Designed for micro-display applications such as augmented-reality or virtual-reality tools and wearable devices, the blue or green GaN/InGaN µLED arrays use Leti’s proprietary self-aligned technology.
That process is key to achieving such a small pixel pitch. A combination of several damascene metallisation 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 on 2nd February at SPIE Photonics West in San Francisco in a pape entitled Processing and Characterisation of High-Resolution GaN/InGaN LED Arrays at 10μ Pitch for Micro-Display Applications.
“Leti’s self-aligned process allows the creation of high-resolution µLED matrices with a reduced pixel pitch of 10µm 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 metallisation 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 hybridisation on CMOS active matrices, and first prototypes are currently being tested.”
