Leti demos process to make micro-LED Arrays for wearable vision
French research organisation CEA-Leti has demonstrated a path to fabricating high-density GaN and InGaN micro-LED arrays for next generation wearable and nomadic vision systems. The process is said to be scalable to the IC manufacturing process.
Head-mounted and head-up displays for aeronautics and automotive applications, and smart glasses with augmented reality for consumers, are expected to grow dramatically in the next three to five years. Research firm MarketsandMarkets forecasts the market for head-up displays alone to grow from $1.37 billion in 2012 to $8.36 billion in 2020.
Announced during Display Week 2015 in San Jose, California, Leti's innovation is based on micro-LED arrays that are hybridised on a silicon backplane. Key innovations include epitaxial growth of LED layers on sapphire or other substrates, micro-structuration of LED arrays (10µm pitches or smaller), and 3D heterogeneous integration of such LED arrays on CMOS active-matrices.
These innovations make it possible to produce a brightness of 1 million cd/m2 for monochrome devices and 100 kcd/m2 for full-colour devices with a device size below one inch and 2.5 million pixels. This is a 100- to 1,000-times improvement compared to existing self-emissive microdisplays, with very good power efficiency, according to Leti. The technology should also allow fabrication of compact products that reduce system-integration constraints.
The high-density micro-LED array process was developed in collaboration with III-V Lab, a private R&D organisation jointly established by Alcatel-Lucent and Thales in 2004 under the French 'Economic Interest Group' (GIE) status.
LED microdisplays are suited for such wearable systems because of their low footprint, low power consumption, high-contrast ratio and ultra-high brightness, says Leti. "Currently available microdisplays for both head-mounted and compact head-up applications suffer from fundamental technology limitations that prevent the design of very low-weight, compact and low-energy-use products," said Ludovic Poupinet, head of Leti's Optics and Photonics Department.
"Leti's technology breakthrough is the first demonstration of a high-brightness, high-density micro-LED array that overcomes these limitations and is scalable to a standard microelectronic large-scale process. This technology provides a low-cost, leading-edge solution to companies that want to target the fast-growth markets for wearable vision systems," he added.
