The high-brightness, enhanced-vision systems such as head-up and head-mounted displays can improve safety and performance in fields such as aeronautics and automotive, where the displays allow pilots and drivers to receive key navigation data and information in their line of sight. For consumers, smart glasses or nomadic projection devices with augmented reality provide directions, safety updates, advertisements and other information across the viewing field. LED microdisplays are ideally suited for such wearable systems because of their low footprint, low power consumption, high-contrast ratio and ultra-high brightness.
Leti researchers have developed gallium-nitride (GaN) and indium gallium-nitride (InGaN) LED technology for producing high-brightness, emissive microdisplays for these uses, which are expected to grow in the next three to five years.
“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.”
Announced during Display Week 2015 in San Jose, California, USA, Leti’s technology innovation is based on micro-LED arrays that are hybridized on a silicon backplane. Key innovations include epitaxial growth of LED layers on sapphire or other substrates, micro-structuration of LED arrays (10 μm pitches or smaller), and 3D heterogeneous integration of such LED arrays on CMOS active-matrices.
The innovations make it possible to produce a brightness of 1 million cd/m² for monochrome devices and 100 kcd/m² for full-color devices with a device size below one inch and 2.5 million pixels which is a 100- to 1,000-times improvement compared to existing self-emissive microdisplays, with good power efficiency. The technology also will allow fabrication of very compact products that significantly reduce system-integration constraints.
The high-density micro-LED array process was developed in collaboration with III-V Lab.
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