Graphene-based Field-effect Transistor Structures for Terahertz Applications Ahmad Abbas *a , Mustafa Karabiyik a and Nezih Pala a a Florida International University, Department of Electrical and Computer Engineering, 10555 West Flagler Street, Miami, FL 33174 ABSTRACT We propose Terahertz (THz) plasmonic devices based on linearly integrated FETs (LFETs) on Graphene. LFET structures are advantageous for (THz) detection since the coupling between the THz radiation and the plasma wave is strongly enhanced over the single gate devices and accordingly higher-order plasma resonances become possible. AlGaN/GaN heterostructure LFETs with their high sheet carrier concentration and high electron mobility are promising for plasmonic THz detection. Nevertheless, our numerical studies show that room temperature resonant absorption of THz radiation by the plasmons in AlGaN/GaN LFETs is very weak even if the integration density is sufficiently large. Our simulations also demonstrate that similar LFETs on Graphene, which has very large electron mobility, can resonantly absorb THz radiation up to 5th harmonic at room temperature. Additionally, we investigated LFETs with integrated cavities on Graphene. Such Periodic Cavity LFETs substantially enhance the quality factor of the resonant modes. Keywords: Terahertz, THz, Graphene, Detector, Plasma, FET 1. INTRODUCTION Terahertz technologies utilize electromagnetic radiation in the frequency range between 300 GHz and 10 THz and their potential applications in biology, chemistry, medicine, astronomy and security are wide ranging. THz wavelengths have several properties that could promote their use as sensing and imaging tools. The envisioned prospect for THz applications fueled intense research in the last decade leading impressive advancements in emission and detection of THz radiation. Plasma wave propagation in two-dimensions (2D) has contributed to advancements in detection and control in THz spectral region 1 . Because of the nature of plasma wave propagation, device response that surpasses the electronic drift cutoff frequency limit was possible 1- 11 . Plasmonic THz detection devices with Si 2, 3 , III-V compounds 5-14 and GaN 13 based semiconductor structures were observed. These devices include single gate high electron mobility (HEMT) structures 7,9,10,11,13 , grating gate devices 5,6,12 and arrays of field effect transistors (FET) 14 . Single Gate devices were studied extensively for the detection of THz frequency 5,6,12 but the coupling efficiency to the THz wave is weak due to small power incident on the device. Accordingly, higher integration density of FETs with a cumulative effect led to the use of arrays. In all the previous THz plasmonic detectors, very weak or no response in room temperature due to higher electron scattering rates was observed. Lately the high mobility properties of Graphene in room temperature was utilized in a THz detector as a 2D channel 15 but the THz absorption modes had very low quality factors. Plasma waves in FET structures are governed by two different dispersion relations (i.e. gated and ungated plasmons). If an infinite perfectly conductive plane is located at distance d from the infinite 2D electron, then the dispersion relation for the gated plasmons is given by (equation 1) below 24 * ahmad.nabil.abbas@gmail.com Terahertz Physics, Devices, and Systems VI: Advanced Applications in Industry and Defense, edited by A. F. Mehdi Anwar, Nibir K. Dhar, Thomas W. Crowe, Proc. of SPIE Vol. 8363, 83630S © 2012 SPIE · CCC code: 0277-786X/12/$18 · doi: 10.1117/12.919460 Proc. of SPIE Vol. 8363 83630S-1 Downloaded from SPIE Digital Library on 19 Jun 2012 to 139.179.10.194. Terms of Use: http://spiedl.org/terms