aalto1 untyped-item.component.html
Does carrier velocity saturation help to enhance f(max) in graphene field-effect transistors?
Loading...
Access rights
openAccess
publishedVersion
URL
Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
This publication is imported from Aalto University research portal.
View publication in the Research portal (opens in new window)
View/Open full text file from the Research portal (opens in new window)
View publication in the Research portal (opens in new window)
View/Open full text file from the Research portal (opens in new window)
Unless otherwise stated, all rights belong to the author. You may download, display and print this publication for Your own personal use. Commercial use is prohibited.
Date
Major/Subject
Mcode
Degree programme
Language
en
Pages
8
Series
Nanoscale Advances, Volume 2, issue 9, pp. 4179-4186
Abstract
It has been argued that current saturation in graphene field-effect transistors (GFETs) is needed to get optimal maximum oscillation frequency (f(max)). This paper investigates whether velocity saturation can help to get better current saturation and if that correlates with enhancedf(max). We have fabricated 500 nm GFETs with high extrinsicf(max)(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 thef(max)are. However, the highestf(max)can be achieved at biases where there exists a depletion of carriers near source or drain. In such a situation, the highestf(max)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 highestf(max)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 highestf(max)from similar to 60 to similar to 40 GHz.
Description
| openaire: EC/H2020/785219/EU//GrapheneCore2 | openaire: EC/H2020/881603/EU//GrapheneCore3
Other note
Citation
Feijoo, P C, Pasadas, F, Bonmann, M, Asad, M, Yang, X, Generalov, A, Vorobiev, A, Banszerus, L, Stampfer, C, Otto, M, Neumaier, D, Stake, J & Jimenez, D 2020, 'Does carrier velocity saturation help to enhance f(max) in graphene field-effect transistors?', Nanoscale Advances, vol. 2, no. 9, pp. 4179-4186. https://doi.org/10.1039/c9na00733d