May 19, 2017: With the aim to create ultra-bright LEDs, the Grenoble-based research institute CEA LETI (LETI), is now transforming nanowire technology, which was first designed for transistors. At present the market consists of three types of MOSFET designs which include nanowire technology, fin field effect transistor (FinFET), and a fully depleted-silicon on insulator (FD-SOI) MOSFET.
The industry still mostly uses silicon-based technology, hence there is the need to justify and convince them to opt for new materials, according to a LETI spokesperson.
3D GaN nanowires
III-V group semiconductor materials like GaN offers better performance in optical applications and driver, the spokesperson added. Silicon-based nanowires were actually created for transistor applications. However, in 5-7 nanometer sized applications LETI is using 3D GaN nanowires for lighting applications.
GaN nanowire 3D LEDs are extremely bright, and can reach 107 nits, whereas OLEDs typically are capable of lighting 10,000 nits, according to LETI. LETI’s 3D GaN LEDs are nearly 10 times brighter than another Université Grenoble Alpes, another research institute based in France.
Due to their wave guiding properties, nanowires can facilitate light extraction in LEDs, according to research by Université Grenoble Alpes. As compared to conventional 2D LEDs, 3D GaN nanowire LEDs has ess droop, and is also capable of placing a variety of color LEDs onto the same wafer or chip.
Some challenges ahead
When working with GaN substrates, some challenges may come up which include quality of the buffer, patterning of the epitaxy layer, epitaxy and ensuring that the epitaxies are defect free to optimize light adaptation. For example, LETI’s diamond display uses patterned GaN epiwafers rather than a thin epiwafer layer.
However, GaN LEDs are fully compatible with displays and integration onto silicon wafers, added the LETI spokesperson. Further she said that the GaN LED also needs to be stacked to control each individual nanowire LED to offer excellent electrostatic control.