UV LEDs grown on graphene: ten times more efficient, cheaper and flexible

February 08, 2019 //By Julien Happich
UV LEDs grown on graphene: ten times more efficient, cheaper and flexible
Founded in June 2012 as a spin-off from the Norwegian University of Science and Technology (NTNU), startup CrayoNano AS promises UV-A LEDs (emitting at 365nm) with 10 times the efficiency of existing deep UV LEDs at a tenth of the cost, thanks to graphene.

The company CTO and co-founder and also professor in nano-electronics & nano-photonics at the Norwegian University of Science and Technology, Dr. Helge Weman co-authored a paper comforting all these claims.

The paper “GaN/AlGaN Nanocolumn Ultraviolet Light-Emitting Diode Using Double-Layer Graphene as Substrate and Transparent Electrode” published in the Nano Letters describes how a multi-disciplinary team of Norwegian and Japanese researchers leveraged the unique properties of atomic-thin layers of graphene as a hexagonal lattice template for the nucleation and growth of perfectly crystalline GaN/AlGaN nanowires (with less than 2% of lattice mismatch). Standing vertically on their graphene substrate (on top of amorphous silica), the 220nm diameter nanocolumns exhibit near-perfect hexagonal cross-sections and their growth is so perfectly controlled by radio frequency plasma-assisted molecular beam epitaxy (RF-PAMBE) that they all have the same average height, making it easy to cap them with a planar electrode. The growth process is fast too, with nanowires reaching a 1µm height within minutes.

Being transparent in all parts of the electromagnetic spectrum including the whole UV region, graphene offers an excellent alternative to indium tin oxide as the top-emitting transparent conductive electrode (TCE) for GaN and InGaN LEDs, the authors write. Another benefit of graphene is its extreme thinness and flexibility.

Fabricating a flip-chip UV LED device based on RF-PAMBE grown GaN/AlGaN nanocolumns on a double layer graphene/silica glass substrate.

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