Leti develops smaller-pixel-pitch, highest-resolution microdisplays

Leti developed a micro-LED (μLED) fabrication process to create displays with an 873 x 500 resolution.

Research agency Leti (Grenoble, France), an institute of CEA Tech, has developed a micro light-emitting diode or micro-LED (μLED) fabrication process to create high-resolution arrays at 10-micron pixel pitch. Leti says that the 873 x 500 resolution enabled by the new process exceeds state-of-the-art technology.

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Designed for microdisplay applications such as augmented-reality or virtual-reality tools and wearable devices, the blue or green gallium nitride/indium gallium nitride (GaN/InGaN) µLED arrays use Leti's proprietary self-aligned technology that is key to achieving such a small pixel pitch. A combination of several damascene metallization steps used to create a common cathode is also expected to provide good thermal dissipation and prevent voltage drops within the micro-LED matrix. Electro-optical measurements showcase record efficiency and brightness exceeding requirements for device integration.

The results were presented February 2 at SPIE Photonics West 2017 in San Francisco in a paper entitled "Processing and Characterization of High-Resolution GaN/InGaN LED Arrays at 10-Micron Pitch for Micro-Display Applications."

"Leti's self-aligned process allows the creation of high-resolution µLED matrices with a reduced pixel pitch of 10 µm and paves the way towards even smaller pitches for next-generation devices," said Ludovic Dupré, one of the paper's authors. "In addition, the use of the damascene metallization process of the cathode, which also is a new process developed at Leti, is a breakthrough compared to previous demonstrations of micro-LED matrices. The common cathode indeed fills the whole volume between the micro-LEDs and provides metallic spreading of electrical current between them, as well as thermal dissipation. These results are promising for integrating a micro-LED matrix in micro-display devices by hybridization on CMOS active matrices, and first prototypes are currently being tested."

SOURCE: Sarah-Lyle Dampoux of Mahoney Lyle; http://www.leti.fr/en

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