ISDRS 2007, December 12-14, 2007, College Park, MD, USA ISDRS 2007 – http://www.ece.umd.edu/ISDRS Plasma wave FET for sub-wavelength THz imaging D. B. Veksler a , A. V. Muraviev a,b , T. A. Elkhatib a , K. N. Salama a , and M. S. Shur a a ECSE, Physics, and CIE, Rensselaer Polytechnic Institute, USA,veksld@rpi.edu, b Institute for Physics of Microstructures RAS, Russian Federation. Many terahertz (THz) applications, such as medical imaging, require higher resolution than the diffraction limit, and they rely on sub-wavelength imaging techniques. Such techniques employ sharp needles to concentrate the THz field near the tip [1,2], subwavelength diaphragms [3], or optically induced diaphragms [4]. In this paper we show, that micrometer scale and even nanometer scale resolution imaging can be achieved with the field effect transistor operating in a plasma wave detector mode [5-9] by changing drain and gate biases. This paper reports on the first ever THz imaging employing plasma wave field-effect transistors (FETs), unlike references [5-9] reporting on THz sensing. Field-effect transistors with nano-scale gates detect terahertz radiation at frequencies far above their cutoff frequencie via excitation of resonant or damped plasma waves (which are waves of electron density in 2D electron gas under the gate or in the ungated region) [5-9]. In this paper, we recorded the image of the transistor responsivity pattern as a dependence of the drain- to- source voltage, induced by the THz laser radiation versus the displacement of the transistor in perpendicular plane in respect to the laser beam. In our experiments, we used commercial high electron mobility transistors (HEMTs) from Fujitsu [10] with gate length of 250 nm and width of Fig. 1. a) Experimental setup for sub-wavelength terahertz imaging of plasma-wave transistor, b) Optical image of the transistor is shown in the same scale for comparison, c,d) THz images of AlGaAs/GaAs HEMT recorded as the dependence of the transistor response vs. its displacement with 5m step at different biasing conditions 0 100 200 300 400 500 0 100 200 300 400 500 I d =5 mA, V gs = -0.3 V Response (a.u.) X (m) Y (m) -1E0 -5E-1 0 5E-1 1E0 0 100 200 300 400 500 0 100 200 300 400 500 I d =5 mA, V gs = -0.4 V Response (a. u.) X (m) -1E0 -5E-1 0 5E-1 1E0 Source Drain Gate (a) (b) (c) (d) 978-1-4244-1892-3/07/$25.00 ©2007 IEEE