Ultra Violet Lamps based on the Electron-Pumping of III-nitrides nanostructures using Carbon Nanotube Cathodes – UVLamp

A new generation of electron pumped ultraviolet (UV) lamps will be developed where light is emitted from III-nitride semiconductor nanostructures that are excited by carbon nanotube (CNT) field emission (FE) cathodes.
UV sources are used for many industrial, medical and analytical applications such as adhesive curing, covert communication, biodetection, phototherapy and water purification. The UV market, about 500 million US$ in 2009, is currently covered by mercury vapor lamps which are cheap but feature many inconveniences such as limited lifetime, power stability and portability. Most importantly mercury is toxic to humans and the environment, and the phasing out of medical devices containing mercury is already underway in many countries. UV lamps based on light emitting III-nitride nanostructures are environmentally-friendly and mercury-free.
This electron pumped UV lamp will go well beyond the state of the art in energy consumption, emission power, cost, brightness and recyclability by making use of three technological advances :
1. For the first time emission in deep UV cab be obtained from quantum dots (QDs) and nanodisks (NDs) embedded in photonic nanowires (NWs). Using these nanostructures in the active region should allow more efficient conversion of injected carriers into photon emission.
2. This first use of photonic NWs in the active region should boost the light extraction efficiency through wave guiding (up to 50%).
3. Compact CNT FE cathodes emit much higher current densities than other sources.
Two fully operational prototypes will be developed, one emitting at 260 nm for water purification and another emitting at 310 nm for treatment of psoriasis with UV power in excess of 150 mW. The compact demonstrators will also serve for the next manufacturing phase and market exploration.
The consortium consists of four complementary partners that have the required competences and infrastructures in all the necessary domains:
P1. LPMCN-UCBL/CNRS (abv. UCBL): Coordination, CNT FE electron sources
P2. INAC/SP2M-CEA (INAC): Synthesis of AlGaN QDs
P3. Institut Néel-CNRS (NEEL): Synthesis of AlGaN NDs in photonic NWs.
P4. NEWSTEP Tech. SAS (NSTP): Lamp design, fabrication, manufacture costs, marketing.
The pairs UCBL-NSTP and INAC-NEEL are already collaborating with corresponding agreements on Intellectual Properties. UCBL has been working with NSTP to develop new forms of home lighting using cathodoluminescence excited by CNT FE sources. The experience and infrastructure are directly applicable to our UVLamp. INAC and NEEL are part of the mixed CEA-CNRS “Nanophysique et Semiconducteurs” lab which has extensive facilities for the growth of advanced semiconductors by Molecular Beam Epitaxy (MBE). Le Si Dang (NEEL) will oversee the development of semiconductor nanostructures. His expertise has been recognized by his receiving the coveted Gentner-Kastler prize. S.Purcell(UCBL) has published the definitive article on FE from CNTs that describes the mechanisms controlling maximum FE currents. G.Tocu (NSTP) has a wide experience in vacuum electron devices and running industrial projects.
The technological challenges include:
• Growth of QDs and NDs in photonic NWs emitting over the whole 210-350 nm range to form the active region with internal quantum efficiency > 50%.
• Increasing FE currents above the present 1-3 mA while obtaining sufficient lifetimes, i.e. >1000hr to start and eventually 3000 hours.
• Integrating the semiconductor nanostructures and CNT cathodes without degradation into a quartz vacuum envelope.
Perspectives:
Solid state UV lighting is a young technology that is opening many new industrial opportunities. The present performance levels of our components could already lead to a highly competitive product. Combining the projected performance improvements with compact sources for flexible design will permit scaling up to higher power levels, thus addressing more varied and larger scale applications.