Leti develops CMOS-driven micro-LEDs with simplified transfer process that eliminates TFT backplane

On 14 May during Display Week 2019 in San Jose, CA, USA, micro/nanotechnology R&D center CEA-Leti of Grenoble, France has presented a paper on new technology for fabricating high-performance gallium nitride (GaN) micro-LED displays for applications ranging from smart watches to TVs with no size limit.

The approach fabricates elementary units of all-in-one red, green, blue (RGB) micro-LEDs on a CMOS driving circuit, and transfers the devices to a simple receiving substrate. The units are fabricated with a full semiconductor, wafer-scale approach.

“This new process, in the proof-of-concept stage, paves the way to commercial, high-performance micro-LED displays,” reckons François Templier, CEA-Leti’s strategic marketing manager for photonic devices. “The CMOS-based approach provides higher-brightness and higher-resolution micro-LEDs and is a game changer for very large TVs,” he adds.

While they promise exceptional image quality and better energy efficiency than existing liquid crystal display (LCD) and organic light-emitting diode (OLED) technologies, micro-LED displays currently face significant barriers to commercialization.

One of the biggest challenges is improving the performance of the driving electronics, which require more power to deliver brighter images and more speed to support continuously increasing demands for high display resolution. Faster electronics are required to power millions of pixels in a fixed-frame time in micro-LED displays, but existing thin-film transistor (TFT) active-matrix driving display technology cannot provide the necessary current and speed.

CEA-Leti’s new approach fabricates CMOS-driven, high-performance GaN micro-LED displays with a simplified transfer process that eliminates the use of the TFT backplane. RGB micro-LEDs are stacked directly onto a micro-CMOS circuit, and each unit is transferred onto a simple receiving substrate. Then, the RGB micro-LEDs and the backplane are fabricated on a single semiconductor line.

In addition to increasing power and driving speed – and improving display performance – this process avoids several costly steps needed with existing technology to make electrical and mechanical contacts between micro-LEDs and the receiving substrates.

Tags: GaN-on-Si microLED

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