Abstract-Negative and positive terahertz and infrared photoconductivity in uncooled graphene

Victor Ryzhii, Dmitry S. Ponomarev, Maxim Ryzhii, Vladimir Mitin, Michael S. Shur, and Taiichi Otsuji

Fig. 1 Upper panel: the normalized carrier temperature variation (T − T0)/T0 (dashed lines) for different values of the parameter b (upper panel) and τ0 = 1 ps and the quasi-Fermi energy μ/T (solid line) for b = 0.1 and τ0 = 1 ps. Lower panel: the normalized carrier temperature variation (T − T0)/T0 (dashed line) for b = 0.1 and τ0 = 1 ps and the quasi-Fermi energy μ/T (solid lines) for b = 1 and different τ0.

https://www.osapublishing.org/ome/abstract.cfm?uri=ome-9-2-585

We develop the model for the terahertz (THz) and infrared (IR) photoconductivity of graphene layers (GLs) at room temperature. The model accounts for the linear GL energy spectrum and the features of the energy relaxation and generation-recombination mechanisms inherent at room temperature, namely, the optical phonon absorption and emission and the Auger interband processes. Using the developed model, we calculate the spectral dependences of the THz and IR photoconductivity of the GLs. We show that the GL photoconductivity can change sign depending on the photon frequency, the GL doping and the dominant mechanism of the carrier momentum relaxation. We also evaluate the responsivity of the THz and IR photodetectors using the GL photoconductivity. The obtained results along with the relevant experimental data might reveal the microscopic processes in GLs, and the developed model could be used for the optimization of the GL-based photodetectors.

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Tunable Stub Plasmonic Structures for Terahertz Detectors and Sources

Michael S. Shur, Gregory R. Aizin, and J. Mikalopas

http://65.202.222.105/abstract.cfm?uri=FiO-2018-JW4A.75

Numerous applications of terahertz communication and sensing technology require powerful electronic sources and sensitive detectors. Recently proposed “plasmonic boom” terahertz devices require the electron velocity repeatedly cross the plasma velocity in periodic electronic structures. Such devices could increase the generated power and detection sensitivity by orders of magnitude. However, they require tuning boundary conditions at heterodimensional interfaces and decreasing the velocity of the plasmons. We propose using the protruding side regions attached to a plasmonic channel – “plasmonic stubs” – to control the boundary conditions and slow down plasmons in a controllable and tunable fashion. Using the transmission line modeling approach, we derive the expression for the input impedance of the device with a stub and show the input impedance could be tuned from minus to plus infinity. We derive and solve the dispersion equation for the plasmons and show the tunable plasma velocity decrease. These results are important for design, characterization, modeling, and parameter extraction of the next generation of THz electronic devices and circuits.

© 2018 The Author(s)

Abstract-Nonlinear response of infrared photodetectors based on van der Waals heterostructures with graphene layers

Victor Ryzhii, Maxim Ryzhii, Dmitry Svintsov, Vladimir Leiman, Vladimir Mitin, Michael S. Shur, and Taiichi Otsuji

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-5-5536&origin=search

We report on the device model for the infrared photodetectors based on the van der Waals (vdW) heterostructures with the radiation absorbing graphene layers (GLs). These devices rely on the electron interband photoexcitation from the valence band of the GLs to the continuum states in the conduction band of the inter-GL barrier layers. We calculate the photocurrent and the GL infrared photodetector (GLIP) responsivity at weak and strong intensities of the incident radiation and conclude that the GLIPs can surpass or compete with the existing infrared and terahertz photodetectors. The obtained results can be useful for the GLIP design and optimization.

© 2017 Optical Society of America