Time Flow in Graphene and Its Implications on the Cutoff Frequency of Ballistic Graphene Devices

TL;DR

This paper reveals that the traversal time in ballistic graphene devices is significantly affected by contact effects, leading to lower performance than previously believed, due to electron transformation phenomena.

Contribution

It demonstrates that contact-induced electron transformations slow down carrier traversal time and reduce transmission, challenging common assumptions in ballistic graphene device modeling.

Findings

Traversal time is slower when contact effects are included.

Transmission at normal incidence is less than 1 due to contact effects.

Device performance is lower than previously estimated.

Abstract

This manuscript deals with time flow in ballistic graphene devices. It is commonly believed that in the ballistic regime the traversal time of carriers in gated graphene at normal incidence is just the ratio of the length of the device and the Fermi velocity. However, we show that the traversal time is much slower if the influence of metallic contacts on graphene is considered. Even the transmission at normal incidence becomes smaller than 1, contradicting yet another common belief. These unexpected effects are due to the transformation of Schrodinger electrons in the metallic contact into Dirac electrons in graphene and vice versa. As a direct consequence of these transformations, the ultimate performance of gated ballistic devices are much lower than expected, in agreement with experimental results.