Los Alamos Women in Science
Northern Chapter of the New Mexico Network for Women in Science and Engineering

co-sponsored by
Synergy Center,  UNM-LA, and  LANL CPO
Talk at 12:00 noon, Tuesday, 17 July 2007
Bldg 1, Los Alamos Research Park
Synergy Center Conf. Rm, 3rd flr


Mid-IR Type-II InAs/GaSb Nanoscale Superlattice Sensors
Elena Plis, University of New Mexico
The detection of mid-wavelength infrared radiation (MWIR) is very important for many military, industrial and biomedical applications. Present-day commercially available uncooled IR sensors operating in MWIR region (2-5 µm) use microbolometric detectors which are inherently slow. Available photon detectors (mercury cadmium telluride (MCT), bulk InSb and quantum well infrared detectors (QWIPs)) overcome this limitation. However, there are some fundamental issues decreasing their performance and ability for high temperature operation, including fast Auger recombination rates and high thermal generation rate. These detectors operate at low temperatures (77K-200K) in order to obtain high signal to noise ratio. The requirement of cooling limits the lifetime, increases the weight and the total cost, as well as the power budget, of the whole infrared system. In recent years, InAs/GaSb superlattice based detectors have appeared as an interesting alternative to the present-day IR detector systems.

These heterostructures have a type-II band alignment such that the conduction band of the InAs layer is lower than the valence band of the GaSb layer. The effective bandgap of these structures can be adjusted from 0.4 eV to values below 0.1 eV by varying the thickness of constituent layers leading to an enormous range of detector cutoff wavelengths (3-30 µm). The InAs/GaSb superlattices have a higher degree of uniformity than the MCT alloys, making them attractive for large area focal plane arrays. They provide a smaller leakage current due to larger effective electron mass, which suppresses tunneling. This material system is also characterized by high operating temperatures and long Auger recombination rates. This suggests the potential for using the superlattice technology for realizing high operating temperature devices.

The thesis research summarized in this talk focused on the development of mid-IR InAs/GaSb superlattice sensors with high-operating temperature. Contributions from this research include 1) development of growth and processing procedure for the n-on-p and p-on-n design of superlattice detectors leading to improved detector performance, 2) careful evaluation of characteristics of superlattice detectors, and 3) methods of reduction of surface component of dark current (passivation techniques).

Biography - Elena Plis received her Engineering degree from the Kovrov State Technological Academy, Russia in 2001. She completed her MS in Electrical engineering from the University of New Mexico, USA in 2005. Currently, she is a PhD student of Electrical and Computer Engineering Department at the Center for High Technology Materials, University of New Mexico. Her present research interests include growth, fabrication and characterization type II InAs/InGaSb based strain layer superlattices for mid infrared lasers and detectors. Elena has authored/co-authored 8 peer-reviewed journal articles and conference presentations. She has been IEEE Student Member since 2003 and SPIE Student Member since 2006.
 KRSN Interview: broadcast Monday, 16 July 2007, at about 8:40 am, after the sports on KRSN's live morning show. See http://www.krsnam1490.com/ for KRSN live stream.

If you would like to arrange to speak with Elena during her visit, please contact Tinka Gammel, jtg@lanl.gov, 667-9149.
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