Researchers create UV laser out of AlGaN nanowires

February 18, 2019 //By Julien Happich
Researchers create UV laser out of AlGaN nanowires
A team of researchers from the McGill University (Canada) and the University of Michigan (USA) have leveraged the unique properties of Aluminum-Gallium-Nitride (AlGaN) nanowire structures, such as their low defect densities and reduced strain-induced polarization fields, to create a low-threshold photonic crystal ultraviolet laser.

First the researchers used simulation to design and study the properties of a photonic crystal based on AlGaN nanowires. Described in a paper titled “An electrically injected AlGaN nanowire defect-free photonic crystal ultraviolet laser” published in Optics Express, the AlGaN nanowire photonic crystal laser was grown on a sapphire substrate using a site-controlled selective area growth (SAG) process.

Schematic illustration of GaN/AlxGa1-xN multiple
quantum disk nanowire structure and a titled view
SEM image of nanowire arrays.

In selective area growth, the nanowire formation is directly controlled by the nanoscale apertures created on a substrate using a well-defined top-down process. AlGaN nanowire arrays with controlled size and spacing were selectively grown on GaN-on-sapphire template using plasma-assisted molecular beam epitaxy. They were fabricated into photonic crystal lasers using standard photolithography, e-beam lithography, dry etching and contact-metallization techniques. The researchers deposited Ni/Au and Ti/Au metal layers on the nanowire top surfaces and n-GaN template to serve as p-and n-metal contacts, respectively. Because the nanowire structures exhibit nearly identical size distribution, they limit optical scattering losses and do not require any particular mirroring structure.

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