With wavelengths of between 200 and 280nm, deep-UV mercury-based lamps are known for killing harmful organisms, such as viruses, bacteria, mould and dust mites, by penetrating their membranes and attacking their DNA. The mercury-based lamps, however, pose a threat to the environment, and are bulky and inefficient.

"UV-C light applications are attractive because deep-UV light can destroy the DNA of species that cause infectious diseases, which cause contamination of water and air," explained Postdoctoral researcher Moudud Islam.

To counter this problem, a research group from the Cornell University and the University of Notre Dame is currently working on developing an LED-based solution.

Using atomically controlled thin monolayers of gallium nitride (GaN) and aluminium nitride as active regions, the group has shown they can produce deep-UV emissions between wavelengths of 232 and 270nm with a LED.

According to the team, the 232nm emission represents the shortest recorded wavelength using GaN as the light-emitting material.

One of the major challenges with ultraviolet LEDs is efficiency, which is measured in three areas: injection efficiency – the proportion of electrons passing through the device that are injected into the active region; internal quantum efficiency (IQE) – the proportion of all electrons in the active region that produce photons; and light extraction efficiency – the proportion of photons generated in the active region that can be extracted from the device.

In the deep-UV range, all three efficiency factors suffer, but the researchers found that by using gallium nitride instead of conventional aluminium gallium nitride, both IQE and light extraction efficiency are enhanced.

Injection efficiency is also improved through the use of a polarisation-induced doping scheme for both the negative and positive carrier regions.