Deep-ultraviolet (DUV) light is used for sterilization, assisting chemical reactions, and photolithography. The disadvantages of conventional DUV sources such as excimer lasers and mercury-vapor lamps—expense and inclusion of toxic substances—are driving researchers to create more efficient DUV LEDs. Aluminum gallium nitride (Al-GaN) shows promise as an active material for DUV LEDs, but the efficiency of AlGaN LEDs emitting at wavelengths below 300 nm has remained low.
A group of scientists from Stanley Electric Corporation and the National Institute of Advanced Industrial Science and Technology, Osaka University, Shizuoka University, and Nagoya University (all in Japan) has created a DUV LED that contains both AlGaN quantum wells and graphene nanoneedle field electron emitters; the combination results in a 20 mW output and a 4% power efficiency. The handheld emitter is driven by ordinary AA batteries. The graphene needles have tip radii <5 nm, boosting their electron-emitting efficiency, and operate in a small evacuated glass tube capped by the quantum well on a substrate. Electron-emitter lifetime testing shows >10,000 hours so far. Improving the light-extraction efficiency could boost power efficiency from 4% to 25%, say the researchers.
Source:
