transfer for MicroLEDs | QD vs Phosphors | Energy saving credentials of microLED

“Silicon” Displays with an incredible 3600ppi full color using microLED and QD technology?

Sharp (HIRANO Yasuakie et al) has developed this technology.

As shown in the slide below, first blue-only uLEDs are formed on a sapphire substrate. Here, one LED array contains 352 x 198 micro LED dies of 24 um x 8 um in size. In parallel, an LSI chip containing the driving circuitry is formed on a silicon wafer. Here, the cathode (N-type electrode) and anode (P-type electrode) are fabricated for each micro LED die to apply driving voltage independently to each die. The Au bump electrodes are fabricated in accordance with the pitch of the LED dies. The two substrates are flip-chip bonded using Au-Au bonding. Here one can already see the parallel to the silicon and optoelectronic industry (vs. the traditional thin film display industry!). Next, the sapphire layer is removed via laser lift off. Finally, Cd-free quantum dots (green and red) are deposited atop the microLED dies to enable R G color conversion. This way one achieves RGB colors.

China-based GaN epiwafer producer Enkris Semiconductor launched new microLED epiwafers. The "Full Color GaN" series offers GaN-on-Si microLED epiwafers, with wafers sizes of up to 300 mm.

Enkris' new epiwafers offers blue, red and green LED arrays, all based on the same material platform. Enkris Semiconductor uses its patented strain engineering and polarization engineering, which it says is unique, to expand its GaN-on-Si LED epiwafer product portfolio to all colors (with wavelengths of 390-650nm).

This is a sponsored post by Coherent

Coherent is a leading global supplier of lasers and photonics technology. For the MicroLED industry, Coherent provides several solutions from a single laser source, optical systems up to an integrated system for the three vital processes in MicroLED fabrication – Laser Lift-Off (LLO), Laser-Induced Forward Transfer (LIFT), and Repair/Trimming.

Coherent recently published a new white paper that provides an update on how high-energy ultraviolet laser beams enable LLO and LIFT processes. The white paper shows the importance of a perfect combination of laser and optical design to a how these lasers ensure placement accuracy and mass transfer that will remain future-proof as microLED chip die size continues to shrink.

The founder and General Manager of Bolite Optoelectronics, Dr. Bowen Cheng, was invited to present at the recent Touch Taiwan 2021 Conference in April. The title of his talk was “Laser Processing Applications for the Manufacturing of Mini and MicroLED Displays.” Since it was presented in Mandarin only, microled-info.com caught up with Dr. Cheng to learn more about this trending subject and the company he started.

Q: Dr. Cheng, can you please tell us a little about your background, prior to starting Bolite?

I was a research engineer at Xerox PARC and helped develop surface micromachined microspring interconnects in a project funded by the U.S. Army Research in collaboration with Oracle. I was also a vital member of the team that successfully demonstrated the world's shortest wavelength diode laser at the time, a 250 nm UV laser for military applications. With these experiences in both semiconductor laser processing and MEMS processing, I decided to start Bolite and build a team to develop state-of-the-art laser solutions for microprocessing applications.

Q: I must admit I’ve not heard of Bolite before. What differentiates you from other laser microprocessing companies?