Seminars
Thu |
Status and Challenges of Ultraviolet-C LEDs based on Group-III NitridesDr. Andrew A. Allerman, Sandia National Laboratories, Albuquerque, NM | |
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Abstract: Many applications currently serviced by Hg lamps would benefit from the availability of efficient solid-state emitters with emission at ultraviolet wavelengths (400-200 nm). UV-C wavelengths (280 – 200 nm) are effective at disrupting the DNA of viruses and bacteria and are utilized in germicidal applications ranging from water purification, medical instrument sterilization and air purification in building HVAC systems. These wavelengths are also effective for biological agent detection as signature proteins fluoresce with characteristic spectra under UV illumination. While Hg lamps are a mature and relatively efficient technology, they exhibit short lifetimes and transients during start-up and present hazarads if broken. Consequently, UV light emitting diodes are an appealing technology for replacing Hg lamps. Alloys of AlGaN, a compound semiconductor material, are of interest since the bandgap can be tuned for emission from 365 nm (GaN) to 200 nm (AlN). To date, AlGaN-based LEDs exhibit low efficiencies (< 4 %) compared to other semiconductor-based LEDs with emission from blue to IR wavelengths. This presentation will introduce applications employing UV wavelengths followed by a review of the material and fabrication challenges limiting AlGaN-based LED performance. Finally, potential solutions to these challenges will be discussed. Biography: Dr. Andrew Allerman is a Principal Member of Technical Staff in the Advanced Materials Sciences Department at Sandia National Laboratories in Albuquerque, NM. He received a Ph.D in Physics (’92) from Auburn University. In 1993, he joined the Department of Electronic Materials Engineering at the Australian National University in Canberra, Australia as a Research Scientist. He returned to the US in 1994 and worked in the GaAs Facility at Texas Instruments in Dallas Texas. In 1995 he joined Sandia and developed MOCVD growth of Sb-based compound semiconductors for use in mid-infrared (3-5μm) laser diodes. He developed GaAs based Vertical Cavity Surface Emitting Lasers (VCSEL's) from 740nm to >1um and the growth of novel materials such as InGaAsN and GaAsSbN for long wavelength (1.3um) opto-electronics and high efficiency photovoltaic solar cells. In 2001 he started development of MOCVD growth of wide-bandgap nitride-based materials for electronic and optical devices, focusing on development of AlGaN-based LEDs and laser diodes. He has (co)authored over 200 publications and has 6 patents. Location: MIT Lincoln Laboratory |