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Proceedings Paper

Can geometric diodes improve performance of optical rectennas?
Author(s): John Stearns; Garret Moddel
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Paper Abstract

Infrared rectennas often use metal-insulator-insulator-metal (MIIM) diodes since their femtosecond scale tunneling is fast enough to rectify terahertz signals. Many factors threaten to degrade the rectenna performance, such as impedance matching with the antenna and material losses at frequency, but the most challenging limitation is the diode’s rectification efficiency. Geometric diodes, planar conductors with a geometric asymmetry that imposes a preferred current direction, offer several advantages over MIIM diodes including negligible capacitance and greater tolerance to high input powers. For carriers to experience the geometric features that promote current asymmetry, their mean-free-path length must be on the order of, or greater than, critical device dimensions. Graphene, with long carrier mean-free-path lengths, is therefore a choice material. By optimizing the geometry of these diodes, their current-voltage characteristics can be made to exhibit large current asymmetries, which is crucial for efficient rectification. The challenge is tuning the geometry to achieve large asymmetries at sufficiently low voltages for efficient operation in rectennas. A Monte Carlo simulator tracked the motion of electrons under an applied bias to determine the current-voltage characteristics for geometric diodes of a specified shape, and various geometries were analyzed to deduce important diode parameters. The current-voltage characteristics were then used in a rectifier circuit simulator to assess attainable rectification efficiencies, and compare them to those of the best projected MIIM diode from a quantum tunneling simulator. The results suggest that geometric diodes may offer improved rectification efficiencies over MIIM diodes for high input powers.

Paper Details

Date Published: 3 September 2019
PDF: 7 pages
Proc. SPIE 11089, Nanoengineering: Fabrication, Properties, Optics, Thin Films, and Devices XVI, 1108903 (3 September 2019); doi: 10.1117/12.2527701
Show Author Affiliations
John Stearns, Univ. of Colorado, Boulder (United States)
Garret Moddel, Univ. of Colorado, Boulder (United States)

Published in SPIE Proceedings Vol. 11089:
Nanoengineering: Fabrication, Properties, Optics, Thin Films, and Devices XVI
Balaji Panchapakesan; André-Jean Attias, Editor(s)

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