A Japanese research group succeeded in making a deep ultraviolet LED that has the world's highest levels of output characteristics.
The group includes Akinori Koukitu and Yoshinao Kumagai, who are professor and associate professor, respectively, at the Division of Applied Chemistry, the Tokyo University of Agriculture and Technology (TUAT), and researchers of Tokuyama Corp.
With a forward current of 150mA, its output and external quantum efficiency are 20mW and 3.0%, respectively. Tokuyama will start to let users evaluate the LED within 2013, aiming to commercialize it by fiscal 2015. The company expects that the LED will replace disinfectant mercury lamps used in the fields of medical care, water purification and food manufacturing.
There were two problems in the development of the deep ultraviolet LED: developing a high-quality single-crystal substrate made of aluminum nitride (AlN), which is the main material, and making a deep ultraviolet LED structure. To solve those problems, a research team was formed by researchers of TUAT, Tokuyama, North Carolina State University and HexaTech Inc.
TUAT established a method to rapidly grow high-purity AlN crystal with its own hydride vapor phase epitaxy (HVPE) technology and obtained a basic patent for it in Japan and the US in cooperation with TUAT-TLO Co Ltd. North Carolina State University and HexaTech developed a technology to form seed crystal with a sublimation technique that enables to grow AlN with a low defect density though deep ultraviolet rays do not pass through it.
This time, the research group realized an AlN substrate that has both a high deep ultraviolet ray transmission rate and a low defect density by using AlN that was rapidly grown with the HVPE technology on AlN seed crystal made with a sublimation technique for the first time in the world. Tokuyama obtained a license to use the HVPE technology, established a volume production technique with it, formed 260nm-band (UV-C) ultraviolet LEDs optimal for use in sterilization on the substrate and confirmed the world's highest levels of output characteristics.
The new deep ultraviolet LED features low environmental burden, long product life, small size, low power consumption, etc.