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Sheraton Frankfurt Airport Hotel 04 March


High Efficiency Germicidal UV LEDs


Through a DARPA program (CMUVT): Compact Mid Ultraviolet Technology and with assistance from Army Research Labs Sensor Electronic Technology Inc. (SETi) has performed a research program that has led to dramatic improvements in performance of UV LEDs operating in the germicidal wavelength range. SETi is the world leader in the development and commercialization of Deep UV LEDs (LEDs shorter than 365nm). SETi’s product portfolio covers the entire wavelength range from 240nm to 365nm and includes LED’s, LED lamps, LED light sources and fully integrated custom solutions. SET’s, Deep UV LEDs were first introduced into the market in 2004 following an earlier DARPA development and for which SETi was recognised by DARPA in their 50 year anniversary Success Stories. Over the past 8 years SETi has made many technological improvements to its LEDs but has focused much of its attention to improving reproducibility and reliability for customers in highly demanding markets including scientific instrumentation, life sciences, military and space exploration. In this time SETi has obtained conformance with ISO9001 AS9100 and has been space flight qualified.


Over the years the efficiency of these devices has seen some modest improvements and commercially available LEDs operate at 1-2% wall-plug efficiency (WPE). However the result of this current R&D effort has to date seen an increase in WPE to over 8%.


What industry challenge does this address? Based in the AlGaN materials system Deep UV LEDs often suffer from extremely low WPE due to high dislocation densities in the epi low internal quantum efficiency (IQE) low injection efficiency and poor extraction efficiency. SETi has previously solved these issues to a point where Deep UV LEDs can be commercialised however this new R&D program takes Deep UV LED performance to a new level.


How does it solve the problem?


Improvements of the internal quantum efficiency by reduction of the threading dislocation density and of the light extraction by using UV transparent p-type contact layer UV reflecting ohmic contact and chip encapsulation with optimised shape and refractive index allowed us to obtain the external quantum efficiency of 10.4% at 20mA CW current with the output power up to 9.3 mW at 278nm for AlGaN based deep ultraviolet light- emitting diodes grown on sapphire substrates.


CS Industry Awards winners will be announced on 4th


March at the Sheraton Frankfurt Airport Hotel, Germany at the CS International Conference. www.cs-international.net


54 www.compoundsemiconductor.net January / February 2013


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