Low-frequency Noise Measurements Research Articles

Noise reduction by bias cooling in gated Si/Six Ge1−x quantum dots

Silicon–germanium heterostructures are a promising quantum circuit platform, but crucial aspects, such as the long-term charge dynamics and cooldown-to-cooldown variations, are still widely unexplored quantitatively. In this Letter, we present the results of an extensive bias cooling study performed on gated silicon–germanium quantum dots with an Al2O3 dielectric. Over 80 cooldowns were performed in the course of our investigations. The performance of the devices is assessed by low-frequency charge noise measurements in the band of 200 μHz to 10 mHz. We measure the total noise power as a function of the applied voltage during cooldown in four different devices and find a minimum in noise at 0.7 V bias cooling voltage for all observed samples. We manage to decrease the total noise power median by a factor of 6 and compute a reduced tunneling current density using Schrödinger–Poisson simulations. Furthermore, we show the variation in noise from the same device in the course of eleven different cooldowns performed under the nominally same conditions.

Evaluating the uncertainty of laboratory measurements of low-frequency impact noise

Impact noise at low frequencies, specifically the third-octave bands below 100 Hz, is important to occupant reaction and are, therefore, routinely measured in field impact testing. For laboratory impact testing, the situation is less clear. Because the measured levels depend strongly on the specifics of the test chamber, it is expected that the reproducibility of low-frequency impact noise between laboratories to be poor and the translation to field measurements to be difficult. Despite these difficulties, the authors will demonstrate that it is possible to extract useful low frequency information from laboratory testing. The utility of laboratory testing for design of low-frequency impact noise is discussed.

Strong contact resistance effects on vertical carrier density profile and surface trap density in WSe2 multilayers

Conducting channel migration depending on the thickness of 2D multilayers has been demonstrated theoretically and experimentally by ascribing it to the high interlayer barrier and thickness-dependent carrier mobility via an electrostatic gate and drain bias. However, the unique charge carrier transport feature is significantly suppressed when a high contact resistance is exhibited at the metal-to-2D semiconducting multilayers, in addition to the inherent tunneling barrier between neighboring layers. Herein, we report strong channel access contact resistance effects on the vertical carrier density profile and surface trap density along the thickness of WSe2 multilayer transistors. For the constructed top-contact electrodes demonstrating pseudo-ohmic behavior, we observed clear double humps in the second derivative of the transconductance (dgm) curves, implying conducting channel migration along the c-axis of the WSe2 multilayers, regardless of the drain bias (VD) conditions. Meanwhile, at the bottom-contact electrodes, demonstrating a relatively high contact resistance effect, the second hump of dgm exclusively appears at high VD regimes (3.0 V ≤ VD), signaling the restricted channel migration caused by poor contact quality, even in identical WSe2 multilayers. We further confirmed this distinct feature in dgm curves by connecting the top and bottom electrodes to support our observations. Furthermore, low-frequency noise measurements were performed to determine the surface trap density of the supporting dielectrics and the relevant carrier scattering mechanism. Our study provides valuable insight into the effects of contact resistance on carrier transport and the scattering mechanism in WSe2 multilayer transistors, shedding light on the optimization of device performance and contact quality.

Low Frequency Noise Behavior in Resistive Memory Devices with Hf/HfO2 Stack

Resistive-random-access-memory (RRAM) devices are considered to be one of the most potential candidates of next generation emerging memory technologies due to their excellent device properties, such as high density, low power, low voltage, and high speed. RRAM features simple metal–insulator–metal (MIM) structures and is fully compatible with traditional CMOS fabrication processes. Low-frequency noise (LFN) measurement is a technique to characterize electrically the trap-assisted conduction processes in dielectrics. In this work, we report the LFN characteristics of Hf/HfO2-based bipolar RRAM and investigate the current conduction mechanism and internal physics.

Flicker Noise in Resistive Gas Sensors-Measurement Setups and Applications for Enhanced Gas Sensing.

We discuss the implementation challenges of gas sensing systems based on low-frequency noise measurements on chemoresistive sensors. Resistance fluctuations in various gas sensing materials, in a frequency range typically up to a few kHz, can enhance gas sensing by considering its intensity and the slope of power spectral density. The issues of low-frequency noise measurements in resistive gas sensors, specifically in two-dimensional materials exhibiting gas-sensing properties, are considered. We present measurement setups and noise-processing methods for gas detection. The chemoresistive sensors show various DC resistances requiring different flicker noise measurement approaches. Separate noise measurement setups are used for resistances up to a few hundred kΩ and for resistances with much higher values. Noise measurements in highly resistive materials (e.g., MoS2, WS2, and ZrS3) are prone to external interferences but can be modulated using temperature or light irradiation for enhanced sensing. Therefore, such materials are of considerable interest for gas sensing.

Low-frequency noise and impedance measurements in Auger suppressed LWIR N+p(π)P+n+ HgCdTe detector

The paper reports on the electrical performances of LWIR N+p(π)P+n+ HgCdTe photodiodes optimized for λcut-off(50%) ≈ 10.6 μm at T = 230 K. Presented work mainly focuses on the region where negative resistance is observed due to Auger suppression effect. Previous reports showed that for such detectors it is usually observed at temperature conditions above ∼120 K for devices designed to operate in HOT conditions. The studies were carried out over a wide temperature range using few measurement methods: dark current, low-frequency noise, and impedance components. The results were also investigated as a function of the applied bias. A detailed analysis of the results were presented to show the influence of operating conditions when the detector works in negative resistance region. In these regions, we observed a dynamic change of the complex impedance from both parallel capacitance and resistance. The low-frequency noise measurements showed that in the negative resistance region, the noise spectral density is still rising with the reverse bias voltage despite reduction of the dark current by Auger suppression and the noise-current related intensity coefficient α is also still tends to rise. For temperatures above 160 K the noise-bias voltage interdependence near Si ∼ V2 was noticed. Moreover, the studies showed that the noise-temperature behaviour depends on the applied bias. The results obtained in experiments were discussed based on the current knowledge of these devices to verify and explain the behaviours of the dark current, noise and impedance-related parameters.

KHz Linewidth Laser Characterization using Low Frequency and Excess Noise Measurements

kHz Linewidth Laser Characterization using Low Frequency and Excess Noise Measurements

Study of drone self-noise estimation for low frequency noise measurement by multicopter drone

We are developing low-frequency noise measurement system with multi-copter type drone. The biggest obstacle to measurements is drone self-noise. Therefor the system records environment noise and propeller rotation timing signal and removes the self-noise from the recording offline. For a high cancellation performance, accurate self-noise estimation is very important to remove self-noise from recordings. Focusing on the reproducibility of the self-noise for each rotation, we proposed a method for estimating self-noise at arbitrary rotations during flight from prerecording self-noise data. When the proposed system was mounted on a toy drone and its self-noise cancellation performance was evaluated, high cancellation performance was obtained in the low frequency region. In the study, In this paper, we report a method and its evaluation for estimating the self-noise of the propeller 1 axis from the rotation signal of the propeller axis of the drone.

Review and comments on ANSI-ASA S12.9 part 7 measurement of low frequency and infrasound

ANSI-ASA S12.9 Quantities and Procedures for Description of Environmental Sound, Part 7: Measurement of Low Frequency Noise and Infrasound Outdoors and in the presence of Wind and Indoors in Occupied Spaces is currently being evaluated for potential revisions. This presentation will cover proposed revisions to the standard and reasoning used to arrive at these suggested revisions.

Benefits of using ANSI/ASA S12.9 -2020/Part 7: “Measurement of environmental sound: Measurement of low-frequency noise and infrasound outdoors and in the presence of wind and indoors in occupied spaces.”

I was invited and honored by Dr. Paul Schomer to Chair working group S12/WG 54 for Part 7 of ANSI S12.9. The working group had 23 learned members all at the reasonable disposal of the Chair. At the start I knew the technical tasks that would have to be done and it would be a time-consuming process, at least a year; completion took over three years. Some of the fundamental tasks required were (a) Define and quantify wind-induced-noise (WIN) for standard wind screen measurements and with upgraded wind protection to lower WIN, (b) Define conversion corrections necessary between post-mounted above grade and ground plane mounted microphones, and (c) Define a repeatable technique for measuring pressure levels outside and inside structures to characterize noise reduction NR in 1/3 octave bands for the facade of the structure. These tasks were completed with much effort by numerous group members. The standard may be consulted for analyses and reference, particularly Annexes A through D, as well as for authoritarian standard purposes. This presentation will outline the many valuable procedures in the standard for measuring low frequency noise and infrasound.

Total-Ionizing-Dose Effects at Ultrahigh Doses in AlGaN/GaN HEMTs

Total-ionizing-dose effects in AlGaN/GaN HEMTs are evaluated by DC and low frequency noise measurements. Devices with and without passivation layers are irradiated with 10-keV X-rays up to 100 Mrad(SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) under different bias conditions. Irradiated devices show significant electrical shifts in threshold voltage and transconductance. At doses <10 Mrad(SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ), the TID-induced effects are related to the passivation of pre-existing acceptor-like defects via hole capture, which induces negative threshold voltage shifts and improvement of transconductance. At doses >10 Mrad(SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ), dehydrogenation of defects and impurity complexes leads to the creation of acceptor-like defects, which degrade the transconductance, shift positively the threshold voltage, and increase the low-frequency noise. Effects are enhanced in unpassivated devices and when the gate is biased at high voltage.

Study on low-frequency noise characteristics of hydrogen-terminated diamond FETs

In this work, the low frequency noise (LFN) characteristics of Hydrogen-terminated diamond FETs are investigated. Both generation-recombination (GR) noise and flicker noise (1/f noise) are found to contribute to the LFN spectrum. The characteristic frequency of f01 = 0.1 Hz, f02 = 30 Hz, f03 = 300 Hz and corresponding effective trap density (Neff) of the GR centers are obtained. By changing the LFN measurement temperature, a trap activation energy level (Ea) of 0.12 eV is extracted from an Arrhenius plot. The dominant mechanism of the 1/f noise for the H-terminated diamond FETs follows the correlated mobility fluctuations (CMF) model. By fitting the experimental data to the CMF model, the trap density and scattering coefficient of the carriers are extracted to be 6.4×1020 eV−1 cm−3 and 4×105 V·s/C. At last, the trap density of the H-terminated diamond FETs is compared with other state-of-the-art GaN and Si based devices. A moderate trap density was obtained without any interface optimization, suggesting that H-terminated diamond FETs could be a promising future technology for power electronics.

Novel Y-function based strategy for parameter extraction in S/D asymmetric architecture devices and low frequency noise characterization in GAA Si VNW pMOSFETs

In this work, DC and low frequency noise measurements are performed in p-channel gate-all-around (GAA) silicon vertical nanowire (Si VNW) MOSFETs. The DC measurements highlight asymmetry in the drain current and transconductance transfer characteristic even in linear operation, at an applied drain voltage of −50 mV. A novel Y-function based strategy for parameter extraction in S/D asymmetric devices is proposed. This novel strategy allows the estimation of the value of each access resistance, from source and from drain sides, respectively, and allows overcoming the device asymmetry to provide an accurate extraction of the main DC parameters. The low-frequency noise studies on forward and reverse operation mode, demonstrate that the 1/f noise in both modes can be explained by the correlated carrier number (Δn) and mobility fluctuation (Δμ) mechanisms, with additional contribution of the access resistance noise in strong inversion.

Comparative analysis of low-frequency noise based resistive switching phenomenon for filamentary and interfacial RRAM devices

We investigate the low-frequency noise (LFN) characteristics of resistive switching random access memory (RRAM) devices with metal–insulator–metal structures of TiN/Ti/TiO2/TiN (filamentary) and TiN/Ti/TiO2/HfO2/TiN (interfacial). By comparing filamentary and interfacial RRAM devices, we stipulate guidelines for noise sources according to the resistance states or resistive switching mechanisms of RRAM device. In filamentary RRAM devices, the dominant noise source in the low resistance state is the localized oxygen vacancies, whereas the noise characteristics in the high resistance state represent a bulk effect. In interfacial RRAM devices, the noise characteristics in both resistance states represent the bulk effect. The physical mechanism of the multilevel cell operation is inferred by the I–V characteristics in both Icc and Vreset control modes. Specifically, the changes in the structure of the conductive filament inside the switching layer can be confirmed through LFN measurement.

Distribution of Process Induced Traps in Ozone Annealed Indium-Gallium-Zinc-Oxide Film Determined From Noise Characterization

Space-energy distribution of process induced traps was extracted from random telegraph noise (RTN) characterization on ozone (O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) annealed Indium-Gallium-Zinc-Oxide (IGZO) metal-oxide-metal (MOM) capacitors. It was found that, O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> anneal increases both deeper and shallower traps in IGZO all the way to conduction band edge (CB) compared to the as-deposited film, and results in higher aggregate trap density as found from low frequency noise measurement. Extracted trap distribution was benchmarked with that in as-deposited and thermal annealed films, and was found convenient to interpret low field current degradation in IGZO due to O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> anneal.

Probing hidden conduction mechanisms in diced silicon solar cells by low frequency noise analysis

Electrical low frequency noise (LFN) measurements are utilized in this work, in order to identify parasitic low voltage transport mechanisms in diced aluminum back surface field (Al-BSF) photovoltaic (PV) cells, which cannot be identified by I–V characterization. A detailed method of LFN analysis is proposed, taking into account the co-existence of various transport mechanisms, that typically occur in parallel in such devices. A precise examination of the 1/f noise level dependency with both current and voltage, combined with static I–V characterizations at various temperatures, enabled the identification of two flicker noise sources appearing at different current regions: one attributed to local linear shunt mechanisms and a second one to a fluctuation in a nonlinear parasitic conductivity localized at the samples’ edges. The latter source exhibits noise signatures resembling either tunneling or Poole-Frenkel transport, while excluding Shockley-Read-Hall recombination processes. This hypothesis was further verified by measurements of thermal activation energies typical of tunnel and Poole-Frenkel conduction mechanisms.

Electrospinning‐Driven Binary Oxide Nanofiber Networks with Tunable Amorphous Microstructure for Booming Transistors and Circuits Operation

AbstractAlthough In2O3 nanofibers (NFs) are regarded as one of the active channel materials for next‐generation, low‐cost thin‐film transistors (TFTs), these NFs‐based devices still suffer from the degraded carrier mobility and operational instability, limiting the ability of such devices to replace current polycrystalline silicon technologies. Here, it is shown that nanofiber channel transistors with high electron mobility and operational stability can be achieved by selectively doping Zn element into electrospun In2O3 NFs. By precisely manipulating the doping level during NFs fabrication, their crystallinity, surface morphology, and corresponding device performance can be regulated reliably for enhanced transistor performances. It has been detected that InZnO/SiO2 TFTs with an optimized Zn doping concentration of 50% have demonstrated the high field‐effect mobility (µFE) of 6.38 cm2 V−1 s−1, the larger ION/IOFF of 4.12 × 107 and operation in the energy‐efficient enhancement‐mode. Low frequency noise (LFN) measurements have displayed that the scattering and defects inside the NFs are effectively suppressed by the particular microstructure. When integrating ALD‐derived Al2O3 films as the gate dielectric into TFTs devices, their electron mobility and ION/IOFF can be further improved to 37.82 cm2 V−1 s−1 and 2.92 × 108, respectively. To demonstrate the potential toward more complex logic applications, a low voltage resistor‐loaded unipolar inverter is built by using InZnO/Al2O3 TFT, exhibiting a high gain of 20.95 and full swing characteristics. These optimized parameters have demonstrated the significant advance of this electrospinning technique toward practical applications for high performance and large‐scale electronics.

Synthesis of a large area ReS2 thin film by CVD for in-depth investigation of resistive switching: effects of metal electrodes, channel width and noise behaviour.

The anisotropic crystal structure and layer independent electrical and optical properties of ReS2 make it unique among other two-dimensional materials (2DMs), emphasizing a special need for its synthesis. This work discusses the synthesis and in-depth characterization of a 1 × 1 cm2 large and few layered ReS2 film. Vibrational modes and excitonic peaks observed from the Raman and photoluminescence (PL) spectra corroborated the formation of a ReS2 film with a 1.26 eV bandgap. High resolution transmission electron microscopy (HRTEM) images and selected area electron diffraction (SAED) patterns inferred the polycrystalline nature of the film, while cross-sectional field emission scanning electron microscopy (FESEM) indicated planar growth with ∼10 nm thickness. The chemical composition of the film analysed through X-ray photoelectron spectroscopy (XPS) indicated the formation of a ReS2 film with a Re : S atomic ratio of 1 : 1.75, indicating a small amount of non-stoichiometric RexSy. Following the basic characterization studies, the ReS2 film was tested for resistive switching (RS) device application in which the effects of different metal electrodes (Pt/Au and Ag/Au) and different channel widths (200, 100, and 50 μm) were studied. The highest memory window equal to 108 was obtained for the Ag/Au electrode while Pt/Au showed a memory window of 102. RS for the former was ascribed to the formation of a conducting filament (CF) because of the migration of Ag+ ions, while defect mediated charge carrier transport led to switching in the Pt/Au electrode. Furthermore, the RHRS/RLRS ratio achieved in this work (108) is also of the highest magnitude reported thus far. Furthermore, a comparison of devices with Ag/Au electrodes but with different channel widths (50, 100 and 200 μm) gave insightful results on the existence of multiple resistance states, device endurance and retention. An inverse relationship between the retention time and the device's channel width was observed, where the device with a 50 μm channel width showed a retention time of 48 hours, and the one with a 200 μm width showed stability only up to 3000 s. Furthermore, low frequency noise measurements were performed to understand the effect of defects in the low resistance state (LRS) and the high resistance state (HRS). The HRS exhibited Lorentzian noise behaviour while the LRS exhibited Lorentzian only at low current bias which converged to 1/f noise at higher current bias.

Probing charge traps at the 2D semiconductor/dielectric interface.

The family of 2-dimensional (2D) semiconductors is a subject of intensive scientific research due to their potential in next-generation electronics. While offering many unique properties like atomic thickness and chemically inert surfaces, the integration of 2D semiconductors with conventional dielectric materials is challenging. The charge traps at the semiconductor/dielectric interface are among many issues to be addressed before these materials can be of industrial relevance. Conventional electrical characterization methods remain inadequate to quantify the traps at the 2D semiconductor/dielectric interface since the estimations of the density of interface traps, Dit, by different techniques may yield more than an order-of-magnitude discrepancy, even when extracted from the same device. Therefore, the challenge to quantify Dit at the 2D semiconductor/dielectric interface is about finding an accurate and reliable measurement method. In this review, we discuss characterization techniques which have been used to study the 2D semiconductor/dielectric interface. Specifically, we discuss the methods based on small-signal AC measurements, subthreshold slope measurements and low-frequency noise measurements. While these approaches were developed for silicon-based technology, 2D semiconductor devices possess a set of unique challenges requiring a careful re-evaluation when using these characterization techniques. We examine the conventional methods based on their efficacy and accuracy in differentiating various types of trap states and provide guidance to find an appropriate method for charge trap analysis and estimation of Dit at 2D semiconductor/dielectric interfaces.

Refined DC and Low-Frequency Noise Characterization at Room and Cryogenic Temperatures of Vertically Stacked Silicon Nanosheet FETs

In this work, two types of gate-all-around (GAA) vertically stacked silicon nanosheet (NS) FETs are investigated, the main difference being the vertical distance between the stacked NSs. Principal electrical parameters are estimated at room and liquid nitrogen temperatures using a refined <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Y}$ </tex-math></inline-formula> -function methodology, the main advantage being that no extra iterative steps are necessary. The results are confirmed using other derivative dc parameter estimation methodologies. Low-frequency noise measurements evidence variability of the flat-band voltage noise and correlation between the noise level and the low field mobility. The dominant flicker noise mechanism is related to the correlated mobility and carrier number fluctuation mechanism with access resistance noise contribution in very strong inversion. The impact of the access resistance on the estimation of the Coulomb scattering coefficient is evidenced.