Origin Of Low-frequency Noise Research Articles

Origin of Low-Frequency Noise in Si n-MOSFET at Cryogenic Temperatures: The Effect of Interface Quality

Origin of Low-Frequency Noise in Si n-MOSFET at Cryogenic Temperatures: The Effect of Interface Quality

A Study on Dominant Mechanism and Analytical Model of Low-Frequency Noise in FD-SOI pTFET

The origin of low-frequency noise (LFN) properties and the accuracy of LFN model were demonstrated in a fully depleted silicon-on-insulator p-type tunneling field-effect transistor (pTFET). We demonstrated that the origin of LFN properties in pTFET can be deduced and analyzed via the current fluctuation induced by tunneling in the pTFET operation region. Since the trap sites near the tunneling junction contributed to LFN, pTFET must consider the tunneling junction characteristics and channel transportation influences. The tunneling path was not formed at low |VGS| and the carrier transport in pTFET crossed the energy band by Shockley-Read-Hall (SRH) generation-recombination or the trap-assisted tunneling (TAT) mechanism and not through band-to-band tunneling (BTBT). However, with the increase in |VGS|, the tunneling path was formed and the carriers could flow through the energy band by BTBT. The correlation between the simulated model data and experimental data was examined, confirming that the proposed small-signal model accurately represents noise in pTFETs.

(Invited) Review of Identification Methods of 1/f Noise Mechanisms in Polymer-Based OTFTs

We study the low frequency noise, also known as flicker noise (1/f), in polymer-based Organic Thin Film Transistors, and we review techniques to identify the mechanisms of the 1/f noise based on a specific model of the device. We found that the quality of the gate dielectric and its interface may determine the dominant noise mechamism.Three theories have been formulated to explain the origin of 1/f noise in FET devices: the carrier number fluctuation (∆N) theory[1], the mobility fluctuation (∆µ) theory [2], and the ∆N - ∆µ theory [3], which assumes that effects of insulator charge fluctuations affect the carrier mobility at the interface. The ∆N - ∆µ theory reduces to the ∆N model when the surface mobility is not affected by carrier number fluctuation.According to the ∆N - ∆µ theory [3]the plot of SID(f)/ID 2 and [gm/ID]2 against ID (gm being the transconductance and ID the drain current) allows us to identify the noise mechanism. When both curves are parallel, 1/f noise must be due to carrier number fluctuation. If there is a slight deviation from this parallel behavior, it must be due to the correlated surface mobility fludtuation (∆N - ∆µ model).A number of analysis of the noise in OTFTs have been published. In most of them, it is found to be a bulk phenomenon[4,5], and as a result the main mechanism is assumed to be mobility fluctuation. However, very often these analysis are not very complete and are based on crystalline MOSFET models instead of specific OTFT models. On the other hand, it was demonstrated that the analysis must be made over a range wide of bias in order to accurately determine the origin of noise [6,7].We studied the origin of 1/f noise two polymeric p-type OTFT technologies developed by CEA´Liten (France).We found that in the older technology the slopes, in log-log scale, of SID(f)/ID 2 and [gm/ID]2, versus ID had quite different values. This means that the main mechanism of noise in OTFTs is not the fluctuation of the number of carriers. Plotting SID(f)/I2 Dvs (VGS-Vth) in log-log scale (Vth being the threshold voltage) for devices with different channel lengths, channel width W=2000 µm and at VDS = 1 V, we observed that the extracted slope is close to -1 (Table 1). This indicates that noise is due to the fluctuation of carrier mobility, due to the lower quality of the materials and fabrication defects. The threshold voltage was extracted assuming a physically-based OTFT model with a power-law based model of the field effect mobility [8].In the second technology, mobility values are higher, 2-3 cm2/(V s). The normalized current noise PSD follows the squared-transconductance ratio variation (Fig. 1), not the inverse of the drain current. We concluded that the low frequency in the targeted devices of the second technology is originated from the carrier number fluctuation due to trapping/release of charge carriers by trap states uniformly distributed within the gate oxide. The extracted values of gate dielectric trap-states density are comparable to values obtained in conventional Si-based MOSFETs [7], indicating the higher quality of the gate dielectric and its interface with the polymeric material compared to the first studied technology and other previously reported OTFT devices.[1] McWhorter A. L.. "1/f noise and germanium surface prosperities," Semiconductor Surface Physics. R. H. Kingdton (Ed), University of Pennsylvania Press, Philadelphia, PA, 1957, pp. 207-228.[2] Hooge F. N., "1/f noise is no surface effect", Physics Letters, 29A (3), 1969, 139–140[3] Ghibaudo, G., et al..,‘Improved analysis of low frequency noise in field-effect MOS transistors’, Phys. Status Solidi. A , 1991, 124, pp. 571-581[4] L. Ke, S., et al., “Low frequency noise analysis on organic thin film transistors,” Journal of Applied Physics 104, 124502 (2008).[5] H. Kang and V. Subramanian, “Measurement and analysis of 1/f noise under switched bias in organic thin film transistors,” Applied Physics Letters 104, 023301 (2014).[6] Y. Xu, et al., “Origin of low-frequency noise in pentacene field-effect transistors,” Solid-State Electronics 61, 106–110 (2011).[7] W. E. Muhea, et al.. “1/f noise analysis in high mobility polymer-based OTFTs with non-fluorinated dielectric,” Appl. Phys. Lett. 114, 243301 (2019).[8] C.H. Kim; et al., “A Compact Model for Organic Field-Effect Transistors With Improved Output Asymptotic Behaviors,” IEEE Trans. on Electron Devices, vol. 60, no. 3, pp. 1136-1141, March 2013. Figure 1

Observation of directly interacting coherent two-level systems in an amorphous material.

Parasitic two-level tunnelling systems originating from structural material defects affect the functionality of various microfabricated devices by acting as a source of noise. In particular, superconducting quantum bits may be sensitive to even single defects when these reside in the tunnel barrier of the qubit’s Josephson junctions, and this can be exploited to observe and manipulate the quantum states of individual tunnelling systems. Here, we detect and fully characterize a system of two strongly interacting defects using a novel technique for high-resolution spectroscopy. Mutual defect coupling has been conjectured to explain various anomalies of glasses, and was recently suggested as the origin of low-frequency noise in superconducting devices. Our study provides conclusive evidence of defect interactions with full access to the individual constituents, demonstrating the potential of superconducting qubits for studying material defects. All our observations are consistent with the assumption that defects are generated by atomic tunnelling.

Microscopic origin of low frequency noise in MoS2 field-effect transistors

We report measurement of low frequency 1/f noise in molybdenum di-sulphide (MoS2) field-effect transistors in multiple device configurations including MoS2 on silicon dioxide as well as MoS2-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 SiO2 interface. Measurements on the heterostructure devices with vacuum annealing and dual gated configuration reveals that along with the channel, metal-MoS2 contacts also play a significant role in determining noise magnitude in these devices.

Phase noise modeling in LC oscillators implemented in SiGe technology

This paper addresses phase noise analysis of a radiofrequency LC oscillator built around a SiGe heterojunction bipolar transistor (HBT) realized in a 0.35 μm BiCMOS process, as an active device. First, we give a brief background to SiGe HBT device physics. The key point is to initiate quantitative analysis on the influence of defects induced during extrinsic base implantation on electric performances of this device. These defects are responsible for the current fluctuations at the origin of low frequency noise in BiCMOS technologies. Next, we investigate the effect of implantation defects as a source of noise in semiconductors on the phase noise of a radiofrequency LC oscillator. We observe their influence on the oscillator phase noise, and we quantify the influence of their energy distribution in the semiconductor gap. Second, we give a behavioral model of an LC oscillator containing a SiGe HBT as an active device. The key goal is to study the susceptibility of a radiofrequency oscillator built around a SiGe HBT to phase noise disturbance sources. Based on the time variance behavior of phase noise in oscillators, transient simulations (in the time domain) were used to analyze the time-dependent noise sensitivity of the oscillator.

Origins of Low-Frequency Noise and Interface Traps in 4H-SiC MOSFETs

Detailed studies of the temperature and voltage dependences of the low-frequency noise of 4H-SiC MOSFETs and TCAD simulations show that the noise is caused primarily by interface traps. First-principle calculations identify these traps as carbon vacancy clusters and nitrogen dopant atoms at or near the SiC/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> interface.

Origin of low-frequency noise in pentacene field-effect transistors

Measurements of power spectral density (PSD) of low-frequency noise (LFN) in pentacene field-effect transistors reveal the preponderance of a 1/ f-type PSD behavior with the amplitude varying as the squared transistor gain and increasing as the inverse of the gate surface area. Such features impose an interpretation of LFN by carrier number fluctuations model involving capture/release of charges on traps uniformly distributed over the gate surface. The surface slow trap density extracted by the noise analysis is close to the surface states density deduced independently from static I(V) data, which confirms the validity of the proposed LFN interpretation. Further, we found that the trap densities in bottom-contact (BC) devices were higher than in their top-contact (TC) counterparts, in agreement with observations of a poorer crystal structure of BC devices, in the contact regions in particular. At the highest bias the noise originating from the contact resistance is also shown to be a dominant component in the PSD, and it is well explained by the noise originating from a gate-voltage dependent contact resistance. A gate area scaling was also performed, and the good scaling and the dispersion at the highest bias confirm the validity of the applied carrier number fluctuations model and the predominant contact noise at high current intensities.

Modelling of parasitic effects induced by electrically active defects in a SiGe HBT

In this paper, we present a numerical modelling of a NPN SiGe heterojunction bipolar transistor (HBT) realized in an industrial 0.35 µm BiCMOS process, using our own software simulator “SIBIDIF”, taking into account some electrically active defects in the HBT device. The electric performances of this device can be penalized by the presence of defects inherent to the complex structure shrinking. For our devices, most of these relevant defects are located at the vertical interface between the spacers and the polysilicon emitter, due to the Reactive Ion Etching (RIE) process step. Nevertheless, their localization, as well as theirs effective density or their capture section, have an influence on the electric characteristics of the HBT's. As a check, we find some good agreement between our simulated results and some experimental ones. Our work is focused on the identification of defects responsible for the current fluctuations at the origin of low frequency noise or Random Telegraphic Signals in industrial submicronic BiCMOS technologies. Gummel characteristics are simulated in order to identify generation-recombination or trap assisted tunnelling process in the base current. We have shown that devices having an excess base current present random discrete fluctuations on the base current.

On the Origin of the Excess Low-Frequency Noise in Graded-Channel Silicon-on-Insulator nMOSFETs

The origin of the low-frequency noise in graded- channel silicon-on-insulator nMOSFET is studied as a function of the back-gate bias at a low drain-to-source bias. It is shown that an excess noise peak that is correlated with the peak in the transconductance can be observed. This excess noise is due to a generation-recombination component in the low-frequency range, which is suppressed when the back gate is in accumulation mode.

Time Domain and Frequency Analysis of Random Telegraph Signal and the Contributions of G-R Centres to I-V Instabilities in 4H-SiC MESFETs

Our work is focused on the identification of defects responsible for current fluctuations at the origin of low frequency noise or random telegraphic signals in 4H-SiC MESFETs on semiinsulating (SI) substrates. We show that devices having instabilities have DC output characteristics with random discrete fluctuations of the drain current. The RTS noise parameters analysis (amplitude, high and low state time durations) as a function of temperature and bias voltage provides the signature of the involved traps (activation energy and cross section both for emission and capture). From the power spectral density of the drain current noise (PSD) we have measured the cut-off frequency of a single trap even at very low frequencies (from 0.1 Hz) and we propose that the noise responsible of RTS fluctuations is a generation-recombination noise. Finally, it is shown that the frequency analysis of the random telegraphic signal is a well-suited tool for the study of single defects in very small devices.

Impact of Post-Oxidation Annealing on Low-Frequency Noise, Threshold Voltage, and Subthreshold Swing of p-Channel MOSFETs

The impact of post-oxidation annealing on the low-frequency noise, threshold voltage, and subthreshold swing of p-channel MOSFET is reported. The low-frequency noise is improved significantly with post-oxidation annealing and a modest V/sub T/ and S reduction is observed. Oxide traps are primarily extracted from measured noise. They are also extracted from threshold voltage and subthreshold slope shift. The contribution of oxide traps to threshold voltage shift and 1/f noise is analyzed through quantitative approach in the light of correlated fluctuation theory. Analysis on experimental results shed light on the well-known controversy about the origin of low-frequency noise, suggesting that experimental results are in agreement with mobility fluctuation theory whereas correlated number fluctuation theory explains the result assuming only a fraction of total oxide charge at a given energy level participates in the generation of low-frequency noise.

Origin of low frequency noise in polycrystalline silicon thin-film transistors

The low frequency noise in polycrystalline silicon thin-film transistors (TFTs) has its origin in both sources: (i) the Si/SiO 2 interface; and (ii) the grain boundaries present within the transistor channel. A model is developed which takes into account the fluctuations of carriers in both sources of noise. Noise is measured in two types of TFTs. In one type, the poly-Si layer has a low in-grain defect density (5×10 8 cm −2) and an average grain size of the order of 100 nm. In the other type of device the average grain size is of the order of 2500 nm while the in-grain defects density varies from 5×10 10 cm −2 to 5×10 12 cm −2. The noise analysis shows that for the first type, the Si/SiO 2 dominates while for the second type of device, the two sources of noise are present. The model also gives an estimation of the electronic parameters of the device.

Origin of low-frequency noise in polycrystalline silicon thin-film transistors

Low-frequency drain current fluctuation noise was measured in a series of polycrystalline silicon thin-film transistors (polysilicon TFTs), characterized by an average grain size Lg and in-grain defect density Din. In one type of polysilicon TFT, Din is low (about 5×108 cm−2) and Lg varies from about 67 to 145 nm. In another type of polysilicon TFT, Lg remains constant (about 2.5 μm) and Din varies from about 5×1012 to 5×1010 cm−2. It is demonstrated that the noise originates from fluctuations of carriers due to carrier capture/release processes: (a) in traps located near the polysilicon/SiO2 interface and (b) in traps located at the grain boundaries. The polysilicon/SiO2 interface is distinguished from that of the crystalline silicon/SiO2 by comprising the in-grain traps, in addition to the oxide traps. The proposed carrier number fluctuation model, sufficient to explain noise in polysilicon TFTs, is closely related to the structural parameters Lg and Din of the polysilicon layer.

Time domain and frequency analysis of RTS noise in deep submicron SiGe HBTs

Our work is focused on the identification of defects responsible for the current fluctuations at the origin of low-frequency noise or random telegraphic signals in industrial 0.35 μm BiCMOS technologies. Gummel plots are modelled in order to identify generation–recombination or trap-assisted tunnelling process in the base current. We show that devices having excess base current present random discrete fluctuations on the base current. The analysis of the RTS noise parameters (amplitude, high and low state time durations) as a function of temperature and bias voltage allow us to characterize the traps involved. The conventional technique consists of a statistical treatment of the RTS time domain data. The single trap capture cross-sections and activation energy are deduced with an Arrhenius plot. In order to improve the RTS analysis, we have developed an FFT-based method. The technique allows us to calculate the noise spectrum and to measure the cut-off frequency of a single trap even at very low frequencies (from 0.1 Hz). Finally, it is shown that the frequency analysis of the random telegraphic signals is a well-suited tool for the study of single defects in very small devices. Furthermore, it is complementary with conventional LFN measurements and extended to the very-low-frequency range.

On the origin of low frequency noise in GaAs metal–semiconductor field-effect transistors

The origin of low frequency (LF) noise of GaAs metal–semiconductor field-effect transistors (MESFETs) was examined. A few generation-recombination components dominate the flicker noise present in the measured spectral noise intensity. It follows that the noise scales proportionally to L−3 (L stands for channel length). The earlier is obeyed perfectly when the noise originated in the channel access areas is negligible compared to the LF noise of the region underneath the gate. Next, it was observed that the corner frequency of the Lorentzian noise components depends on the gate-to-source bias and does not depend on the device geometry. The third important observation is that the LF noise power does not depend on the source-to-gate bias at frequencies higher than 100 Hz. It was shown that both fluctuations of the mobility and fluctuations in the carrier density inside the channel could not explain the observed noise. We claim that charge fluctuations in the Shockley–Read–Hall centers found inside the depleted layer below the gate electrode are likely to be the origin of low frequency noise in GaAs MESFETs.

Origin of low frequency noise and 1/f fluctuations of tunneling current in scanning tunneling microscopes

The generation mechanism of conspicuous low frequency noise (including 1/f fluctuations) observed in the tunneling current of scanning tunneling microscopes was studied experimentally by investigating combinations of Pt–Ir tips and Au films or crystalline graphite samples. For 1/f noise, the noise intensity at a fixed current increases with increasing bias voltage or increasing tip–sample distance z. The noise power varies from place to place in a sample surface of Au film. The spatial variation of the noise has a positive correlation with the magnitude of the tunneling barrier height φ measured by the z modulation method. The demodulated signal in the z modulation experiments also exhibits fluctuations with a 1/f spectrum of the relative magnitude nearly equal to that in the current noise. The above features are observed also in high vacuum (10−7 Pa), ruling out the possibility that the current noise is brought about by absorption/desorption of gas molecules in the ambient. Tips capable of imaging graphite surface in atomic resolution sometimes yield random telegraphic noise with a Lorentzian spectrum, which is well understood by considering that the sharp tips select a single relaxation process that happens to be located in the narrow current path. Nevertheless, the 1/f spectra were in many cases obtained even in the atomic-resolvable tips. The experimental results are discussed based on two models, the φ fluctuation model and the phonon density fluctuation model.

Spectral and random telegraph noise characterizations of low-frequency fluctuations in GaAs/Al/sub 0.4/Ga/sub 0.6/As resonant tunneling diodes

The origin of low-frequency noise in resonant-tunneling diodes is investigated through spectral and time-domain characterizations over a wide range of temperatures and biasing conditions. The experiments were conducted on devices fabricated on GaAs/Al/sub 0.4/Ga/sub 0.6/As material system. Detailed analyses on the temperature and bias dependences of the random telegraph noise and Lorentzian structures in the noise power spectral densities showed that the low-frequency excess noise arises from hopping conduction of electrons from the emitter to the quasi-bound states in the quantum well. The capture of an electron by a trap in the energy barrier causes fluctuations in the transmission coefficient of the electron due to the modulation of the barrier potential.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

On the origin of low frequency noise in HTCS thin films

Pronounced low frequency voltage noise extending into MHz frequencies was observed in current biased granular Y-Ba-Cu-O films. At some particular bias conditions it was possible to isolate the random telegraph voltage noise produced by a single elementary two-level fluctuator. The telegraph signal and the power spectrum of the noise depended strongly on the dc bias current and on the applied magnetic field. On the basis of experimental observations two alternative mechanisms; charge carrier trapping in the barriers of intrinsic Josephson junctions and magnetic flux jumping, auto-detected by intrinsic dc SQUIDS, are proposed as possible sources of the 1/f noise in superconducting high- T c films.