Flexible microLED uses graphene and GaN

Flexible microLED uses graphene and GaN

Technology News |
By Nick Flaherty

Researchers from the US and Korea have used graphene to create a microLED array of GaN that can be folded, twisted, cut and stuck to different surfaces.

The researchers at the University of Texas at Dallas used a non-stick layer of graphene on a sapphire substrate to release the microLED array. The array is constructed using epitaxy to build vertical microrods of gallium nitride (GaN). The array is then transferred to a flexible copper sheet.

“The biggest benefit of this research is that we have created a detachable LED that can be attached to almost anything,” said Dr. Moon Kim, professor of materials science and engineering at UT Dallas and a corresponding author of the study. “You can transfer it onto your clothing or even rubber, that was the main idea. It can survive even if you wrinkle it. If you cut it, you can use half of the LED.”

The researchers in the Erik Jonsson School of Engineering and Computer Science and the School of Natural Sciences and Mathematics in Texas worked with colleagues in South Korea who carried out laboratory tests of LEDs by adhering them to curved surfaces, as well as to materials that were subsequently twisted, bent and crumpled. In another demonstration, they adhered an LED to the legs of a Lego minifigure with different leg positions.

“The graphene does not form chemical bonds with the LED material, so it adds a layer that allows us to peel the LEDs from the wafer and stick them to any surface,” said Kim, who oversaw the physical analysis of the LEDs using an atomic resolution scanning/transmission electron microscope at UT Dallas’ Nano Characterization Facility.

Bending and cutting do not affect the quality or electronic properties of the LED, said Kim.

The flexible microLED array can be used for flexible lighting, clothing and wearable biomedical devices. From a manufacturing perspective, the fabrication technique offers another advantage: Because the microLED array can be removed without breaking the underlying wafer substrate, the wafer can be used repeatedly.

“You can use one substrate many times, and it will have the same functionality,” Kim said. In ongoing studies, the researchers also are applying the fabrication technique to other types of materials. “It’s very exciting; this method is not limited to one type of material,” he added. “It’s open to all kinds of materials.”

The research was funded in part by the National Research Foundation of Korea, the Korea Institute for Advanced Technology and the U.S. Department of Energy.

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