Abstract
Our focus in this study is on characterizing the capacitance voltage (C-V) behavior of Bernal stacking bilayer graphene (BG) and trilayer graphene (TG) as the channel of FET devices. The analytical models of quantum capacitance (QC) of BG and TG are presented. Although QC is smaller than the classic capacitance in conventional devices, its contribution to the total metal oxide semiconductor capacitor in graphene-based FET devices becomes significant in the nanoscale. Our calculation shows that QC increases with gate voltage in both BG and TG and decreases with temperature with some fluctuations. However, in bilayer graphene the fluctuation is higher due to its tunable band structure with external electric fields. In similar temperature and size, QC in metal oxide BG is higher than metal oxide TG configuration. Moreover, in both BG and TG, total capacitance is more affected by classic capacitance as the distance between gate electrode and channel increases. However, QC is more dominant when the channel becomes thinner into the nanoscale, and therefore we mostly deal with quantum capacitance in top gate in contrast with bottom gate that the classic capacitance is dominant.
Highlights
As the fundamental miniaturization limits of integrated metal oxide (MOS) processes are being approached, the conventional path of scaling integrated processes, obeying Moore’s law and correspondingly leading to smaller gate lengths and oxide thicknesses, is no longer meeting the performance and power consumption requirements [1]
Each of bilayer graphene (BG) and trilayer graphene (TG) when applied as channel in FET devices shows different behavior compared to each other and monolayer graphene
Rather than a linear band structure as observed in monolayer graphene, the band gap could be tuned in BG and band overlap could be varied in TG
Summary
As the fundamental miniaturization limits of integrated metal oxide (MOS) processes are being approached, the conventional path of scaling integrated processes, obeying Moore’s law and correspondingly leading to smaller gate lengths and oxide thicknesses, is no longer meeting the performance and power consumption requirements [1]. In nanoscale devices with strongly coupled gates, the quantum capacitance (QC) as high as hundreds of attofarads could be obtained due to a low density of states in the channel [10]. We present the mathematical model of capacitance where intrinsic AB bilayer graphene or ABA Trilayer graphene is used as channel of FET devices in low energy regime with respect to classical (electrostatic) and quantum aspects. Their behavior under different gate voltage as well as temperature dependence will be studied. The behavior of quantum capacitance in BG and TG will be compared and discussed, and the effect of the distance between the center of the channel and the gate electrodes (top and bottom) on total capacitance will be argued
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