Title: Terahertz Plasma Excitations in Field Effect Transistors: Physics and First Applications for Imaging

Speaker:  Prof. Wojciech Knap(University of Montpellier 2 & CNRS，France)

Time: Sep4 2009 14:00(PM)

Venue：Institute of Semiconductors,  CAS

　  Abstract：Resonant frequencies of the two-dimensional plasma in FETs increase with the reduction of the channel dimensions and can reach the THz range for nanometer channel lengths 1,2. Nonlinear properties of the electron gas in the transistor channel can be used for the detection of THz radiation. The possibility of tuneable narrow band detection in sub-THz and THz range, related to plasma resonances, has been demonstrated for short gate transistors at cryogenic temperatures3.At room temperatures - the plasma oscillations are usually strongly damped damped, but  FETs can still operate as an efficient broadband detector in the THz range . We discuss the results obtained on different FETs – comparing III-V GaAs3,4,6 and GaN HEMTs with Si- MOSFETs 5. We present the main theoretical and experimental results on THz detection by FETs in the context of their possible application for THz imaging7.

　  About Prof. Wojciech Knap：He was born in Zakopane, Poland, in 1955. He graduated from the University of Warsaw in 1979, received PhD in 1985. From 1987 he worked in different research and education institutions in France –University Montpellier2 Grenoble and Toulouse  High Magnetic Laboratories. In 1992 he got a permanent position as a researcher  in CNRS Montpellier. He was also visiting professor/researcher at Rensselaer Polytechnic Institute, Troy, New York, USA, 1999/2001 and Tohoku University – Sendai Japan 2007/2008. Currently, he is Director of Research in the CNRS-GES Montpellier and is also coordinator of the European  Research Network (E-GDR) “Semiconductor Sources and Detectors of Terahertz Radiation”. His research involves solid state physics and Far-IR (Terahertz) optics in semiconductor nanostructures.