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| Pàgina inicial > Articles > Articles publicats > Does carrier velocity saturation help to enhance f in graphene field-effect transistors? |
(Universitat Autònoma de Barcelona) (Universitat Autònoma de Barcelona) (Chalmers University of Technology) (Chalmers University of Technology) (Chalmers University of Technology) (Aalto University) (Chalmers University of Technology) (RWTH Aachen University) (RWTH Aachen University) (Advanced Microelectronic Center Aachen) (Advanced Microelectronic Center Aachen) (Chalmers University of Technology) (Universitat Autònoma de Barcelona)
| Data: | 2020 |
| Resum: | It has been argued that current saturation in graphene field-effect transistors (GFETs) is needed to get optimal maximum oscillation frequency (f ). This paper investigates whether velocity saturation can help to get better current saturation and if that correlates with enhanced f . We have fabricated 500 nm GFETs with high extrinsic f (37 GHz), and later simulated with a drift-diffusion model augmented with the relevant factors that influence carrier velocity, namely: short-channel electrostatics, saturation velocity effect, graphene/dielectric interface traps, and self-heating effects. Crucially, the model provides microscopic details of channel parameters such as carrier concentration, drift and saturation velocities, allowing us to correlate the observed macroscopic behavior with the local magnitudes. When biasing the GFET so all carriers in the channel are of the same sign resulting in highly concentrated unipolar channel, we find that the larger the drain bias is, both closer the carrier velocity to its saturation value and the higher the f are. However, the highest f can be achieved at biases where there exists a depletion of carriers near source or drain. In such a situation, the highest f is not found in the velocity saturation regime, but where carrier velocity is far below its saturated value and the contribution of the diffusion mechanism to the current is comparable to the drift mechanism. The position and magnitude of the highest f depend on the carrier concentration and total velocity, which are interdependent and are also affected by the self-heating. Importantly, this effect was found to severely limit radio-frequency performance, reducing the highest f from ∼60 to ∼40 GHz. |
| Ajuts: | European Commission 785219 European Commission 881603 Agencia Estatal de Investigación RTI2018-097876-B-C21 Ministerio de Economía y Competitividad TEC2015-67462-C2-1-R |
| Nota: | Altres ajuts: with the support of the Secretaria d'Universitats i Recerca of the Departament d'Empresa I Coneixemment of the Generalitat de Catalunya for emerging technology clusters to carry out valorization and transfer of research results (reference of the GraphCAT project: 001-P001702) |
| Drets: | Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, sempre que no sigui amb finalitats comercials, i sempre que es reconegui l'autoria de l'obra original.  |
| Llengua: | Anglès |
| Document: | Article ; recerca ; Versió publicada |
| Publicat a: | Nanoscale advances, Vol. 2, Issue 9 (July 2020) , p. 4179-4186, ISSN 2516-0230 |
