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With the continuous warming of the global climate, expanding the use of renewable energy has become one of the main social responsibilities. However, as the number of installed wind turbines and their physical dimensions continue to increase, the issue of generated noise has become increasingly significant in influencing the acceptance and endorsement of wind power projects by neighboring communities. In this paper, we investigated the noise generated by two wind turbine units with rated powers of 1.5 MW and 4.5 MW and analyzed the variations in low-frequency noise during their operation and shutdown periods. This research shows that the power of a single unit has a significant impact on the low-frequency noise emitted into the environment. Compared with 1.5 MW wind turbines, 4.5 MW wind turbines generate more low-frequency noise when operating at the same wind speed. Further analysis of the narrowband frequency spectra and one-third octave spectra of the measured noise indicates that the low-frequency noise from the 4.5 MW wind turbine increases significantly in the range of approximately 80 Hz to 300 Hz, with more pronounced variations below 250 Hz corresponding to changes in wind speed. However, the overall variations in low-frequency noise with wind speed are not as notable as those observed for the 1.5 MW wind turbine. Due to the relatively weak attenuation of low-frequency noise in the atmosphere, the higher low-frequency content of large wind turbines may cause more distress to residents near wind farms. The result of this study emphasizes that in the planning and design of wind power projects, in addition to considering the efficiency of single-unit power generation and the contribution of renewable energy, it is also necessary to pay full attention to noise emission issues to ensure that the project is widely supported and accepted in the community. [ABSTRACT FROM AUTHOR]

Low-frequency noise modeling and estimation is a critical issue in the design of analog and digital circuits, especially for short-channel CMOS technologies. The conventional noise models do not fit the experimental results adequately at frequencies close to DC for amplifiers and close to the carrier frequency for oscillators. Furthermore, measuring this noise necessitates the use of specialized and expensive equipment. In this paper, the bound of carrier trapping and releasing are extracted while examining the characteristics of low-frequency noise using the EMD method, and an innovative model based on carrier number fluctuations is proposed. The method introduces a low-cost measurement system for low-frequency noise. The performance accuracy of this measurement system and the proposed model is evaluated and compared with conventional noise modeling methods. The evaluation results demonstrate the success of the proposed measurement setup and model in estimating near-DC noise.

This paper presents the design and testing of an ultra-low-noise transimpedance amplifier (TIA) for low-frequency noise measurements on low-impedance (below 1 kΩ) devices, such as advanced IR photodetectors. When dealing with low-impedance devices, the main source of background noise in transimpedance amplifiers comes from the equivalent input voltage noise of the operational amplifier, which is used in a shunt–shunt configuration to obtain a transimpedance stage. In our design, we employ a hybrid operational amplifier in which an input front end based on ultra-low-noise discrete JFET devices is used to minimize this noise contribution. When using IF3602 JFETs for the input stage, the equivalent voltage noise of the hybrid operational amplifier can be as low as 4 nV/√Hz, 2 nV/√Hz, and 0.9 nV/√Hz at 1 Hz, 10 Hz, and 1 kHz, respectively. When testing the current noise of an ideal 1 kΩ resistor, these values correspond to a current noise contribution of the same order as or below that of the thermal noise of the resistor. Therefore, in cases in which the current flicker noise is dominant, i.e., much higher than the thermal noise, the noise contribution from the transimpedance amplifier can be neglected in most cases of interest. Test measurements on advanced low-impedance photodetectors are also reported to demonstrate the effectiveness of our proposed approach for directly measuring low-frequency current noise in biased low-impedance electronic devices. [ABSTRACT FROM AUTHOR]

Low-frequency noise modeling and estimation is a critical issue in the design of analog and digital circuits, especially for short-channel CMOS technologies. The conventional noise models do not fit the experimental results adequately at frequencies close to DC for amplifiers and close to the carrier frequency for oscillators. Furthermore, measuring this noise necessitates the use of specialized and expensive equipment. In this paper, the bound of carrier trapping and releasing are extracted while examining the characteristics of low-frequency noise using the EMD method, and an innovative model based on carrier number fluctuations is proposed. The method introduces a low-cost measurement system for low=frequency noise. The performance accuracy of this measurement system and the proposed model is evaluated and compared with conventional noise modeling methods. The evaluation results demonstrate the success of the proposed measurement setup and model in estimating near-DC noise. [ABSTRACT FROM AUTHOR]

In this work, we analyze a resistive switching random access memory (RRAM) device with the metal–insulator–metal structure of Al/αTiOx/Al. The transport mechanism of our RRAM device is trap-controlled space-charge limited conduction, which does not change during the endurance test. As the number of resistive switching (RS) cycles increases, the current in the low-resistance state (LRS) does not change significantly. In contrast, degradation in the high-resistance state (HRS) is noticeably evident. According to the RS cycle, the current shift fits well with the stretched-exponential equation. The normalized noise power spectral density (Si/I2) measured in the HRS is an order of magnitude higher than that in the LRS owing to the difference in the degree of trap occupancy, which is responsible for the transition of resistance states. During the consecutive RS, the Si/I2 in the HRS rapidly decreases for approximately 100 cycles and then saturates. In contrast, in the LRS, the Si/I2 does not change significantly. Here we propose a model associated with the endurance degradation of the experimental device, and the model is verified with a 1 / f noise measurement. [ABSTRACT FROM AUTHOR]

Low-frequency noise (LFN), or 1/ ${f}$ -noise, can be used effectively to evaluate device reliability which is a major concern in analog as well as digital circuits. In this work, we present 1/ ${f}$ -noise characterization of vertical InAs/InGaAs gate-all-around (GAA) MOSFETs with a 70-nm gate length (${L}_{G}$) measured at cryogenic temperatures down to 15 K. The measurements at cryogenic temperatures reveal that the physical mechanism of 1/ ${f}$ -noise changes from carrier number fluctuations at 300 K to mobility fluctuations at 15 K. We conclude that the channel conduction at 15 K is dominated by the nanowire core instead of the nanowire surface due to the effect of the border and interface traps freezing out. Vertical InAs/InGaAs GAA MOSFETs at 15 K, due to reduced surface scattering, exhibit a low value of Hooge parameter, $\alpha _{\text {H}} $ ~ $5\times 10^{\text {-{6}}}$ and also have a low input-referred gate voltage noise spectral density, ${S}_{\text {VG}} = 4.3\,\,\mu \text{V}^{{2}}\,\,\mu \text{m}^{{2}}$ Hz $^{\text {-1}}$ that are important for reliable cryogenic circuit applications. [ABSTRACT FROM AUTHOR]

Low-frequency noise measurements are carried out to investigate optoelectronic characteristics of CdSe quantum dot (QD)/indium-gallium-zinc-oxide (IGZO) heterostructured hybrid phototransistor with respect to various QD surface ligands, such as chalcometallate ligands (Sn2 $\text{S}_{6}^{4-}$ and Sn2Se $_{6}^{4-}$) and thiocyanate (SCN $^{-}$). It is found that Sn2 $\text{S}_{6}^{4-}$ and Sn2Se $_{6}^{4-}$ -capped QD/IGZO phototransistors show enhanced optoelectronic characteristics such as responsivity (${R}$) of $3.06\times 10$ 3 A W−1 and $8.8\times 10$ 2 A W−1, respectively, and photodetectivity (${D}^\ast$) of $2.1\times 10$ 13 Jones and $6.18\times 10$ 11 Jones, respectively, compared with SCN $^{-}$ -capped CdSe QD/IGZO phototransistors (${R}$ of $1.21\times 10$ 3 A W−1 and ${D}^\ast $ of $2.02\times 10$ 11 Jones). Independently, all these devices exhibit 1/ ${f}$ low-frequency noise dependence in the subthreshold, ohmic, and saturation regimes. In particular, in the ohmic and saturation regime, the low-frequency noise properties follow the bulk mobility fluctuation mechanism for the chalcometallate ligands-based devices, while carrier number fluctuation model is dominant for the SCN $^{-}$ -based devices. Thus, low-frequency noise analysis may provide meaningful information to evaluate important parameters for nanomaterial-based optoelectronics. [ABSTRACT FROM AUTHOR]

We investigate the effects of length (${L}$) and width (${W}$) scaling on the low-frequency noise characteristics of the ferroelectric tunnel junction (FTJ). The FTJ is composed of metal/ferroelectric/dielectric/semicondu- ctor (TiN/HfZrO2/SiO2/ ${n}^{+}$ Si). In the high-resistance state, 1/ ${f}$ noise increases proportionally to 1/ ${W}^{\alpha }{L}^{\beta }$ ($\alpha \cong ~1$ , $\beta >1$), whereas the shot noise has no scaling dependence. In the low-resistance state, the 1/ ${f}$ noise of the FTJ shows a more sensitive dependence on ${L}$ scaling than ${W}$ scaling since the switching and conduction mechanisms are more affected by the process-induced damaged edge regions. [ABSTRACT FROM AUTHOR]

Desert seismic data have the characteristics of low signal-to-noise ratio (SNR) and low-frequency, which pose a major challenge to noise attenuation. In this letter, we propose a denoising method for desert seismic data that combines the Gaussian conditional random field (GCRF) and the sparsity measurement. The sparsity measurement method is designed to replace the noise sampling method in the posterior frame. To calculate the block sparsity, first the seismic data blocks are divided into three groups: high sparsity blocks, medium sparsity blocks, and low sparsity blocks. Then different denoising parameters are determined according to the sparsity of seismic signal and the nonsparsity of desert low-frequency noise. Consequently, this targeted parameter setting achieves a more thorough suppression of noise and less attenuation of seismic signals. Both the synthetic and real data experiments prove the effectiveness of the method in this letter. [ABSTRACT FROM AUTHOR]

Light field (LF) imaging sensors based on micro-lens array are susceptible to numerous noise pollution when collecting raw 4D LF data due to their own special structural design, which affects visual perception and subsequent applications such as depth estimation. Unfortunately, existing 2D image denoising methods are difficult to directly apply to 4D LF images. To this end, this paper proposes a new LF denoising method based on spatial-angular collaborative encoding network, considering the inherent 4D structure of LF image. Specifically, the convolutions in the spatial and angular branches are first constructed to extract specific 2D spatial and 2D angular features from noisy LF data. Then, a tailored spatial-angular collaborative encoder is designed to co-process spatial-angular features and improve the expression ability of features. After that, the spatial-angular feature fusion module is constructed to fuse the extracted features. Finally, the denoised LF image is reconstructed by a residual prediction module integrating attention mechanism. In particular, the proposed method simultaneously reconstructs all sub-aperture images of LF in one forward inference, so as to preserve the angular consistency of the denoised LF image. Extensive experimental results show that the proposed method outperforms the state-of-the-art methods in both subjective visual perception and objective quality evaluation. Furthermore, the proposed method preserves the parallax structure well, which is beneficial for subsequent LF applications. [ABSTRACT FROM AUTHOR]

Low-frequency noise characteristics of ZnO nanowire field-effect transistors (FETs) are presented at temperatures down to 10 K. The carrier number fluctuation (CNF) model and Hooge’s model are used to analyze the low-frequency noise in the studied devices. From 293 down to 200 K, the normalized noise power spectrum density (PSD) is proportional to (gm/Id)2 due to CNF caused by the trapping and detrapping process between the channel carriers and oxide traps near the semiconductor and the dielectrics interface. In this case, the low-frequency noise is induced by flat-band voltage fluctuation. The density of the traps in the gate dielectrics near the Fermi level ranges from 9.4 × 1010 to 3.8 × 1010 cm−2 eV−1 from 293 and 200 K. At lower temperatures, from 150 down to 100 K, the noise mechanism is mobility fluctuation, attributed to electron and space-charge scattering due to the hoping process and slow motions of electrons. The extracted Hooge’s parameter in this temperature ranges in the order of 10−3 to 10−2. In the temperature range from 30 down to 10 K, the low-frequency noise is dominated by both CNF and mobility fluctuation caused by Coulomb scattering between oxide traps and electrons. [ABSTRACT FROM AUTHOR]

Low-frequency noise is a critical characteristic of transistors, but there are only a few experimental works on the noise in printed electronics. In this work, we characterize the low-frequency noise of inkjet-printed electrolyte-gated thin-film transistors (EGTs) with indium-oxide semiconductors. We confirm that the carrier number fluctuation with correlated mobility fluctuation is the dominating noise generation mechanism. Also, we present the benchmark analysis on the noise level of various thin-film technologies. Notably, the extracted value of trap density near the insulator-channel interface is high, indicating an inferior quality of solution-processed and inkjet-printed thin-films. However, because of electrolyte-gating, the large areal gate capacitance compensates the negative effect of the high trap density, effectively reducing the flat-band voltage noise. As a result, the normalized drain current noise is considerably lower than solution-processed transistors and comparable with sputtered inorganic transistors with dielectric gating. This renders the electrolyte-gating approach useful in reducing the noise for printed/solution-based transistors, suitable for low-noise applications. [ABSTRACT FROM AUTHOR]

In this article, the interfacial properties of nMOSFETs with different thickness high-κ AlL2O3 capping layer on an 8-nm SiO2 and TiN gate stacks have been investigated using electrical measurement and low-frequency noise at room temperature. It is shown that the predominant 1/ƒ noise is governed by the number fluctuations mechanism. It is indicated that: 1) presence of an Al2O3 capping layer increases the noise power spectral density and, hence, the oxide trap density has an influence on the low-field mobility further and 2) effective work-function and the threshold voltage of nMOSFET should be modulated using the high-κ Al2O3capping layers. [ABSTRACT FROM AUTHOR]

Noise suppression is a crucial step before seismic data analysis. The noise in desert areas has the characteristics of nonstationary, non-Gaussian, and low-frequency, which makes some traditional methods cannot suppress the noise well. The weighted nuclear norm minimization (WNNM), one of the most effective methods to suppress noise in all low-rank matrix approximation methods, assigns different weights to different singular values. The good denoising performance of the WNNM is based on the accuracy of block matching, and the theoretical basis of block matching is the nonlocal self-similarity of clean signals. However, the noise will destroy the nonlocal self-similarity and greatly affect the accuracy of block matching. In this article, to reduce the influence of noise on block matching, we use a bandpass filter to process each noisy block before block-matching and use the similarity between the filtered blocks to represent the similarity between the original noisy blocks, then stack the most similar noisy blocks to construct a matrix for further denoising. Experimental results demonstrate the efficiency of the proposed method for low-frequency noise suppression. [ABSTRACT FROM AUTHOR]

Lots of low-frequency noise including random noise and surface waves seriously reduces the quality of desert seismic data. However, the suppression for desert low-frequency noise faces three main problems: nonstationary and non-Gaussian of random noise; strong energy of low-frequency noise; a more serious frequency-band overlap between effective signals and low-frequency noise. Robust principal component analysis (RPCA) is a classical low-rank matrix (LM) recovery method which is very suitable for processing nonlinear noise. It can decompose noisy data to the optimal LM and sparse matrix (SM), which include most effective signals and noise, respectively. Therefore, the RPCA is introduced to suppress desert low-frequency noise. However, due to the low signal-to-noise ratio (SNR) and serious frequency-band overlap, much low-frequency noise still remains in the LM of desert seismic data after the decomposition of RPCA. Meanwhile, some nonnegligible effective signals are decomposed into the SM of desert seismic data. To solve this problem, the convolutional neural network (CNN) is introduced to extract effective signals from SM and LM. By constructing suitable training sets to guide the CNN’s training, the CNN denoising models after training are used to predict the effective signals from these two matrices, respectively. In this article, to approach real desert seismic data, we use a variety of seismic wavelets to simulate different types of seismic events, and then use these synthetic seismic events and real desert low-frequency noise to construct training set. In experiments, our method can raise the SNR of synthetic noisy data from −8.69 to 9.63 dB. [ABSTRACT FROM AUTHOR]

Effects of additional thermal budget associated with a three-dimensional (3D) fabrication sequence are evaluated for the total-ionizing dose radiation response of fully depleted silicon-on-insulator (FD-SOI) MOSFETs. Current-voltage and low-frequency (1/ ${f}$) noise measurements are compared for (1) conventional planar FD-SOI MOSFETs, and (2) MOSFETs formed in the bottom layer of the 3D process and subjected to the process steps associated with formation of a second active layer. Similar radiation-induced voltage shifts and increases of 1/ ${f}$ noise are observed after irradiation for both types of structures. These similar changes in response show that the additional thermal processing involved with 3D fabrication has little effect on border-trap densities and radiation-induced charge trapping in gate and/or buried oxides of MOSFETs formed in the bottom layer of the 3D process. [ABSTRACT FROM AUTHOR]

High-quality seismic exploration data are the basis of geological exploration. However, due to the increasingly complex environment in the exploration area, the signal-to-noise ratio (SNR) of seismic data is getting lower and lower. Eliminating noise is the most direct mean to improve the SNR and quality of seismic data. The Tarim Basin with a desert surface in China is rich in energy, but due to the variability of surface conditions, the desert noise has nonstationary, nonlinear, spatial directivity, low frequency, and other characteristics, which make noise attenuation very difficult. Aiming at this problem, we develop an extension of complex diffusion filter, namely approximate-message-passing-based complex diffusion, which is used to eliminate noise in desert seismic exploration data and enhance effective signals. Compared with the traditional complex diffusion, this letter adds a noise estimate in its diffusion processing, which improves the algorithm’s ability to eliminate desert noise. The experimental results of synthetic and field seismic data show that the proposed method is more effective than other methods. Not only it can remove the noise and surface wave in the desert seismic record but also can preserve the effective signal. Therefore, we believe that the proposed method can provide a new idea for desert seismic signal processing. [ABSTRACT FROM AUTHOR]

In this study, carbon nanotube fibers (CNTFs) were strengthened by densifying and reorienting CNT bundles using a triblock copolymer (poly (propylene glycol)– block -poly (ethylene glycol)– block -poly (propylene glycol (PPG–PEG–PPG)). This copolymer possesses a unique combination of hydrophilic and hydrophobic molecules, enabling it to easily penetrate and expand the distance between bundles. Through a stretching process after impregnation, the CNTFs induced a structural alignment of the bundles, resulting in high integration of the CNT bundles. The microstructural analysis of the fiber cross-section revealed an increased number of aligned CNTs along the fiber direction, concomitant with a reduction in the bundle-to-bundle distance owing to bundle aggregation. The highly aligned structure showed an average specific tensile strength of 0.536 N/tex and specific elastic modulus of 66.3 N/tex, which is an increase of 175 % and 252 %, respectively, compared to the pristine CNTF. The polymer infiltration stretching method effectively aggregated CNT bundles and removed macro voids within the CNTF. Additionally, the densification and alignment of CNTFs were characterized through novel low-frequency noise measurement and analysis. Understanding the nanoscale structure and morphology of CNTFs in nanoscale will provide valuable guidance for building enhanced strengthening strategies. [Display omitted] • CNT fiber (CNTF) was reoriented and densified by wet stretching method using a triblock copolymer. • The structure modified CNTFs enhanced tensile strength, Young's modulus, and electrical conductivities. • A low-frequency noise method was used to investigate the densification and alignment quality of CNT bundles. [ABSTRACT FROM AUTHOR]

In this article, we report for the first time that the well-established diffusion noise can be apparently increased in large proportions and that such a situation can be very common at some specific frequencies in the p-n junction structures operating at a very low direct bias current. Noise theories and the associated measurement techniques are a major issue for the emerging semiconductor technologies, the development of accurate computer-aided design (CAD) models, and the designing of low-noise circuits and systems. The conventional shot noise model usually satisfactorily describes the p-n junction noise in solid-state devices, such as diodes and transistors. It has proven to be very efficient for many different conventional and advanced semiconductor technologies. However, alterations may sometimes be needed as previous works indicate scenarios where this so-called shot noise exhibits deviations from the theory, which translates into some noise suppression. In this article, we report on alterations that look like low-frequency diffusion noise enhancement (unexpected noise increase). It occurs at low current levels, for many generic commercially available diodes and the p-n junctions in transistors. Therefore, we propose an appropriate electrical noise model that satisfies both the low-frequency noise experimental data and the electrical behavior of the devices observed from impedance spectroscopy. We also evaluate this model as the ambient temperature is varied. Finally, it is discussed how this model can be connected to the conventional van der Ziel shot noise model and a better insight on the possible origin of such diffusion noise enhancement is provided. [ABSTRACT FROM AUTHOR]

Light field (LF) cameras provide perspective information of scenes by taking directional measurements of the focusing light rays. The raw outputs are usually dark with additive camera noise, which impedes subsequent processing and applications. We propose a novel LF denoising framework based on anisotropic parallax analysis (APA). Two convolutional neural networks are jointly designed for the task: first, the structural parallax synthesis network predicts the parallax details for the entire LF based on a set of anisotropic parallax features. These novel features can efficiently capture the high-frequency perspective components of a LF from noisy observations. Second, the view-dependent detail compensation network restores non-Lambertian variation to each LF view by involving view-specific spatial energies. Extensive experiments show that the proposed APA LF denoiser provides a much better denoising performance than state-of-the-art methods in terms of visual quality and in preservation of parallax details. [ABSTRACT FROM AUTHOR]

Electrocardiograph (ECG) denoising is the most important step in diagnosis of heart-related diseases, as the diagnosis gets influenced with noises. In this paper, a new method for ECG denoising is proposed, which incorporates empirical mode decomposition algorithm with Riegmann Liouvelle (RL) fractional integral filtering and Savitzky–Golay (SG) filtering. In the proposed method, noisy ECG signal is decomposed into its intrinsic mode functions (IMFs), from which noisy IMFs, corrupted with high-frequency (HF) and low-frequency (LF) noises, are identified by proposed noisy-IMFs identification methodologies. To denoise the signal, RL fractional integral filtering and SG filtering are applied on noisy IMFs corrupted with HF and LF noises, respectively; ECG signal is reconstructed with denoised IMFs and remaining signal dominant IMFs to obtain noise-free ECG signal. Proposed methodology is tested with MIT-BIH arrhythmia database. Its performance, in terms of signal-to-noise ratio and mean square error, is compared with other related ECG denoising methods based on fractional integral, empirical mode decomposition, and ensemble empirical mode decomposition. The obtained results by proposed method prove that the proposed method gives efficient noise removal performance. [ABSTRACT FROM AUTHOR]

We demonstrate technological improvements in phonon sector tests of the Lorentz invariance that implement quartz bulk acoustic wave oscillators. In this experiment, room temperature oscillators with state-of-the-art phase noise are continuously compared on a platform that rotates at a rate of order of a cycle per second. The discussion is focused on improvements in noise measurement techniques, data acquisition, and data processing. Preliminary results of the second generation of such tests are given, and indicate that standard model extension coefficients in the matter sector can be measured at a precision of order 10−16 GeV after taking a year’s worth of data. This is equivalent to an improvement of two orders of magnitude over the prior acoustic phonon sector experiment. [ABSTRACT FROM AUTHOR]

In this letter, an investigation of the low-frequency (LF) drain noise characteristics of the GaN/ AlGaN/GaN HEMT grown on a SiC substrate has been performed. LF drain noise measurements are performed over the frequency range of 20 Hz–1 MHz by varying chuck temperatures ( T\mathbf {\sf chuck}) between 25°C and 100°C. Furthermore, we present the 2-D TCAD physical simulation analysis of this device. TCAD simulation model has been calibrated using the measured device characteristics, and then, using the calibrated model, LF drain noise simulations have been performed. A good match is observed between drain noise measurements and simulation results, and this physically confirms that two acceptor-like traps with apparent activation energies of 0.51 and 0.57 eV, respectively, below the conduction band are located in the GaN buffer. [ABSTRACT FROM PUBLISHER]

Graphene is a very promising material for potential applications in many fields. Since manufacturing technologies of graphene are still at the developing stage, low-frequency noise measurements as a tool for evaluating their quality is proposed. In this work, noise properties of polymer thick-film resistors with graphene nano-platelets as a functional phase are reported. The measurements were carried out in room temperature. 1/f noise caused by resistance fluctuations has been found to be the main component in the specimens. The parameter values describing noise intensity of the polymer thick-film specimens have been calculated and compared with the values obtained for other thick-film resistors and layers used in microelectronics. The studied polymer thick-film specimens exhibit rather poor noise properties, especially for the layers with a low content of the functional phase. [ABSTRACT FROM AUTHOR]

We present a detailed analysis of low-frequency noise (LFN) measurements in vertical III–V nanowire tunnel field-effect transistors (TFETs), which help to understand the limiting factors of TFET operation. A comparison with LFN in vertical metal-oxide semiconductor field-effect transistors with the same channel material and gate oxide shows that the LFN in these TFETs is dominated by the gate oxide properties, which allowed us to optimize the TFET tunnel junction without deteriorating the noise performance. By carefully selecting the TFET heterostructure materials, we reduced the inverse subthreshold slope well below 60 mV/decade for a constant LFN level. [ABSTRACT FROM AUTHOR]

One regularity condition for the classical Cramér–Rao lower bound (CRLB) of an unbiased estimator to hold—that the support of the likelihood function (LF) should be independent of the parameter to be estimated—has recently been relaxed to the case of parameter-dependent support as long as the LF is continuous at the boundary of its support. For the case where the LF is not continuous on the boundary of its support, a new modified CRLB—designated the Cramér–Rao–Leibniz lower bound (CRLLB) as it relies on the Leibniz integral rule—has also been presented for the scalar parameter case. The present work derives the multidimensional CRLLB for the case of LF with parameter-dependent support by applying the general Leibniz integral rule to complete the framework of the CRLLB. [ABSTRACT FROM PUBLISHER]

Mobile measuring equipment adapted for measurements of low-frequency noise of vacuum tubes with a broad range of impedance characteristics has been developed. Control software making it possible to measure and process the obtained results in automatic mode has been created. The capability of determining the diagnostic parameters of thermionic cathodes of vacuum tubes is shown. [ABSTRACT FROM AUTHOR]

In this letter, traps-related dispersion phenomenon of GaN/AlGaN/GaN high electron mobility transistor grown on the SiC substrate is investigated through low-frequency noisemeasurements. Low-frequency drain noise measurements are performed over the frequency range of 20 Hz–1MHz and for varying chuck temperatures ( T\text {chuck}) ranging between 25 °C and 125 °C. This letter demonstrates that two prominent deep levels are present in the device-under-testwith apparent activation energies ( Ea) of 0.51 and 0.57 eV, respectively. Moreover, signatures of deep level with Ea of 0.57 eV become visible only at higher operating temperatures, due to the fact that traps dispersion occurs at very low frequencies, which is confirmed through TCAD physical simulations. [ABSTRACT FROM AUTHOR]

Planar platinum silicide (PtSi) Schottky barrier (SB) p-channel silicon-on-insulator (SOI) ion-sensitive field effect transistors (ISFETs) have been fabricated at low temperature (400 °C) for biosensor applications. The use of PtSi not only eliminates the ion implantation process and associated high temperature annealing, it also simplifies the process complexity. Both dc and low frequency noise have been characterized. It is found that the SB p-channel SOI ISFET shows a high sensitivity of 55 mV/pH and a resolution limit of 0.0136% of a pH shift with 1 Hz bandwidth. All these suggest that the low temperature PtSi SB SOI ISFET is one of the promising candidates for biochemical detection. [ABSTRACT FROM AUTHOR]

To explain the current dependences of the mean-square value of low-frequency (LF) noise current in green InGaN light emitting diodes (LEDs), a double stage low-frequency noise equivalent circuit of the LED is proposed. It is shown that the nonmonotonic dependence of the LF noise on the injection current in the LED can be explained by the effect of two LF noise generators: a noise current generator, which is localized near the heterojunction and is determined by tunnel-recombination processes at the interface, and a generator determined by recombination processes in the active region of the structure. [ABSTRACT FROM AUTHOR]

Low-frequency noise (LFN) measurements are largely used for interface quality characterization in MOSFETs. In this work, a detailed investigation of LFN technique applied to pseudo-MOSFETs in bare silicon-on-insulator (SOI) substrates is provided. A physical model capable to describe the experimental results is proposed and validated using different die areas and inter-probe distances. The effective silicon area contributing to the noise signal, the impact of defects induced by probes and the possibility to extract interface trap density are addressed. [ABSTRACT FROM AUTHOR]

In this paper, we present extensive characterization of low-frequency noise in advanced silicon germanium heterojunction bipolar transistors. We demonstrate the extraction methodology of base and collector noise spectral densities for a wide range of transistor geometries. In addition to 1/ $f$ noise, generation–recombination (G–R) mechanisms are observed at low bias in the base current noise. Their existence is confirmed by Random Telegraph Signal (RTS) noise measurements. 1/ $f$ and G–R components are extracted from the base current noise spectra and their bias dependencies are studied. Finally, base current noise spectral densities measured at the same base current density in different geometries are compared to study the individual contribution of 1/ $f$ noise from the periphery as well as the intrinsic device. Part II of this paper will discuss the modeling aspects and noise correlation. [ABSTRACT FROM AUTHOR]

In this paper, an analytical noise calculation is presented to derive the impact of process and design parameters on 1/f and thermal noise for a low-noise CMOS image sensor (CIS) readout chain. It is shown that dramatic noise reduction is obtained by using a thin-oxide transistor as the source follower of a typical 4T pixel. This approach is confirmed by a test chip designed in a 180-nm CIS process and embedding small arrays of the proposed new pixels together with state-of-the-art 4T pixels for comparison. The new pixels feature a pitch of 7.5 \mu \text{m} and a fill factor of 66%. A 0.4e- rms input-referred noise and a 185- \mu \text{V}$ /e- conversion gain are obtained. Compared with state-of-the-art pixels, also present onto the test chip, the rms noise is divided by more than 2 and the conversion gain is multiplied by 2.2. [ABSTRACT FROM AUTHOR]

Low-frequency noise measurements were performed on n-channel MOSFETs with a novel ultra-low 0.3-nm equivalent-oxide-thickness (EOT) interfacial layer (TmSiO) and two different bulk high- k dielectrics (Tm2O3 and HfO2). The MOSFETs were fabricated in a gate-last process and the total gate-stack EOT was 1.2 and 0.65 nm for the Tm2O3 and HfO2 samples, respectively. In general, both gate-stacks resulted in 1/ f type of noise spectra and noise levels comparable with the conventional SiO2/HfO2 devices with similar EOTs. The extracted average effective oxide trap density was 2.5\times 10^17 and 1.5\times 10^17 cm ^\mathrm -3 eV ^\mathrm -1 for TmSiO/HfO2 and TmSiO/Tm2O3, respectively. Therefore, the best noise performance was observed for the gate-stack with Tm2O3 bulk high- $k$ layer and we suggest that the interface free single-layer atomic layer deposition (ALD) fabrication scheme could explain this. [ABSTRACT FROM AUTHOR]

The modeling and characterization of low-frequency noise and noise variability in various regimes of operation are investigated for the main advanced complementary metal-oxide semiconductor (CMOS) technologies. Novel materials and innovative device architectures from 0.5 μm to 20 nm gate lengths are studied. The impact of gate stack, realized with ultrathin oxides, polysilicon gate and high-k/metal gate is analyzed. The influence of alternative channel materials, in particular ultrathin body silicon-on-insulator layers, strain Si and III-V materials is addressed. The comparison of low-frequency noise in advanced device architectures, including bulk Si, fully depleted SOI, FinFET, junctionless, and multi-gates structures, is shown. Accurate noise models, taking into account the main physical mechanisms, are proposed for all these very advanced technologies, which will be needed for the nanoelectronics of the next decade. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Low-frequency noise (LFN) in double-gate (DG) In–Ga–Zn–O (IGZO) thin-film transistors (TFTs) is studied to investigate the origin of performance improvement. We found that thinning down the IGZO film enhances such improvements. With 7-nm IGZO, the mobility is raised by a factor of 3.77, and the subthreshold slope is reduced to 0.17 V/decade from single-gate to DG mode. Device simulations show that bulk transport inside IGZO film emerges as the two gates field effects get coupled. The LFN results reveal a transport transition from surface to bulk and disclose the superior bulk transport that experiences slight phonon scattering with a small Hooge parameter \alpha H = 4.44 \times 10^{\mathrm {-3}} , whereas the surface transport undergoes serious charge trapping with surface trap densities about 2 \times 10^11 eV ^-1 cm ^-2 . [ABSTRACT FROM PUBLISHER]

This paper reviews and compares predictions of the Dutta-Horn model of low-frequency excess (\bf 1/\mbif) noise with experimental results for thin metal films, MOS transistors, and GaN/AlGaN high-electron mobility transistors (HEMTs). For metal films, mobility fluctuations associated with carrier-defect scattering lead to \bf 1/\mbif noise. In contrast, for most semiconductor devices, the noise usually results from fluctuations in the number of carriers due to charge exchange between the channel and defects, usually at or near a critical semiconductor/insulator interface. The Dutta-Horn model describes the noise with high precision in most cases. Insight into the physical mechanisms that lead to noise in microelectronic materials and devices has been obtained via total-ionizing-dose irradiation and/or thermal annealing, as illustrated with several examples. With the assistance of the Dutta-Horn model, measurements of the noise magnitude and temperature and/or voltage dependence of the noise enable estimates of the energy distributions of defects that lead to \bf 1/\mbif noise. The microstructure of several defects and/or impurities that cause noise in MOS devices (primarily O vacancies) and GaN/AlGaN HEMTs (e.g., hydrogenated impurity centers, N vacancies, and/or Fe centers) have been identified via experiments and density functional theory calculations. [ABSTRACT FROM AUTHOR]

The gate-stack quality of planar MOSFETs fabricated in Ge-on-Si substrates and passivated by a GeOx interfacial layer is evaluated by low-frequency noise analysis. It is shown that for both n- and p-channel transistors predominantly 1/ f^\gamma noise ( $\gamma \sim 1$ ) has been observed, which originates from number and correlated mobility fluctuations. The oxide trap density and mobility scattering coefficient derived from the input-referred voltage noise power spectral density are demonstrated to be significantly higher for nMOSFETs than for pMOSFETs with the same gate-stack, which explains the low electron mobility. [ABSTRACT FROM PUBLISHER]

Noise measurements have been carried out in the LISA bandwidth (0.1–100 mHz) to characterize an all-optical atomic magnetometer based on nonlinear magneto-optical rotation. This was done in order to assess if the technology can be used for space missions with demanding low-frequency requirements like the LISA concept. Magnetometry for low-frequency applications is usually limited by 1/ f noise and thermal drifts, which become the dominant contributions at sub-millihertz frequencies. Magnetic field measurements with atomic magnetometers are not immune to low-frequency fluctuations and significant excess noise may arise due to external elements, such as temperature fluctuations or intrinsic noise in the electronics. In addition, low-frequency drifts in the applied magnetic field have been identified in order to distinguish their noise contribution from that of the sensor. We have found the technology suitable for LISA in terms of sensitivity, although further work must be done to characterize the low-frequency noise in a miniaturized setup suitable for space missions. [ABSTRACT FROM AUTHOR]

We employed a cross correlation method to study current noise in phosphorescent organic light-emitting diodes. The noise spectra revealed two frequency-dependent components. The first component displays \({1/f}^{1.3}\) dependence and correlates with the light emission of the devices. The second component is dominant in low-bias regime and varies as \({1/f}^{2.8}\) . It is attributed to inhomogeneities of the barrier height at metal/organic interface. The extended bandwidth of the method allowed us to resolve frequency-independent term in the noise power, which was dominated by the shot noise. At bias voltages from 2.4 to 2.5 V, the Fano factor characterizing shot noise is close to one, confirming that the electron transport in this regime is limited by the carrier injection across metal/organic interface. At higher biases, in the regime where the transport is bulk-limited, the Fano factors drops to 0.5. Possible physical reasons for such behavior are discussed. [ABSTRACT FROM PUBLISHER]

In this paper we discuss the regularity conditions required for the classical Cram?er-Rao lower bound (CRLB) for real-valued (nonrandom unknown) parameters to hold. It is shown that the commonly assumed requirement that the support of the likelihood function (LF) should be independent of the parameter to be estimated can be replaced by the much weaker requirement that the LF is continuous at the end points of its support. Parameter-dependent support of the LF arises when an unknown parameter is observed in the presence of additive measurement noise and the measurement noise probability density function (pdf) has a finite support. It is also pointed out that the commonly cited requirements of absolute integrability of the derivatives of the LF should be replaced by requirements on the log-LF (LLF). Some practical examples of finite-support measurement noises, which lead to parameter-dependent LF support, are discussed in light of the above. For the case where the LF is not continuous at the end points of its support, a new modified CRLB ?designated as the Cram?er-Rao-Leibniz lower bound (CRLLB), since it relies on Leibniz integral rule ? is presented and its use illustrated. The CRLLB is shown to provide valid bounds for a number of long-standing problems for which the CRLB was shown in the literature as not valid, in particular, for a uniformly distributed measurement noise. [ABSTRACT FROM AUTHOR]

For a number of decades, the modeling of microwave transistors relied on specific well-known characterization methods. Those methods include S-parameters measurement through vector network analyzers (VNAs) ranging from the lower end of the RF spectrum to the millimeter-wave (mm-wave) region and load pull measurements of transistors used for the design of power amplifiers (PAs). Later, the availability of more powerful computer-aided design (CAD) software enabled the need for models of active microwave devices, thus driving a huge amount of research activity on microwave transistor modeling. Simultaneously, new transistor technologies were invented, combining working concepts such as heterojunction bipolar transistors (HBTs), metal semiconductor field effect transistors (MESFETs) or high electron mobility transistors (HEMTs) and new materials such as gallium arsenide (GaAs), gallium nitride (GaN), indium phosphide (InP), and silicon germanium (SiGe), to cite only the main ones. [ABSTRACT FROM PUBLISHER]

A ballistic-electron transport-based semiconductor nanorectifier, also known as a ballistic rectifier, has been demonstrated to have an intrinsic zero threshold voltage. In this paper, we characterize its low-frequency noise properties and show that the zero-threshold property enables elimination of the flicker noise. As a potential terahertz detector, the ballistic rectifier exhibits a noise equivalent power in the range of commercially available, uncooled thermal terahertz detectors. The observed noise in the device at finite biases is modeled quantitatively. The derived simple formula reveals that the narrowest part of the electron channels has a dominant role in the device noise properties. [ABSTRACT FROM PUBLISHER]

• Experimental observation and investigation of parasitic oscillation in solar cells. • Identification of oscillation's origin as the result of device/amplifier coupling. • Suggestion of two possible solutions for LFN characterization of solar cells with no parasitic oscillations. The analysis of low-frequency noise in solar cells is a very useful tool for defect characterization or understanding of fluctuation mechanisms in photodiodes. This type of noise characterization can however be limited by the presence of an undesired peak in the frequency spectra, caused by an oscillation in the measured current. It is shown in this work that this phenomenon originates in the interaction between the noise measurement system and the test structures of the solar cells, which usually introduce a high parasitic capacitance. Through experimental measurements, the link between the center frequency of the peak and the sensitivity of the noise measurement amplifier, as well as the solar cell surface area were explored. Finally, it is shown that, for characterization purposes, the oscillation peak could be pushed to higher frequencies by measuring smaller area cells or attenuated by choosing electrode shapes that enhance the device series resistance. [ABSTRACT FROM AUTHOR]

• Provided an extensive data set of in-cabin noise measurements in six different aircraft models while in operation. • The noise measurement has been performed in medium-haul and long-haul flights. • The sound pressure levels of in-cabin noise have been measured on two different decibel scales, namely, A-weighted [dB(A)] and C-weighted scales [dB(C)]. • The results confirmed the quietest aircraft, as claimed by some published reports. The aviation industry has seen dramatic growth over the decades till the recent disruption due to the COVID-19 pandemic. Moreover, long-haul routes with a distance of more than 4000 km are common for major airlines worldwide. Therefore, aircraft cabin noise assessment is essential, especially in long-haul flights, for passenger and flight crew health wellness. In this paper, the cabin noise of five wide-body aircraft, namely Airbus A330-300ER, A350-900, A380–800, and Boeing B777-200ER and B787-900, was recorded using a calibrated in-house developed smartphone application. The sound pressure levels of in-cabin noise have been measured on two different decibel scales, namely, A-weighted [dB(A)] and C-weighted scales [dB(C)]. The sound pressure levels of Airbus A380–800 were lowest among selected models, while the in-cabin pressure level values of Airbus A350-900 were maximum. However, the difference in decibel levels between the aircraft is minimal as it is within 3 dB. [ABSTRACT FROM AUTHOR]

Total-ionizing-dose (TID) mechanisms are evaluated in 16 nm Si bulk FinFETs at doses up to 1 Grad(SiO 2) for applications in high-energy physics experiments. The TID effects are evaluated through DC and low-frequency noise measurements by varying irradiation bias conditions, transistor channel lengths, and fin/finger layouts. The TID response of nFinFETs irradiated under positive gate bias at ultrahigh doses shows a rebound of threshold voltage with significant increase in the 1/ f noise amplitude. The degradation is related to the generation of border and interface traps at the upper corners of STI oxides and at the gate oxide/channel interfaces. In contrast, pFinFETs have the worst degradation due to positive charge trapping in STI oxides, which severely degrades the device transconductance and total drain current, while negligible effects are visible in the threshold voltage and 1/ f noise. The TID sensitivity depends strongly on the transistor layout. Short-channel devices have the best TID tolerance thanks to the influence of halo implantations, while pFinFETs designed with low number of fins have the worst degradation because of high densities of positive charge in the surrounding thick STI oxides. As a guideline for IC design, short-channel transistors with more than 4-fins may be preferred in order to facilitate circuit qualification. [ABSTRACT FROM AUTHOR]

In recent years, with an extensive use of InGaN light-emitting diode (LED), how to assess the LED quality and further improve the LED reliability are very important. In this paper, the noise spectrum measurement techniques are used to assess the electrostatic discharge tolerance and quality of InGaN LED devices. Experimental results show that the noise spectrum measurement distinguishing the LED device reliability is more effective than the current-voltage curve measurement. In the evidence, emission microscope, scanning electron microscope, and transmission electron microscopy images show that the noise source and the cause of failure of the LED device are attributed by the poor quality of the SiO2 and Indium Tin Oxide (ITO) interface. [ABSTRACT FROM PUBLISHER]

Using a large-scale array test circuit, both static characteristics and random telegraph noise (RTN) of in-pixel source follower equivalent transistors of a CMOS image sensor with buried and surface channel transistor structures were statistically evaluated under various current and body bias conditions. The distribution of noise intensities at various operational bias conditions, correlations between RTN amplitude and static characteristics were analyzed. It was found that the RTN amplitude has a positive correlation between the subthreshold swing for both types of transistors. [ABSTRACT FROM AUTHOR]

Nanowire transistors are promising candidates for future electronics applications; however, they generally exhibit higher levels of low-frequency noise compared with traditional MOSFETs. The physics of this noise generation in nanowires needs to be understood for improving the device performance. In this paper, the low-frequency noise in InAs nanowire transistors was studied at different gate voltages before and after passivation by a polymethyl methacrylate (PMMA) layer. Noise levels in nanowire devices can be separated into contributions from the channel and from the contacts by analyzing the noise behavior under different bias conditions for devices with varying channel lengths. It is shown that a noise component, which is independent of channel length, can be attributed to the contacts, and a length-dependent component is attributed to the channel. Applying the PMMA passivation layer over the entire device reduces the noise level generated by the channel, but does not change the noise level generated by the contacts. This paper provides a method to understand, and potentially improve, the noise performance. Operation in a channel-dominated bias regime allows extraction of a Hooge parameter specifically for the channel. PMMA passivation was effective in reducing this channel Hooge parameter from 1.4\times 10^-1 to 1.8\times 10^-3. [ABSTRACT FROM AUTHOR]