New record for UV LEDs
Japanese scientists have developed an aluminum nitride light-emitting diode that emits UV light with a wavelength of 210 nanometers. This is the shortest wavelength that has ever been achieved with LEDs.
While the first highly efficient blue-green light-emitting diodes appeared in the early 1990s, UV LEDs only followed at the turn of the millennium. The main problem for these short-wave light sources is the manufacturing process: Suitable materials contain aluminum, which, however, interferes with the necessary introduction of foreign atoms - the doping - with increasing concentration. Without this change, however, the conductivity of the semiconductor layers is too low - pure aluminum nitride even acts as an insulator. By ingeniously controlling the reaction conditions, the researchers led by Yoshitaka Taniyasu from the Japanese telecommunications company NTT have now succeeded in producing appropriately doped aluminum nitride layers.
In order to use the LEDs on a large scale, however, their light output must be increased a million times and the required voltage of currently 25 volts must be significantly reduced. On the one hand, this means improving the quality of the crystal layers and, on the other hand, making the doping even more efficient.
Currently, mercury, xenon and deuterium lamps are mainly used as UV light sources, but they require high voltage and some of the ingredients are toxic. Since the ozone layer filters out most of the sun's short-wave UV radiation, many organisms have not developed protective mechanisms against it. Irradiation with light of appropriate wavelengths is therefore used to disinfect and kill undesirable bacteria, fungi or viruses.