Tunneling Times in Graphene FET: From Fundamental Physics to Practical Engineering

Because of its large Fermi velocity, graphene is expected to play an important role in the future of (small signal) radio frequency electronics. The connection between the Klein tunneling times of electrons and cut-off frequencies of graphene devices is not obvious. We argue in this paper that the trajectory-based Bohmian approach gives a very natural framework to quantify Klein tunneling times because of its ability to distinguish, not only between transmitted and reflected electrons, but also between reflected electrons that spend time in the barrier and those that do not. In particular, we study Klein tunneling times for electrons in a two-terminal graphene device constituted by a potential barrier between two metallic contacts. The main conclusion of this work is that the high graphene mobility is roughly independent of the presence of Klein tunneling phenomena in the active device region. Finally, the connection between transit (tunneling) times and cut-off frequencies in electronic devices is discussed.