Abstract-Limiting factors for optical switching using nano-structured graphene-based field effect transistors

Ramin Emadi, Zaker Hossein Firouzeh, Reza Safian,  Abolghasem Zeidaabadi Nezhad

https://www.osapublishing.org/ao/abstract.cfm?uri=ao-58-3-571

Thanks to the particular band diagram of graphene, it is recognized as a promising material for developing optoelectronic devices at the nano-scale. In this paper, a functional stack comprised of graphene and other materials is numerically investigated to extract the related capacitance-voltage curve by taking into account practical considerations regarding the nano-structured electronic devices. Polycrystalline silicon gates are used as electrical contacts in this stack, which are considered as semiconductor materials rather than metal contacts owing to the nano-scale dimensions of the constitutive materials. Moreover, graphene is effectively modeled to highlight its presence in the stack. Then, the stack is developed for the construction of a graphene field effect transistor (GFET) in order to examine the speed response of the stack. In this regard, by selecting the carrier mobility of 1500  cm2/(V·s)$\mathrm{}{}^{\mathrm{}}\mathrm{}\mathrm{}$ for graphene and a particular bias condition, the small-signal current gain of the GFET is computed so that according to the simulation results, the intrinsic cutoff frequency of 13.89 GHz is achieved.

© 2019 Optical Society of America

Abstract-THz plasma wave instability in field effect transistor with electron diffusion current density

Hongmei Du, Liping Zhang,  Dongao Li,

http://iopscience.iop.org/article/10.1088/2058-6272/aacaef/pdf


The instability of plasma waves in rectangle Field Effect Transistors (FETs) is studied with electron diffusion current density by quantum hydrodynamic model in this paper. General dispersion relation including effect of quantum effects, external friction associated with electron scattering, electron exchange-correlation contributions and thermal motion of electrons were obtained for rectangle FETs. The electron diffusion current density term is considered for further analysis in this paper. It is found that the quantum effects, the electron diffusion current density and the thermal motion of electrons enhance the radiation power and frequencies. But the electron exchange-correlation contributions and the external friction associated with electron scattering reduce the radiation power and frequencies. Results showed that a transistor has advantages for the realization of practical terahertz sources.

Abstract-Field effect transistors for terahertz applications

W. Knap, M.I. Dyakonov,

https://www.sciencedirect.com/science/article/pii/B9780857092359500057

This chapter gives an overview of the main physical ideas and experimental results concerning the application of field effect transistors (FETs) for the generation and detection of terahertz (THz) radiation. Resonant frequencies of the two-dimensional plasma oscillations in FETs increase with the reduction of the channel dimensions and for submicron gate length reach the THz range. When the mobility is high enough, the dynamics of a short channel FET at THz frequencies is dominated by plasma waves. This may result, on the one hand, in a direct current (dc) induced spontaneous generation of plasma waves and THZ emission and, on the other hand, in a resonant photoresponse to incoming radiation. In other cases, when plasma oscillations are overdamped, the FET can operate as an efficient broadband THz detector.

Abstract-Handbook of Terahertz Technology for Imaging, Sensing and Communications

W. Knap, M.I. Dyakonov,

https://www.sciencedirect.com/science/article/pii/B9780857092359500057

This chapter gives an overview of the main physical ideas and experimental results concerning the application of field effect transistors (FETs) for the generation and detection of terahertz (THz) radiation. Resonant frequencies of the two-dimensional plasma oscillations in FETs increase with the reduction of the channel dimensions and for submicron gate length reach the THz range. When the mobility is high enough, the dynamics of a short channel FET at THz frequencies is dominated by plasma waves. This may result, on the one hand, in a direct current (dc) induced spontaneous generation of plasma waves and THZ emission and, on the other hand, in a resonant photoresponse to incoming radiation. In other cases, when plasma oscillations are overdamped, the FET can operate as an efficient broadband THz detector.

Abstract-Modeling of Field Effect Transistor Channel as a Nonlinear Transmission Line for Terahertz Detection

• Nihal Y. Ibrahim, 
• Nadia H. Rafat, 
• Salah E. A. Elnahwy

http://link.springer.com/article/10.1007%2Fs10762-013-0009-0

This paper revisits the theory of operation of field effect transistor in the extremely high frequency scale, where the analysis has gone beyond the conventional cutoff frequency of the transistor. In this range, which is typically the terahertz (THz) and sub-terahertz range, the transistor blocks the high frequency signal and generates a rectified signal related to the input high frequency signal. An analytical model is derived for the channel of the FET in the linear mode of operation in non-resonant THz detection conditions. A transmission line distributed circuit model is applied. This is, from the authors’ point of view, the suitable model for high frequency non-quasi static operation and the characteristic parameters of this model are derived from the differential equation governing the electron gas in the channel. A comparison is presented for the calculated photoresponse with previously published experimental one showing good agreement away from the threshold potential. Finally, the effects of coupling between the present model and the external input circuit have been taken into account including the loading effects of the antenna and a discussion is given for the effect on frequency selectivity of the FET.