AbstractTHz Detection and Imaging using Graphene Ballistic Rectifiers

Gregory Hunter Auton, Dmytro But, jiawei Zhang, Ernie W. Hill, Dominique Coquillat, Christophe Consejo, Philippe Nouvel, Wojciech Knap, Luca Varani, Frederic Teppe, Jeremie Torres, and Aimin Song

http://pubs.acs.org/doi/abs/10.1021/acs.nanolett.7b03625?journalCode=nalefd

A graphene ballistic rectifier is used in conjunction with an antenna to demonstrate a rectenna as a terahertz (THz) detector. A small-area (<1 μm2) local gate is used to adjust the Fermi level in the device to optimise the output while minimising the impact on the cut-off frequency. The device operates in both n- and p-type transport regimes and shows a peak extrinsic responsivity of 764 V/W and a corresponding noise equivalent power of 34 pW Hz-1/2 at room temperature with no indications of a cut-off frequency up to 0.45 THz. The device also demonstrates a linear response for more than three orders of magnitude of input power due to its zero threshold voltage, quadratic current-voltage characteristics and high saturation current. Finally, the device is used to take an image of an optically opaque object at 0.685 THz, demonstrating potential in both medical and security imaging applications.

Abstract-Terahertz imaging of Landau levels in HgTe-based topological insulators

Aleksandr M. Kadykov1,2, Jeremie Torres3, Sergey S. Krishtopenko1,2,Christophe Consejo1, Sandra Ruffenach1, Michal Marcinkiewicz1, Dmytro But1, Wojciech Knap1,4, Sergey V. Morozov2,5, Vladimir I. Gavrilenko2,5,Nikolai N. Mikhailov6,7, Sergey A. Dvoretsky6 and Frederic Teppe1,a)

1 Laboratoire Charles Coulomb (L2C), UMR 5221 CNRS–Université de Montpellier, Montpellier, France

2 Institute for Physics of Microstructures, Russian Academy of Sciences, GSP-105, 603950 Nizhny Novgorod, Russia

3 Institut d'Electronique et des Systèmes (IES), UMR 5214 CNRS–Université de Montpellier, Montpellier, France

4 Institute of High Pressure Institute Physics, Polish Academy of Sciences, 01-447 Warsaw, Poland

5 Lobachevsky State University of Nizhny Novgorod, 603950 Nizhny Novgorod, Russia

6 Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, pr. Akademika Lavrent'eva 13, 630090 Novosibirsk, Russia

7 Novosibirsk State University, 630090 Novosibirsk, Russia

a) Electronic mail: frederic.teppe@umontpellier.fr

http://scitation.aip.org/content/aip/journal/apl/108/26/10.1063/1.4955018

Appl. Phys. Lett. 108, 262102 (2016); http://dx.doi.org/10.1063/1.4955018

We report on sub-terahertz photoconductivity under the magnetic field of a two dimensional topologicalinsulator based on HgTe quantum wells. We perform a detailed visualization of Landau levels by means of photoconductivity measured at different gate voltages. This technique allows one to determine a criticalmagnetic field, corresponding to topological phase transition from inverted to normal band structure, even in almost gapless samples. The comparison with realistic calculations of Landau levels reveals a smaller role of bulk inversion asymmetry in HgTe quantum wells than it was assumed previously.

Abstract-Heterostructured hBN-BP-hBN Nanodetectors at Terahertz Frequencies

http://onlinelibrary.wiley.com/doi/10.1002/adma.201601736/abstract

By reassembling the thin isolated atomic planes of hexagonal borum nitride (hBN) with a few layer phosphorene (black phosphorus BP), hBN/BP/hBN heterostructures were mechanically stacked to devise high efficiency THz photodetectors operating in the 0.3–0.65 THz range, from 4K to 300K, with a record signal-to-noise ratio of 20000.