Charge Noise in Graphene Transistors (original) (raw)
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Low-Frequency Noise in Graphene Transistors
2009
We present the results of the experimental investigation of the low-frequency noise in three-terminal bilayer graphene devices. The quality of graphene layers has been verified with micro-Raman spectroscopy. Back-gated devices were fabricated using electron beam lithography and evaporation. The back-gate was used to adjust electrical conductivity through the graphene layer placed on top of Si/SiO 2 substrate. The charge neutrality point for examined devices was∼10 V. The noise spectral density was rather low (on the order of ∼10E −23-10E −22 A 2 /Hz at frequency of 1 kHz).The noise reveals generationrecombination (G-R) bulges. Presence of G-R bulges and deviation from the 1/f spectrum suggest that the noise is of carrier-number fluctuation origin due to carrier trapping by defects [1].The low values of the low-frequency noise add validity to the proposed electronic applications of graphene. [1] Q. Shao et al., IEEE EDL (2008).
Journal of Physics: Condensed Matter, 2010
We fabricated a large number of single and bilayer graphene transistors and carried out a systematic experimental study of their low-frequency noise characteristics. Special attention was given to determining the dominant noise sources in these devices and the effect of aging on the current-voltage and noise characteristics. The analysis of the noise spectral density dependence on the area of graphene channel showed that the dominant contributions to the low-frequency electronic noise come from the graphene layer itself rather than from the contacts. Aging of graphene transistors due to exposure to ambient conditions for over a month resulted in substantially increased noise, attributed to the decreasing mobility of graphene and increasing contact resistance. The noise spectral density in both single and bilayer graphene transistors either increased with deviation from the charge neutrality point or depended weakly on the gate bias. This observation confirms that the low-frequency noise characteristics of graphene transistors are qualitatively different from those of conventional silicon metal-oxide-semiconductor field-effect transistors.
Understanding the bias dependence of low frequency noise in single layer graphene FETs
Nanoscale, 2018
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...
Effect of Spatial Charge Inhomogeneity on 1/f Noise Behavior in Graphene
Scattering mechanisms in graphene are critical to understanding the limits of signal-to-noise ratios of unsuspended graphene devices. Here we present the four-probe low-frequency noise (1/f) characteristics in back-gated single layer graphene (SLG) and bilayer graphene (BLG) samples. Contrary to the expected noise increase with the resistance, the noise for SLG decreases near the Dirac point, possibly due to the effects of the spatial charge inhomogeneity. For BLG, a similar noise reduction near the Dirac point is observed, but with a different gate dependence of its noise behavior. Some possible reasons for the different noise behavior between SLG and BLG are discussed.
Characterization and Modeling of Graphene Transistor Low-Frequency Noise
IEEE Transactions on Electron Devices, 2012
This brief presents low-frequency noise measurements on a graphene field-effect transistor with graphene layer decomposed from SiC substrate. The measurements indicate the predominance of flicker noise in the current noise source measured between drain and source with quadratic dependence with a drain current. The noise level is inversely proportional to the channel area indicating the location of the main noise source to be in graphene layer. From these measurements, the main noise sources, including the main flicker noise and the Johnson noise contributions, have been introduced in a compact model. This compact model has been built using dc characterization results. Finally, the noise compact model has been validated through comparison to noise measurement.
Low-frequency electronic noise in the double-gate single-layer graphene transistors
Applied Physics Letters, 2009
The authors report the results of an experimental investigation of the low-frequency noise in the double-gate graphene transistors. The back-gate graphene devices were modified via addition of the top gate separated by ϳ20 nm of HfO 2 from the single-layer graphene channels. The measurements revealed low flicker noise levels with the normalized noise spectral density close to 1 / f ͑f is the frequency͒ and Hooge parameter ␣ H Ϸ 2 ϫ 10 −3 . The analysis of noise spectral density dependence on the top and bottom gate biases helped to elucidate the noise sources in these devices. The obtained results are important for graphene electronic and sensor applications.
Electrical Noise and Transport Properties of Graphene
Journal of Low Temperature Physics, 2013
We present a study of the noise properties of single-layer exfoliated graphene as a function of gate bias. A tunnel/trap model is presented based on the interaction of graphene electrons with the underlying substrate. The model incorporates trap position, energy, and barrier height for tunneling into a given trap-along with the band-structure of the graphene-and is in good accord with the general characteristics of the data.
Noise in graphene and carbon nanotube devices
21th International Conference on Noise and Fluctuations, 2011
We discuss the shot noise properties of carbon-based transistors in which the channel is laterally confined, either in the form of graphene nanoribbons or of carbon nanotubes. We show with an simple compact model and with computationallyintensive statistical simulations that electron-electron interaction can lead to a significant suppression of shot noise, often overlooked when the device is described with the Landauer-Buttiker formalism. Finally, we show that interband tunneling can play a significant role in enhancing shot noise due to exchange of holes between drain and channel, that is a peculiar effect observable in the case of channel materials with very small energy gaps.
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.
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...