A path to fabricating high-density micro-LED arrays has been demonstrated by CEA-Leti for next generation wearable and nomadic systems. It is a process that is scalable to the IC manufacturing process.
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 suited for 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 dramatically in the next three to five years. For example, MarketsandMarkets forecasts the market for head-up displays will grow from $1.37 billion in 2012 to $8.36 billion by 2020.
See-through HMD provides the visual superposition of the real-world environment and displayed information. These smart glasses require components such as microdisplays with OLED or microLED and advanced optics with a large field of view.
The 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 pitch 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-color 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. 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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