Low Frequency Noise Mechanisms Research Articles

Analysis of Low-Frequency 1/f Noise Characteristics for MoTe2 Ambipolar Field-Effect Transistors.

Low-frequency electronic noise is an important parameter used for the electronic and sensing applications of transistors. Here, we performed a systematic study on the low-frequency noise mechanism for both p-channel and n-channel MoTe2 field-effect transistors (FET) at different temperatures, finding that low-frequency noise for both p-type and n-type conduction in MoTe2 devices come from the variable range hopping (VRH) transport process where carrier number fluctuations (CNF) occur. This process results in the broad distribution of the waiting time of the carriers between successive hops, causing the noise to increase as the temperature decreases. Moreover, we found the noise magnitude for p-type MoTe2 FET hardly changed after exposure to the ambient conditions, whereas for n-FET, the magnitude increased by nearly one order. These noise characteristics may provide useful guidelines for developing high-performance electronics based on the emerging transition metal dichalcogenides.

Simulation of low frequency noise in buried-channel MOSFET by a Green’s function-based numerical trap level model

The depletion mode Buried Chanel (BC) MOSFETs are known for their reduced Low Frequency Noise (LFN) as compared with normal Surface Channel (SC) MOSFETs in the application of Charge-Coupled Devices (CCDs) and CMOS imagers. To investigate the BC MOSFETs’ LFN mechanism comprehensively, we have developed a physical-based numerical device level simulator that accounts for the LFN contribution from each single individual oxide trap. During the simulation, the trapping current amplitude ΔID matrices are extracted efficiently by the potential-current based Green’s function. The trap capture and emission time constants are calculated via Shockley–Read–Hall (SRH) theory with Wentzel-Kramers-Brillouin (WKB) tunneling approximation. To valid our simulator, both BC and SC type MOSFETs are designed and fabricated in a CMOS imager compatible process for noise measurement and comparison. Quantitatively agreement has been obtained for both types of MOSFETs in terms of LFN spectra on a wide biasing range from the extracted process-based oxide traps’ geometry and energy sites. It reveals that the low noise operation of BC MOSFETs is inseparable from both the ΔID suppression effect and the traps’ activation energy.

Qubit decoherence under two-axis coupling to low-frequency noises

Many solid-state qubit systems are afflicted by low-frequency noise mechanisms that operate along two perpendicular axes of the Bloch sphere. Depending on the qubit control fields, either noise can be longitudinal or transverse to the quantization axis of the qubit, thus affecting its dynamics in distinct ways, generally contributing to decoherence that goes beyond pure dephasing. Here, we present a theory that provides a unified platform to study dynamics of a qubit subjected to two perpendicular low-frequency noises (assumed to be Gaussian and uncorrelated) under dynamical decoupling pulse sequences. The theory is demonstrated by the commonly encountered case of power law noise spectra, where approximate analytical results can be obtained.

Driven-state relaxation of a coupled qubit-defect system in spin-locking measurements

It is widely known that spin-locking noise-spectroscopy is a powerful technique for the characterization of low-frequency noise mechanisms in superconducting qubits. Here we show that the relaxation rate of the driven spin-locking state of a qubit can be significantly affected by the presence of an off-resonant high-frequency two-level-system defect. Thus, both low- and high-frequency defects should be taken into account in the interpretation of spin-locking measurements and other types of driven-state noise-spectroscopy.

Dimension Scaling Effects on Conduction and Low Frequency Noise Characteristics of ITO-Stabilized ZnO Thin Film Transistors

Conduction characteristics and low frequency noises in ITO-stabilized ZnO thin film transistors (TFTs) with constant channel width (W=50 μm) and different channel lengths (L=5, 10, 25, 50 and 100 μm) are measured and analysis. Firstly, dependences of threshold voltage and field effect mobility on channel length are examined. With decreasing channel length, the threshold voltage shifts to the negative direction which may attribute to carrier diffusion from source/drain to the intrinsic device channel. In addition, significant degradation of field effect mobility is observed in short channel device which are induced by the presence of series contact resistance. The value of contact resistance has also been extracted. Secondly, the drain current noise power spectral densities (S ID ) are measured at varied effective gate voltages. The measured noises follow a 1/f γ and y is about -1.1. Moreover, the normalized noises (S ID /I ds ) are dependent linearly on the inverse of channel length and the slope is about -0.75. Finally, the dominant mechanism of low frequency noise in ITO-stabilized ZnO thin film transistor are examined. The slope of normalized noise against effective gate voltage are extracted, which are varied from -1.03 to -1.84 with decreasing channel length and thus it indicates that ITO-stabilized ZnO TFTs varied from bulk dominated devices to interface dominated devices. By using of ΔN-Δμ model, the normalized noises are simulated by considering of contact resistance. Several noise parameters (flat-band voltage noise spectral density, etc) are extracted and analysis.

Low-Frequency Noise Characteristics in Multilayer MoTe2 FETs With Hydrophobic Amorphous Fluoropolymers

This letter investigates the low-frequency noise (LFN) properties of the multilayer MoTe2 field-effect transistors (FETs) before and after hydrophobic amorphous polymer (CYTOP) encapsulation in the subthreshold and linear regimes. The noise spectrum density of drain current (SID) shows that the LFN in the multilayer MoTe2 FETs nicely fits to a 1/ $f^{\gamma }$ power law with $\gamma \sim \textsf {1}$ in the frequency range of 10–200 Hz. From the dependence of SID on the drain current, carrier number fluctuation ( $\Delta n$ ) is considered as a dominant LFN mechanism from all operation regimes in the multilayer MoTe2 FETs. Extracted trap density (Nt) based on the McWhorter model in this letter was reduced at least more than one order level compared with the multilayer MoTe2 FETs without CYTOP passivation.

Photodoping-Driven Crossover in the Low-Frequency Noise of MoS2 Transistors

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 MoS$_2$ FETs on SiO$_2$ 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.

Mechanisms of current fluctuation in ambipolar black phosphorus field-effect transistors.

Multi-layer black phosphorus has emerged as a strong candidate owing to its high carrier mobility with most of the previous research work focused on its p-type properties. Very few studies have been performed on its n-type electronic characteristics which are important not only for the complementary operation for logic, but also crucial for understanding the carrier transport through the metal-black phosphorus junction. A thorough understanding and proper evaluation of the performance potential of both p- and n-types are highly desirable. In this paper, we investigate the temperature dependent ambipolar operation of both electron and hole transport from 300 K to 20 K. On-currents as high as 85 μA μm(-1) for a 0.2 μm channel length BP nFET at 300 K are observed. Moreover, we provide the first systematic study on the low frequency noise mechanisms for both n-channel and p-channel BP transistors. The dominated noise mechanisms of the multi-layer BP nFET and pFET are mobility fluctuation and carrier number fluctuations with correlated mobility fluctuations, respectively. We have also established a baseline of the low electrical noise of 8.1 × 10(-9)μm(2) Hz(-1) at 10 Hz at room temperature for BP pFETs, which is 3 times improvement over previous reports, and 7.0 × 10(-8)μm(2) Hz(-1) for BP nFETs for the first time.

Study on interface characteristics in amorphous indium–gallium–zinc oxide thin-film transistors by using low-frequency noise and temperature dependent mobility measurements

In this work, the interface properties of amorphous indium–gallium–zinc oxide thin film transistors annealed at different temperatures ranging from 150 to 250°C are studied by temperature dependent mobility and low-frequency noise (LFN) characterizations. The dominant scattering mechanism for carrier transport is found to be Coulomb scattering based on gate bias and temperature dependent mobility measurement. Meanwhile, as the annealing temperature increases, the dominant mechanism of LFN within the device channel varies from carrier number fluctuation to carrier mobility fluctuation. The border trap density as well as the distribution properties of charged border traps is deduced. The present results suggest that annealing at higher temperature has a more remarkable effect on removing deeper border traps than traps closer to the channel/dielectric interface.

Low frequency noise characteristics in multilayer WSe2 field effect transistor

This paper investigates the low-frequency noise properties of multilayer WSe2 field effect transistors (FETs) in subthreshold, linear, and saturation regime. The measured noise power spectral density of drain current (SID) shows that the low-frequency noise in multilayer WSe2 FET fits well to a 1/fγ power law with γ ∼ 1 in the frequency range of 10 Hz–200 Hz. From the dependence of SID on the drain current, carrier mobility fluctuation is considered as a dominant low frequency noise mechanism from all operation regimes in multilayer WSe2 FET. Extracted Hooge's parameter in this study is within the value of 0.12, comparable to those of the transition metal dichalcogenide FETs in recent reports.

In depth static and low-frequency noise characterization of n-channel FinFETs on SOI substrates at cryogenic temperature

The impact of cryogenic temperature operation (10K) on the short channel effects and low frequency noise was analysed on strained and unstrained n-channel FinFET transistors fabricated on silicon on insulator (SOI) substrates in order to evaluate the devices static performances and to study the low frequency noise mechanisms. The main electrical parameters are investigated and it is evidenced that even at very low temperatures, the strain-engineering techniques boost the devices performances in terms of mobility, threshold voltage, access resistances and drain saturation currents. The DIBL effect, Early voltage and the intrinsic gain are ameliorated only for the short channel devices. A drawback, however, is that slightly improved turn-on capabilities may be noted for standard channel devices compared to strained ones. Low frequency noise measurements show that the carrier number fluctuations dominate the flicker noise in weak inversion even at 10K operation. Access resistance noise contributions were evidenced in strong inversion.

DC and low frequency noise performances of SOI p-FinFETs at very low temperature

In this paper, DC and noise measurements on strained and unstrained SOI p-FinFETs were performed at cryogenic temperatures (10K) in order to evaluate the device performances and study the low frequency noise mechanisms. The main electrical parameters (threshold voltage, subthreshold swing, mobility, etc.) are investigated and compared to those found at 80K and 300K. The low frequency noise analysis clearly shows that from 300K to 10K, the carriers number fluctuation dominates the flicker noise in the channel in weak inversion, while the access resistances noise contribution prevails in strong inversion. 1/fγ noise has been observed with γ varying with the temperature, which implies a non-uniformity of the active trap density in the oxide depth. The noise of the access resistances at 300K originates from mobility fluctuations, while at low temperature operation it seems to have a trapping–detrapping origin.

Low-frequency noise radiation from traffic-induced vibration of steel double-box girder bridge

Low-frequency noise radiated from bridge vibrations has been reported as an environmental noise problem in many countries. In order to investigate the mechanism of low-frequency noise radiated from bridge vibration, a steel bridge with a double-box is adopted for study. Modal parameters of the bridge, including natural frequency, damping ratio and mode shape, are identified from field tests by a combination of Eigensystem Realization Algorithm and Fast Fourier Transformation. Then the grillage model of the bridge is established and physics parameters of the model are updated by genetic algorithm according to identified natural frequencies. The dynamic response of the bridge by the action of a moving vehicle is calculated and assumed as the sound source of low-frequency noise. Then low-frequency noise due to bridge vibration is estimated according to sound wave propagation theories. The validity of the numerical method is verified through comparison with experimental results. Furthermore, noise reduction methods are proposed and corresponding effects are discussed. Results show that numerical simulation is feasible in assessing low-frequency noise due to traffic induced vibration of a bridge, which offers a possible way for environmental assessment as well as being a good reference for noise reduction design of bridges. The deck plate of the bridge is the primary source of low-frequency noise. Hence, increasing the stiffness of a deck plate is effective for noise control. Improving the road roughness can also reduce low-frequency noise.

Impact of High-k HfO2 Dielectric on the Low-Frequency Noise Behaviors in Amorphous InGaZnO Thin Film Transistors

We have investigated the impact of high-k HfO2 gate dielectric on the low-frequency noise (LFN) behaviors of amorphous indium–gallium–zinc oxide thin-film transistors by comparing the LFNs of devices with SiO2 and HfO2 dielectrics. Measured LFNs are nearly 1/ f type for both devices, but the normalized noise for the HfO2 device is around one order of magnitude higher than that for the SiO2 device. The bulk mobility fluctuation is considered as the dominant LFN mechanism in both devices, and the increased LFN in the HfO2 device is attributed to the enhanced mobility fluctuation by the remote phonon scattering from the HfO2.

Low-Frequency Noise Performance of a Bilayer InZnO–InGaZnO Thin-Film Transistor for Analog Device Applications

In this letter, we present a comparative study of the low-frequency noise behavior of single-layer InGaZnO and bilayer InZnO-InGaZnO thin-film transistors (TFTs). The normalized noise for the bilayer oxide TFT is three times lower than that for the single-layer oxide TFT, mainly due to the higher mobility of the thin interfacial InZnO layer. The carrier number fluctuation is the dominant low-frequency noise mechanism in both devices. The use of a high-mobility bilayer oxide TFT with scaled gate length is still valid for reducing low-frequency noise.

Comparative Study of the Low-Frequency-Noise Behaviors in a-IGZO Thin-Film Transistors With $\hbox{Al}_{2}\hbox{O}_{3}$ and $\hbox{Al}_{2}\hbox{O}_{3}/\hbox{SiN}_{x}$ Gate Dielectrics

A comparative study is made of the low-frequency noise (LFN) in amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs) with Al2O3 and Al2O3/SiNx gate dielectrics. The LFN is proportional to 1/fgamma, with gamma ~ 1 for both devices, but the normalized noise for the Al2O3/SiNx device is two to three orders of magnitude lower than that for the Al2O3 device. The mobility fluctuation is the dominant LFN mechanism in both devices, but the noise from the source/drain contacts becomes comparable to the intrinsic channel noise as the gate overdrive voltage increases in Al2O3/SiNx devices. The SiNx interfacial layer is considered to be very effective in reducing LFN by suppressing the remote phonon scattering from the Al2O3 dielectric. Hooge's parameter is extracted to ~6.0 times 10-3 in Al2O3/SiNx devices.

Low-Frequency Noise in Amorphous Indium–Gallium–Zinc-Oxide Thin-Film Transistors

We have investigated the low-frequency noise (LFN) properties of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) as a function of frequency, bias, and channel length of devices. The measured noise power spectral density of drain current (S iD) shows that the low-frequency noise in a-IGZO TFTs obeys the classical 1/f noise theory, i.e., it fits well to a 1/f gamma power law with gamma ~ 1 in the frequency range of 10 Hz to 1 kHz. From the dependence of normalized noise power spectral density (S iD/ID 2) on the gate voltage, mobility fluctuation is considered as a dominant LFN mechanism in a-IGZO TFTs. The magnitude of S iD/ID 2 is inversely proportional to the channel length of devices, which indicates that contact noise is insignificant in a-IGZO TFTs.

Effect of nitrogen incorporation on 1/f noise performance of metal-oxide-semiconductor field effect transistors with HfSiON dielectric

Nitrided hafnium silicate is the leading candidate for possible replacement of SiON as a gate dielectric. 1/f noise characteristics of plasma and thermally nitrided Hf-based high-dielectric constant (high-k) gate dielectrics were investigated. Plasma nitrided samples showed less noise than thermally nitrided samples. The mobility fluctuation component of 1/f noise was found to show a strong process dependence, specifically on the nitridation technique. Increase in the number of Coulomb scattering sites due to the additional Si–N bonds near the high-k/Si interface is suggested as the reason for this dependence. This work represents the first investigation on the effect of different nitridation methodologies on low-frequency noise mechanisms in ultrathin (∼2 nm) Hf-based high-k nMOSFET (metal-oxide-semiconductor field effect transistor).

Low-frequency noise mechanisms in Si and pseudomorphic SiGe p-channel field-effect transistors

Measurements of low frequency noise in Si and Si0.64Ge0.36 p-channel metal oxide semiconductor field effect transistors are compared with a model of carrier number fluctuations due to tunneling into an energy independent density of oxide trap states (Nox) and associated mobility fluctuations. The failure of the model to explain the data leads us to suggest that reduced noise in the SiGe device as compared to Si is primarily associated with an energy dependence of Nox and a displacement of the Fermi level at the SiO2 interface in the heterostructure relative to the Si control.

On the low frequency noise mechanisms in GaN/AlGaN HFETs

The low frequency noise in GaN/AlGaN heterostructure field effect transistors (HFETs) was studied in the temperature range from 8 to 300 K. At gate biases close to the threshold, the noise came from the device region under the gate, and the Hooge parameter αch was inversely proportional to ns (α ∼ 1/ns) in the entire temperature range. This dependence might be explained by electron tunnelling from the 2D gas into the traps in the adjoining GaN or AlGaN layers. At voltages close to zero, the ungated source-gate and gate-drain regions were responsible for the noise, and the Hooge constant was two orders of magnitude larger. This result is consistent with recent studies of the mechanism of the current collapse in GaN-based FETs. A notable contribution from the generation-recombination noise with activation energy 0.24 eV was observed in the temperature interval from 50 K to 150 K.