Fabrication pathway for high-density micro-LED arrays showcased

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 GaN and InGaN LED technology for producing high-brightness, emissive microdisplays for these uses, which are expected to grow dramatically in the next three to five years. For example, the global research firm MarketsandMarkets forecasts the market for HUDs alone to grow from $1.37bn in 2012 to $8.36bn in 2020.

Announced during Display Week 2015 in San Jose, Leti’s technology 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 1m cd/m² for monochrome devices and 100,000cd/m² for full-colour devices with a device size below 1" and 2.5m pixels. This is a 100- to 1,000-times improvement compared to existing self-emissive microdisplays, with very good power efficiency. The technology also will allow fabrication of very compact products that significantly reduce system-integration constraints.

“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 Optics and Photonics Department, Leti. “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.”

The high-density micro-LED array process was developed in collaboration with III-V Lab.