This Small Business Innovation Research (SBIR) Phase I project will result in developing novel high-power, high-efficiency Deep Ultraviolet Light Emitting Diode (DUV LED) Lamps based on an innovative and new micro-pixel device design. Deep ultraviolet light sources with emission wavelengths lambda from 250 - 365 nm are used in many applications including water/air purification, analytical scientific instrumentation, bio-agent detection systems and emerging miniaturized bio-medical instrumentation. Aluminum-indium-gallium-nitride (AlInGaN) based DUVLEDs have recently been developed and commercialized. However at present their external quantum efficiency and output powers are only 1-2% and 1-2 mW in continuous operating mode. One of the primary causes of these low numbers is current crowding arising from the resistance of the n-AlGaN buffer layers. To address this challenge large area LEDs with micro-pixel device geometry with expected output powers of 15-20mW and a stable operation with lifetime over 3000 hours are being developed. New approaches are being developed for the n-AlGaN buffer layers and the active layers deposition to increase their thickness, avoid cracking, and reduce their resistance and defects.
The broader impact/commercial potential of this project represents a new opportunity for developing semiconductor materials based solid-state deep ultraviolet light sources. The targeted performance will allow for penetration into large existing UV market segments such as water purification, medical instrumentation and UV polymer curing. The deep ultraviolet optoelectronic field continues to grow each year and the expertise gained through this program will contribute to the advancement of novel DUV light sources. The project will also lead to jobs for graduates from local Universities and Technical Institutes thereby fostering high-tech economic development in the state of South Carolina. Moreover the project will significantly enhance the knowledge base in high-aluminum content AlInGaN materials science, their epitaxial deposition and processing and packaging. There is a very high probability of transitioning the knowledge base and the developed technology to commercial products for disinfection/purification and polymer curing markets.
This Small Business Innovation Research (SBIR) Phase I project resulted in developing ultraviolet light emitting diode based on a novel micro-pixel device design. Deep ultraviolet light sources with emission wavelengths from 250 - 365 nm are used in many applications including water/air purification, analytical scientific instrumentation, bio-agent detection systems and emerging miniaturized bio-medical instrumentation. DUV light emitting diodes (DUVLEDs) with powers over 10mW and life time over few thousand hours can replace the existing DUV technology. Aluminum-indium-gallium-nitride (AlInGaN) based DUVLEDs have recently been developed and commercialized. However at present their external quantum efficiency and output powers are only 2-4% and 1-3 mW in continuous operating mode. One of the primary causes of these low numbers is current crowding arising from the resistance of the n-AlGaN buffer layers. During Phase I period, we have succeeded in depositing high quality (dislocation density < 108 cm-2), crack free, thick (> 2 micron) AlN on sapphire substrates and AlGaN layers with dislocation density less than 109 cm-2 and thickness of more than 4 micron on high quality AlN buffers. In addition, we have fabricated 280nm UVLEDs over these low dislocation density templates with a novel micropixel design. Improvement in device packaging includes heat sink for better thermal management and UV transparent epoxy encapsulation has lead to highly efficient UVLEDs with output powers over 2mW at 20mA. The milestones achieved during phase I of this program are very promising and clearly establish the feasibility of producing the commercially viable DUVLED and lamps. The broader impact/commercial potential represents a new opportunity for developing semiconductor materials based solid-state deep ultraviolet light sources. The results achieved from this project are promising and will allow for penetration into large existing UV market segments such as water purification, medical instrumentation and UV polymer curing. The project has helped us to collaborate and hire graduates from Midlands Technical College, Columbia and ITT technical Institute, Columbia fostering high-tech economic development in the state of South Carolina. Moreover the project has led significantly to enhance the scientific knowledge base in epitaxy of III-nitrides, their processing and packaging. There is a very high probability of transition of this high technology for commercialization of UV products for disinfection/purification and polymer curing markets.
