Transitions between channel and contact regimes of low-frequency noise in many-layer MoS2 field effect transistors (original) (raw)
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Experimental and modeling study of 1/f noise in multilayer MoS2 and MoSe2 field-effect transistors
Journal of Applied Physics, 2020
In field-effect transistors (FETs) with two-dimensional (2D) transition metal dichalcogenide channels, the dependence of field-effect mobility on atomic layer thickness has been studied and interpreted in terms of interface scattering and interlayer coupling resistance (Rint). However, a model for 1/f noise, such as in MoS2 and in MoSe2 FETs, for various contact metals and layer number thicknesses has not been reported. In this work, we have experimentally studied current–voltage and 1/f noise on MoS2 and MoSe2 FETs with source and drain contacts of high and low work function metals to understand both the mobility and the noise behavior. We have developed a noise model incorporating layer number dependent Hooge parameters and Rint. The noise and mobility models utilize screening lengths for charge, mobility, and Hooge parameter to describe the variation of these quantities with a layer number. Using our single model topology with appropriate fitting parameters for each material and ...
Microscopic origin of low frequency noise in MoS2 field-effect transistors
APL Materials, 2014
We report measurement of low frequency 1/f noise in molybdenum di-sulphide (MoS 2) field-effect transistors in multiple device configurations including MoS 2 on silicon dioxide as well as MoS 2-hexagonal boron nitride (hBN) heterostructures. All as-fabricated devices show similar magnitude of noise with number fluctuation as the dominant mechanism at high temperatures and density, although the calculated density of traps is two orders of magnitude higher than that at the SiO 2 interface. Measurements on the heterostructure devices with vacuum annealing and dual gated configuration reveals that along with the channel, metal-MoS 2 contacts also play a significant role in determining noise magnitude in these devices.
Correlating Electronic Transport and 1/ f Noise in MoSe2 Field-Effect Transistors
Physical Review Applied, 2018
Two-Dimensional Transition Metal Dichalcogenides (2D-TMDCs) such as MoS 2 , MoSe 2 , WS 2 , and WSe 2 with van der Waal's type interlayer coupling is being widely explored as channel materials in a Schottky Barrier Field Effect Transistor (SB-FET) configuration. While their excellent electrostatic control and high ON/OFF ratios have been identified, a clear correlation between electronic transport and the lowfrequency noise with different atomic layer thickness is missing. For multi-layer channels in MoS 2 FETs, the effects of interlayer coupling resistance on device conductance and mobility have been studied, but no systematic study included interlayer effects in consideration of the intrinsic (channel) and extrinsic (total device) noise behavior. Here we report the 1/f noise properties in MoSe 2 FETs with varying channel thickness (3 to 40 atomic layers). Contributions of channel vs. access/contact regions were extracted from current-voltage (transport) and 1/f noise measurements. The measured noise amplitude shows a direct crossover from channel-to contact-dominated noise as the gate voltage is increased. The results can be interpreted in terms of a Hooge relationship associated with the channel noise, a transition region, and a saturated high-gate voltage regime whose characteristics are determined by a voltage-independent conductance and noise source associated with the metallurgical contact and the interlayer resistance. Both the channel Hooge coefficient and the channel/access noise amplitude decrease with increasing channel thickness over the range of 3 to 15 atomic layers, with the former remaining approximately
2018
Two-Dimensional Transition Metal Dichalcogenides (2D TMDCs) such as MoS2, MoSe2, WS2, and WSe2 with van der Waal’s type interlayer coupling are being widely explored as channel materials in a Schottky Barrier Field Effect Transistor (SB FET) configuration. While their excellent electrostatic control and high on/off ratios have been identified, a clear correlation between electronic transport and the lowfrequency noise with different atomic-layer thickness is missing. For multilayer channels in MoS2 FETs, the effects of interlayer-coupling resistance on device conductance and mobility have been studied, but no systematic study has included interlayer effects in consideration of the intrinsic (channel) and extrinsic (total device) noise behavior. Here, we report the 1/f noise properties in MoSe2 FETs with varying channel thicknesses (3–40 atomic layers). Contributions of channel vs access/contact regions are extracted from current-voltage (transport) and 1/f noise measurements. The me...
Low-Frequency Noise in Bilayer MoS2 Transistor
ACS Nano, 2014
Low-frequency noise is a significant limitation on the performance of nanoscale electronic devices. This limitation is especially important for devices based on twodimensional (2D) materials such as graphene and transition metal dichalcogenides (TMDs), which have atomically thin bodies and, hence, are severely affected by surface contaminants. Here, we investigate the low-frequency noise of transistors based on molybdenum disulfide (MoS 2 ), which is a typical example of TMD. The noise measurements performed on bilayer MoS 2 channel transistors show a noise peak in the gate-voltage dependence data, which has also been reported for graphene. To understand the peak, a trap decay-time based model is developed by revisiting the carrier number fluctuation model. Our analysis reveals that the peak originates from the fact that the decay time of the traps for a 2D device channel is governed by the van der Waals bonds between the 2D material and the surroundings. Our model is generic to all 2D materials and can be applied to explain the V, M and Λ shaped dependence of noise on the gate voltage in graphene transistors, as well as the noise shape dependency on the number of atomic layers of other 2D materials. Since the van der Waals bonding between the surface traps and 2D materials is weak, in accordance with the developed physical model, an annealing process is shown to significantly reduce the trap density, thereby reducing the low-frequency noise.
Low-Frequency 1/f Noise in MoS2 Transistors
2013
We report on the results of the low-frequency (1/f, where f is frequency) noise measurements in MoS 2 field-effect transistors revealing the relative contributions of the MoS 2 channel and Ti/Au contacts to the overall noise level. The investigation of the 1/f noise was performed for both as fabricated and aged transistors. It was established that the McWhorter model of the carrier number fluctuations describes well the 1/f noise in MoS 2 transistors, in contrast to what is observed in graphene devices. The trap densities extracted from the 1/f noise data for MoS 2 transistors, are 1.5 × 10 19 eV -1 cm -3 and 2 × 10 20 eV -1 cm -3 for the as fabricated and aged devices, respectively. It was found that the increase in the noise level of the aged MoS 2 transistors is due to the channel rather than the contact degradation. The obtained results are important for the proposed electronic applications of MoS 2 and other van der Waals materials. #These authors contributed equally to research.
IEEE Electron Device Letters, 2015
We report on the transport and low-frequency noise measurements of MoS 2 thin-film transistors (TFTs) with thin (2-3 atomic layers) and thick (15-18 atomic layers) channels. The back-gated transistors made with the relatively thick MoS 2 channels have advantages of the higher electron mobility and lower noise level. The normalized noise spectral density of the low-frequency 1/ f noise in thick MoS 2 transistors is of the same level as that in graphene. The MoS 2 transistors with the atomically thin channels have substantially higher noise levels. It was established that, unlike in graphene devices, the noise characteristics of MoS 2 transistors with thick channels (15-18 atomic planes) could be described by the McWhorter model. Our results indicate that the channel thickness optimization is crucial for practical applications of MoS 2 TFTs.
Photodoping-Driven Crossover in the Low-Frequency Noise of MoS2 Transistors
Physical Review Applied, 2017
Transition metal dichalcogenide field-effect transistors (FETs) have been actively explored for low-power electronics, light detection, and sensing. Albeit promising, their performance is strongly limited by low-frequency noise (LFN). Here, we report on the study of LFN in MoS2 FETs on SiO2 substrates in ambient conditions using photodoping. Using this external excitation source allows us to access different non-equilibrium steady states and cross over different noise regimes. We observe a dependence of the noise power spectrum with the transient decay time window, approaching 1/f-type when the system is closer to equilibrium, and identify a dependence of the LFN with channel thickness. Monolayer/bilayer devices exhibit random telegraph noise for insulating regimes and 1/f-type Hooge mobility fluctuations (HMF) for conductive regimes. Thicker devices exhibit mainly 1/f-type carrier number fluctuations (CNF). In the latter, we observe a photodoping-induced change from a near parabolic to a near linear dependence of the inverse 1/f noise amplitude above the threshold gate voltage. This change indicates a crossover in the LFN mechanism from CNF to HMF. We demonstrate that the study of conductance and noise under photodoping is an effective tool to identify dominating carrier noise mechanisms in few-atomic-layer FETs for a wide range of doping regimes.