Contact gating at GHz frequency in graphene.

Q Wilmart,J.-M Berroir,N Garroum,M Boukhicha,W Yang,P Morfin,M Rosticher,A Inhofer,G Fève,B Plaçais

doi:10.1038/srep21085

Abstract

The paradigm of graphene transistors is based on the gate modulation of the channel carrier density by means of a local channel gate. This standard architecture is subject to the scaling limit of the channel length and further restrictions due to access and contact resistances impeding the device performance. We propose a novel design, overcoming these issues by implementing additional local gates underneath the contact region which allow a full control of the Klein barrier taking place at the contact edge. In particular, our work demonstrates the GHz operation of transistors driven by independent contact gates. We benchmark the standard channel and novel contact gating and report for the later dynamical transconductance levels at the state of the art. Our finding may find applications in electronics and optoelectronics whenever there is need to control independently the Fermi level and the electrostatic potential of electronic sources or to get rid of cumbersome local channel gates.

Highlights

Contacts behave as passive elements impeding the performance of electronic devices
The independent dual gate control of Klein barriers is highlighted in the low-bias resistance curve R(Vch), where R is strongly modulated by Vcont at large channel p- and n-doping (Fig. 1b) while remaining independent of Vcont at cturhpaaonnnsniscethloanrnse(nugetmrla(/lgiVmtRy,Fd.cshA)∼tafn2ind5i0tceoSbn.mitaa−sc,1tVt(hg−emR1d,)Fc.ounat l)-ggaattienKg,BbTosthhovwalsuaeslaarpgperRoFacthrainngsctohnedsutactteanocf eth(egmRaFrtpfeorr unit width W) RF field effect
Based on the understanding of the DC properties of our dual gate Klein barrier transistors (KBTs), we proceed by investigating its dynamical properties

Summary

Introduction

Contacts behave as passive elements impeding the performance of electronic devices. One can think of turning contacts to active elements by controlling independently and dynamically their electric and chemical potentials using individual contact gates; the non linear element is the Klein tunneling barrier that develops at the contact edge due to the work function mismatch between metal and graphene[8]. Such a contact gating is challenging as it requires a set of local gates to engineer the doping profile all along the graphene sheet with the Fermi wave length resolution. The independent dual gate control of Klein barriers is highlighted in the low-bias resistance curve R(Vch), where R is strongly modulated by Vcont at large channel p- and n-doping (Fig. 1b) while remaining independent of Vcont at cturhpaaonnnsniscethloanrnse(nugetmrla(/lgiVmtRy,Fd.cshA)∼tafn2ind5i0tceoSbn.mitaa−sc,1tVt(hg−emR1d,)Fc.ounat l)-ggaattienKg,BbTosthhovwalsuaeslaarpgperRoFacthrainngsctohnedsutactteanocf eth(egmRaFrtpfeorr unit width W) RF field effect

Methods

Results

Conclusion