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Design and Fabrication of Fractal Photoconductive Terahertz Emitters and Antenna Coupled Tunnel Diode Terahertz Detectors Open Access


Other title
Terahertz detectors
Atomic Layer Deposition
photoconductive switch
THz Pump-probe
Terahertz Spectroscopy
Electron Tunnel Diode
Antenna Coupled MIM detectors
Terahertz Radiation
Terahertz Imaging
Terahertz antenna
Time Resolved
Type of item
Degree grantor
University of Alberta
Author or creator
Maraghechi, Pouya
Supervisor and department
Elezzabi, Abdulhakem (Electrical and Computer Engineering)
Examining committee member and department
Cadien, Ken (Chemical and Materails Engineering)
Tsui, Ying (Electrical and Computer Engineering)
Beigang, Rene (University of Kaiserslautern, Germany)
Nowrouzian, Behrouz (Electrical and Computer Engineering)
Barlage, Doug (Electrical and Computer Engineering)
Elezzabi, Abdulhakem(Electrical and Computer Engineering)
Miller, James (Electrical and Computer Engineering)
Jacob, Zubin (Electrical and Computer Engineering)
Department of Electrical and Computer Engineering
Date accepted
Graduation date
Doctor of Philosophy
Degree level
Improved terahertz (THz) photoconductive antennas that are able to both emit higher THz radiation power and detect lower THz radiation signal levels than the traditional THz photoconductive antennas are presented. Also, different classes of fractals are investigated to realize whether the enhanced THz radiation properties of fractal photoconductive THz emitters are universal to all fractals. Finally, the effect of self-similarity of the antenna structure on its performance is studied. New classes of metal-insulator-metal (MIM) junctions that possess extreme asymmetry and nonlinearity in their current-voltage (I-V) characteristics are investigated. Metal-insulator-insulator-metal (MIIM) diodes incorporating different electron tunneling mechanisms under forward and reverse bias are implemented through the introduction of a cascaded potential barrier. A high I-V nonlinearity, up to 10 times that of a conventional MIM, was obtained for identical metal electrodes. As the next step, the tunneling mechanism is further altered. For this, resonant tunneling transport is incorporated into a metal-insulator-insulator-insulator-metal (MIIIM) diode. This is analogous to a tunnel diode (normal tunneling) with the mechanism of a resonant tunneling device. It is envisioned that high speed THz rectifiers, ultrahigh bandwidth frequency mixers, diodes, and electron tunnel transistors having extraordinary I-V nonlinearity can be realized. Next, the tunnel diodes are integrated into the antenna-coupled detectors for detecting free space THz radiation. The fabrication process for the MIIM, and MIIM diodes having an integrated antenna has been presented. To accomplish this, the knowledge gained from designing and fabricating optimized THz fractal antennas and highly nonlinear MIIM and MIIIM diodes is utilized for fabricating ultrafast THz detectors. Finally, the capabilities of THz spectroscopy for characterizing and studying the time dynamics of devices and complicated systems were investigated. To accomplish these tasks, a versatile optical setup for all-THz time resolved pump-probe spectroscopy was designed and tested. This THz setup is used to potentially characterize the temporal and spectral response of the fabricated antenna coupled MIIM and MIIIM diodes. Importantly, utilizing this setup and conventional THz time-domain spectroscopy (THz-TDS), the interaction of THz waves with complex media such as metal-dielectric composites was investigated. This was to expand the utilization of THz imaging from imaging inside dielectric materials into imaging more complex materials largely composed of highly opaque substances. The knowledge gained through a series of experiments was applied in utilizing THz-TDS for imaging dielectric objects embedded inside metallic media. This advancement of THz-TDS was successfully accomplished.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Pouya Maraghechi, A. Foroughi-Abari, K. Cadien, and A.Y. Elezzabi, “Observation of resonant tunneling phenomenon in metal-insulator-insulator-insulator-metal electron tunnel devices”, Applied Physics Letters, 100, 113503, 2012.A. Y. Elezzabi and Pouya Maraghechi, “A versatile and reconfigurable setup for all-terahertz time-resolved pump-probe spectroscopy”, Review of Scientific Instruments, 83, 053107, 2012.Pouya Maraghechi, A. Foroughi-Abari, K. Cadien, and A.Y. Elezzabi, “Enhanced rectifying response from metal-insulator-insulator-metal (MIIM) junctions”, Applied Physics Letters, 99, 253503, 2011.Pouya Maraghechi and A.Y. Elezzabi, “The role of self-similarity in fractal photoconductive THz emitters”, Journal of Infrared, Millimeter, and Terahertz Waves, 32, 11, 1285-1290, 2011.Pouya Maraghechi, K. Cadien and A.Y. Elezzabi, “A Novel Nanofabrication Damascene Lift-Off Technique”, IEEE Trans. on Nanotechnology, 10, 4, 822-6, 2011.Pouya Maraghechi and A. Y. Elezzabi, “Experimental confirmation of design techniques for effective bow-tie antenna lengths at THz frequencies”, Journal of Infrared, Millimeter, and Terahertz Waves, 32, 7, 897-901, 2011.Pouya Maraghechi and A. Y. Elezzabi, “Enhanced THz Emission from Plasmonic Complementary Sierpinski Fractal Emitters”, Optics Express, 18, No. 26, 27336-45, 2010.Pouya Maraghechi, C. Straatsma et al. “Plasmon-assisted terahertz imaging inside metal-filled media”, , Optics Express, 17, No. 19, 16456-64 2009.A.Y. Elezzabi, K.J. Chau, C. Baron and Pouya Maraghechi, “A Plasmonic Random Composite with Atypical Refractive Index”, Optics Express, 17, No. 2, 1016-22, 2009.

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