June 1, 2007 – Researchers from the National Institute of Standards and Technology (NIST), with help from the U. of Maryland and Howard U., have devised a fabrication method that creates tiny ultraviolet light-emitting diodes from nanowires, and NIST says the technique is “well-suited” for scaling to commercial production.
Direct bandgap group III-nitride (AlN/GaN/InN) semiconducting nanowires are seen as promising candidates for small LEDs to be used in sensors, data storage, and optical communications. But making nanowire LEDs typically involves a series of manufacturing techniques that don’t easily translate into commercial production — i.e., crossing n-GaN and p-GaN nanowires, crossing n-GaN and n-Si nanowires, n-GaN core and InGaN/Gan/p-AlGaN/p-GaN multishell structures — “tedious nanowire manipulation methods,” NIST noted — and a series of one-by-one fabrication techniques such as electron-beam lithography and focused ion beam etching.
NIST claims the new GaN LEDs emit a 365nm light wavelength with 25nm full width half maximum FWHM at an applied voltage of 50µA, “squarely in the UV range.” Higher emissions of 385nm were obtained with 65µA injection levels, though possibly due to GaN-oxide interface related recombinations. The UV LEDs also showed “excellent thermal stability” up to 750 degrees C and operational stability after two hours of continuous operation at room temperature.
“The present technique can be applied to other nanowire systems, and is suitable for applications requiring large area nanoscale light sources,” NIST said in its paper. The work from NIST and university researchers was published in the May 29 edition of Applied Physics Letters.