UV/DUV Light Emitters
Solid-state UV/DUV light emitters with wavelengths from 400 nm down to 200 nm are the fundamental building block for several key applications. Polymer curing, air-water purification, bio-medical instrumentation, gas sensing, and germicidal systems are examples of these. Such systems are critically important for many industrial applications, and for improving quality of life and the mitigation of public health challenges posed by viruses, e.g. causing COVID-19. Despite significant progress and commercialization of UV/DUV light emitters, numerous challenges remain, and they have become the catalyst for the ongoing research. The light output power, external quantum efficiency, operation voltage, and long-term stability of UVB/C LEDs is still not to the level of their visible wavelength counterparts. Critical challenges include low resistance UV-reflective contacts as well as efficient carrier injection which can be addressed by novel approaches like tunnel-junctions and polarization doping. Technique such as laser liftoff coupled with backside shaping for enhanced light extraction are more difficult to incorporate in UVB/C LEDs with high-Al composition AlGaN layers. Recently several groups have reported laser diodes in the UVB/C spectral region. But the demonstrated devices are still a long way from what is needed for practical systems. Some initial reports of n- and p-type doping of AlN also open exciting possibilities for devices with emission wavelengths down to 210 nm.
Guest Editors: Asif Khan, Michael Kneissl, and Hiroshi Amano