New ultraviolet LED for portable, low-cost devices developed

WASHINGTON: Researchers have developed a new ultraviolet (UV) light-emitting diode that could lead to more portable and low-cost devices.

The patent-pending LED creates a more precise wavelength of UV light than today's commercially available UV LEDs, and runs at much lower voltages and is more compact than other experimental methods for creating precise wavelength UV light.

The LED could lend itself to applications for chemical detection, disinfection, and UV curing. With significant further development, it might be able to provide a source for UV lasers for eye surgery and computer chip manufacture.

Ohio State University engineers created LEDs out of semiconductor nanowires which were doped with the rare earth element gadolinium.

The unique design enabled the engineers to excite the rare earth metal by passing electricity through the nanowires, said study co-author Roberto Myers, associate professor of materials science and engineering at Ohio State.

Doctoral students Thomas Kent and Santino Carnevale utilised another patent-pending technology they had helped develop - one for creating nanowire LEDs.

On a silicon wafer, they tailor the wires' composition to tune the polarisation of the wires and the wavelength, or colour, of the light emitted by the LED.

Gadolinium was chosen not to make a good UV LED, but to carry out a simple experiment probing the basic properties of a new material they were studying, called gadolinium nitride.

During the course of that original experiment, Kent noticed that sharp emission lines characteristic of the element gadolinium could be controlled with electric current.

Different elements fluoresce at different wavelengths when they are excited, and gadolinium fluoresces most strongly at a very precise wavelength in the UV, outside of the range of human vision. The engineers found that the gadolinium-doped wires glowed brightly at several specific UV frequencies.

The team showed that in a nanowire LED structure, the same effect can occur, but at far lower operating voltages: around 10 volts.

High voltage devices are difficult to miniaturise, making the nanowire LEDs attractive for portable applications.

The study was published in the journal Applied Physics Letters.