Electrical and noise characteristics of graphene field-effect transistors: ambient effects, noise sources and physical mechanisms (original) (raw)
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This letter investigates the bias-dependent low frequency noise of single layer graphene field-effect transistors. Noise measurements have been conducted with electrolyte-gated graphene transistors covering a wide range of gate and drain bias conditions for different channel lengths. A new analytical model that accounts for the propagation of the local noise sources in the channel to the terminal currents and voltages is proposed in this paper to investigate the noise bias dependence. Carrier number and mobility fluctuations are considered as the main causes of low frequency noise and the way these mechanisms contribute to the bias dependence of the noise is analyzed in this work. Typically, normalized low frequency noise in graphene devices has been usually shown to follow an M-shape dependence versus gate voltage with the minimum near the charge neutrality point (CNP). Our work reveals for the first time the strong correlation between this gate dependence and the residual charge w...
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IET circuits, devices & systems, 2015
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Current crowding mediated large contact noise in graphene field-effect transistors
Nature communications, 2016
The impact of the intrinsic time-dependent fluctuations in the electrical resistance at the graphene-metal interface or the contact noise, on the performance of graphene field-effect transistors, can be as adverse as the contact resistance itself, but remains largely unexplored. Here we have investigated the contact noise in graphene field-effect transistors of varying device geometry and contact configuration, with carrier mobility ranging from 5,000 to 80,000 cm(2 )V(-1 )s(-1). Our phenomenological model for contact noise because of current crowding in purely two-dimensional conductors confirms that the contacts dominate the measured resistance noise in all graphene field-effect transistors in the two-probe or invasive four-probe configurations, and surprisingly, also in nearly noninvasive four-probe (Hall bar) configuration in the high-mobility devices. The microscopic origin of contact noise is directly linked to the fluctuating electrostatic environment of the metal-channel int...
Microwave noise characterization of graphene field effect transistors
Applied Physics Letters, 2014
The microwave noise parameters of graphene field effect transistors (GFETs) fabricated using chemical vapor deposition graphene with 1 lm gate length in the 2 to 8 GHz range are reported. The obtained minimum noise temperature (T min) is 210 to 610 K for the extrinsic device and 100 to 500 K for the intrinsic GFET after de-embedding the parasitic noise contribution. The GFET noise properties are discussed in relation to FET noise models and the channel carrier transport. Comparison shows that GFETs can reach similar noise levels as contemporary Si CMOS technology provided a successful gate length scaling is performed. V
ACS Applied Materials & Interfaces
Substrate plays a crucial role in determining transport and low frequency noise behavior of graphene field effect devices. Typically, heavily dope Si/SiO2 substrate is used to fabricate these devices for efficient gating. Trapping-detrapping processes closed to the graphene/substrate interface are the dominant sources of resistance fluctuations in the graphene channel, while Coulomb fluctuations arising due to any remote charge fluctuations inside the bulk of the substrate are effectively screened by the heavily doped substrate. Here, we present electronic transport and low frequency noise characteristics of large area CVD graphene field effect transistor (FET) prepared on a lightly doped Si/SiO2 substrate (NA ≈ 10 15 cm-3). Through a systematic characterization of transport, noise and capacitance at various temperature, we reveal that remote Si/SiO2 interface can affect the charge transport in graphene severely and any charge fluctuations inside bulk of the silicon substrate can be sensed by the graphene channel. The resistance (R) vs. back gate voltage (Vbg) characteristics of the device shows a hump around the depletion region formed at the SiO2/Si interface, confirmed by the capacitance (C)-Voltage (V) measurement. Low frequency noise measurement on these fabricated devices shows a peak in the noise amplitude close to the depletion region. This indicates that due to the absence of any charge layer at Si/SiO2 interface, screening ability decreases and as a consequence, any fluctuations in the deep level coulomb impurities inside the silicon substrate can be observed as a noise in resistance in graphene channel via mobility fluctuations. Noise behavior on ionic liquid gated graphene on the same substrate exhibits no such peak in noise and can be explained by the interfacial trappingdetrapping processes closed to the graphene channel. Our study will definitely be useful for integrating graphene with the existing silicon technology, in particular, for high frequency applications.