Channel-Length-Dependent Transport Behaviors of Graphene Field-Effect Transistors

Abstract

Abstract-This letter presents a detailed study of transport in graphene field-effect transistors (GFETs) with various channel lengths, from 5 μm down to 90 nm, using transferred graphene grown by chemical vapor deposition. An electron-hole asymmetry observed in short-channel devices suggests a strong impact from graphene/metal contacts. In addition, for the first time, we observe a shift of the gate voltage at the Dirac point in graphene devices as a consequence of gate length scaling. The unusual shift of the Dirac point voltage has been identified as one of the signatures of short-channel effects in GFETs.

Pseudosaturation and Negative Differential Conductance in Graphene Field-Effect Transistors

“…This short-channel effect is due to the reduced gate charge control at short gate length: It becomes necessary to apply a more negative V GS to push electrons out of the channel and reach the equilibrium between electrons and holes. This effect is obviously stronger when increasing W IN , as experimentally observed in [43]. Additionally, the off-current increases when reducing L G .…”

Optimizing the fabrication process for high performance graphene field effect transistors

“…The Dirac point was found to shift positively when the drain voltage increase from À1 V to 1 V. The drain induced Dirac point shifting was also observed by recent publications [14,15], which was because of the drain induced channel potential weaken the gate control. For graphene FETs, the Dirac point happens where the electron/hole carrier injection at source and drain balance with each other, this requires the Dirac point shift according to the following relation when the source/drain voltage V D increase from V 1 D to V 2 D : V 2 dirac À V 1 dirac ¼ 1=2ðV 2 D À V 1 D Þ.…”

“…The work function of Pd is 5.1 eV, which is larger comparing with the work function of graphene (4.5 eV). This is supposed to dope the graphene underneath the metal to be p-type [14]. When the graphene in the channel region is shifted by the gate to n region, a p-n junction is formed with the contact and will limit the current injection and decrease the current level of electron branch, which results a low electron mobility extracted form g m method.…”

Transport behaviors in graphene field effect transistors on boron nitride substrate

“…the transition between normal transmission above the barrier and chiral tunneling through the barrier. This short channel effect is obviously stronger when increasing t ox • It was experimentally observed in [21].…”