In many application fields, there is a growing market demand for high quality information displays. This is true in commercial avionics where high luminance displays able to provide readable information in a very bright environment are expected. Nowadays, the existing technologies do not allow the manufacturing of displays emitting the desired brightness (>50,000 cd/m2 white light) at low power consumption and in a compact volume. This is why the HiLiCO project implemented in the framework of the Clean Sky 2 programme aims at developing a new generation of very bright monochrome and full-colour GaN micro-displays with high pixel resolution (WUXGA), and good form factor capabilities. It should enable the design of ground breaking compact see-through systems for next generation avionics applications.
To achieve this goal, the HiLICO project addresses numerous technical topics: (i) development of high-quality GaN based LED epilayers, (ii) design and fabrication of a dedicated CMOS matrix (ASIC) to control each individual pixel, (iii) coupling of the LED structure to the CMOS matrix followed by high precision LED pixelisation (9.5 µm pixel pitch), (iv) transfer on blue emitting devices of dedicated light conversion layers to manufacture bi- or full-colour display demonstrators and (v) manufacturing and testing of LED microdisplay demonstrators.
Among these objectives, four of them have been achieved with very significant progress. The technical results have demonstrated performances that match and sometimes exceed the existing state of the art. This is the case for the GaN epilayer EQE, the HILICO ASIC capabilities, the microLED display technology and the red conversion efficiency. For the last objective (demonstrators), the results obtained so far constitute a solid working basis for further development of colour LED microdisplays.
In terms of impact, compared to existing LCD technologies, the LED technology offers not only higher luminance and contrast but also potential higher energy efficiency. We estimate that at long term, its energy efficiency could reach 6%, twice the efficiency of LCD microdisplays. Beyond the reduced environmental impact, another benefit is clearly the enhanced aircraft safety with more readable information. Finally, the HILICO developments will contribute to the building of a new LED microdisplay industry since, beyond avionics, new application fields have recently emerged as optical wireless communications or health applications.
