Investigation Of Low-frequency Noise Research Articles

Quality Assessment of Processed Graphene Chips for Biosensor Application.

The quality of graphene intended for use in biosensors was assessed on manufactured chips using a set of methods including atomic force microscopy (AFM), Raman spectroscopy, and low-frequency noise investigation. It is shown that local areas of residues on the graphene surface, formed as a result of the interaction of graphene with a photoresist at the initial stage of chip development, led to a spread of chip resistance (R) in the range of 1-10 kOhm and to an increase in the root mean square (RMS) roughness up to 10 times, which can significantly worsen the reproducibility of the parameters of graphene chips for biosensor applications. It was observed that the control of the photoresist residues after photolithography (PLG) using AFM and subsequent additional cleaning reduced the spread of R values in chips to 1-1.6 kOhm and obtained an RMS roughness similar to the roughness in the graphene film before PLG. Monitoring of the spectral density of low-frequency voltage fluctuation (SU), which provides integral information about the system of defects and quality of the material, makes it possible to identify chips with low graphene quality and with inhomogeneously distributed areas of compressive stresses by the type of frequency dependence SU(f).

Investigation of Low-Frequency Noise, in Order to Reduce it During the Operation of Compressor Mounts

Experimental researches of characteristic of low frequency noise and gas dynamic gas pressure pulsations were carried out on experimental compressor mount and in the real industrial conditions. It is shown that gas pressure pulsations are making the main contribution into forming of low frequency noise of compressor mount. New device of reduction of low frequency noise and dynamic pressure pulsations was suggested. The device is allowing us to reach simultaneous efficient reduction of noise and pressure pulsations during operation of compressor mounts and to reduce the risk of the accidents in industrial conditions.

Review of Low-Frequency Noise Properties of High-Power White LEDs during Long-Term Aging.

Low-frequency noise investigation is a highly sensitive and very informative method for characterization of white nitride-based light-emitting diodes (LEDs) as well as for the evaluation of their degradation. We present a review of quality and reliability investigations of high-power (1 W and 3 W) white light-emitting diodes during long-term aging at the maximum permissible forward current at room temperature. The research was centered on the investigation of blue InGaN and AlInGaN quantum wells (QWs) LEDs covered by a YAG:Ce3+ phosphor layer for white light emission. The current-voltage, light output power, and low-frequency noise characteristics were measured. A broadband silicon photodetector and two-color (blue and red) selective silicon photodetectors were used for the LED output power detection, which makes it possible to separate physical processes related to the initial blue light radiation and the phosphor luminescence. Particular attention was paid to the measurement and interpretation of the simultaneous cross-correlation coefficient between electrical and optical fluctuations. The presented method enables to determine which part of fluctuations originates in the quantum well layer of the LED. The technique using the two-color selective photodetector enables investigation of changes in the noise properties of the main blue light source and the phosphor layer during the long-term aging.

Low-Frequency noise investigation of AlGaN/GaN high-electron-mobility transistors

In this paper, the noise Power Spectral Density (PSD) of AlGaN/GaN High-Electron-Mobility Transistors (HEMTs) has been experimentally investigated in linear operation (VD = 50 mV) for different channel lengths (L) and widths (W) at different temperatures (5.32 °C till 100 °C). The origin of the noise will be analyzed to understand the physical mechanisms involved. It is shown that the Low-Frequency (LF) noise is dominated by 1/f noise, originating from number fluctuations. Additionally, in shorter devices, a higher 1/f noise PSD is found. The LF noise characteristics indicate that the AlGaN/GaN HEMTs on silicon substrates can be a promising candidate for analog and Radio Frequency applications (RF).

Low-Frequency Noise Investigation of GaN/AlGaN Metal–Oxide–Semiconductor High-Electron-Mobility Field-Effect Transistor With Different Gate Length and Orientation

In this article, GaN/AlGaN metal–oxide–semiconductor high-electron-mobility field-effect transistors (MOSHEMTs) fabricated on high-resistivity Si (111) substrates have been evaluated using low-frequency (LF) noise measurement. The noise power spectral density (PSD) of devices with different lengths and channel orientations has been characterized in linear operation. No noticeable differences in the electrical and noise PSD characteristics have been observed between the GaN [ $1\overline {1}00$ ] and [ $11\overline {2}0$ ] channel orientations. While most devices are dominated by 1/ ${f}$ noise, originating from number fluctuations, for long devices ( ${L} \ge 1.1~\mu \text{m}$ ), additional generation–recombination (GR) noise has been observed, originating from traps in the GaN layer.

Low frequency noise investigation of n-MOSFET single cells for memory applications

In this paper, we present a detailed investigation of low frequency noise (LFN) for different n-MOSFET devices dedicated for memory applications. We investigate the impact of the gate oxide thickness (GOX) on LFN. We analyzed how the position, the existence and the composition of Lightly Doped Dopant (LDD) implant in the source/drain region affect the LFN performance of the device. The results demonstrates that the thinner gate oxide and the device without LDD improved the noise performance compared the devices with thick GOX and with LDD implants. On the other hand, the absence of LDD implant on one side of the MOSFET didn’t reveal a global trend for all measured devices. Finally, the different LDD implant composition resulted in different LFN performance which is gate area dependent. These results can be used from both process and design engineers to improve the LFN of n-MOSFET.

Characterization of Low-Frequency Excess Noise in CH3NH3PbI3-Based Solar Cells Grown by Solution and Hybrid Chemical Vapor Deposition Techniques.

In this study, detailed investigations of low-frequency noise (LFN) characteristics of hybrid chemical vapor deposition (HCVD)- and solution-grown CH3NH3PbI3 (MAPI) solar cells are reported. It has been shown that LFN is a ubiquitous phenomenon observed in all semiconductor devices. It is the smallest signal that can be measured from the device; hence, systematic characterization of the LFN properties can be utilized as a highly sensitive nondestructive tool for the characterization of material defects in the device. It has been demonstrated that the noise power spectral densities of the devices are critically dependent on the parameters of the fabrication process, including the growth ambient of the perovskite layer and the incorporation of the mesoscopic structures in the devices. Our experimental results indicated that the LFN arises from a thermally activated trapping and detrapping process, resulting in the corresponding fluctuations in the conductance of the device. The results show that the presence of oxygen in the growth ambient of the HCVD process and the inclusion of an mp-TiO2 layer in the device structure are two important factors contributing to the substantial reduction in the density of the localized states in the MAPI devices. Furthermore, the lifetimes of the MAPI perovskite-based solar cells are strongly dependent on the material defect concentration. The degradation process is substantially more rapid for the devices with higher initial defect density compared to the devices prepared under optimized conditions and structure that exhibit substantially lower initial trap density.

Low frequency noise investigation of 2–3 μm GaSb-based laser diodes

A detailed noise study of mid-infrared 2–3μm wavelenght GaSb-based type-I ridge-waveguide laser diodes (LDs) has been carried out using the low frequency noise spectroscopy. Different samples having slightly different heterostructures, differently packaged, with and without facet passivation have been investigated. The activation energies of trap levels, associated with additional generation-recombination (g–r) noise components in noise spectra at small current region before the threshold, have been determined. It was shown that at particular forward currents the mode-hopping effect dominates during LD lasing operation. It was demonstrated that small differences in LD heterostructure and waveguide layers have got the largest influence to LD noise characteristics while influence of the absence of facet passivation, linking to noise generation centers at the cleaved semiconductor interface, and package type is much weaker.

Investigation of Low-Frequency Noise in Nonvolatile Memory Composed of a Gate- All-Around Junctionless Nanowire FET

Low-frequency noise (LFN) behaviors, characterized with an SONOS-based gate-all-around junctionless nanowire (JLNW), are investigated to determine the suitability of this type of NW as a memory cell structure. LFN exhibits a 1/ $f$ -shape and is described by a carrier number fluctuation noise model. It is found that the proposed device structure shows a low level of device-to-device variation and high immunity against Fowler–Nordheim tunneling stress. Due to the centered conduction path in the JLNW device, the impact of correlated mobility fluctuations on the LFN is insignificant. The trapped charge in the nitride layer of the Silicon(Poly-Si)-oxide(SiO2)-nitride(SiN x )-oxide(SiO2)-silicon(Single-crystalline) (SONOS) device also negligibly influences the LFN. The NW width-dependence is clarified in terms of the effects of the oxide trap density and source/drain series resistance under a fresh and a programmed state.

Investigation of low-frequency noise of 28-nm technology process of high-k/metal gate p-MOSFETs with fluorine incorporation

In this study, the properties of dielectric traps by the impact of Fluorine (F) implantation on 1/f noise and the random telegraph noise (RTN) of high-k/metal gate (HK/MG) p-type metal–oxide–semiconductor field-effect transistors (pMOSFETs) were investigated. The incorporation of F has been identified as an effective method to passivate oxygen vacancies, defect sites, and reduce the gate leakage current in pMOSFETs. Compared with a control device, the F-implanted HK/MG devices show that the trap positions were closer to the SiO2 interfacial layer (IL)/Si channel. Furthermore, we found that F implantation could result in a smaller tunneling attenuation length (λ) and smaller slow oxide interface trap density (Nt).

Low-frequency noise investigation of n-channel 3D devices

In this paper, the low-frequency (LF) noise in standard n-channel triple-gate Bulk FinFETs has been experimentally investigated with variation in the fin widths (WFin), channel lengths (L) and gate dielectric. The origin of the noise will be analyzed in order to understand the physical mechanisms involved in 3D device architectures. Although the device scaling brings the idea of noise reduction, we show the opposite behavior because already single electron trapping has a marked impact on the device operation. Significant variation in the noise spectral density has been observed, which is related to the random occurrence of excess Lorentzian components (1/f2-like), associated with generation–recombination (GR) noise. In addition, the gate-voltage-dependent GR noise peaks have been studied, which are assigned to gate oxide traps.

Assessment of technological and geometrical device parameters by low-frequency noise investigation in SOI omega-gate nanowire NMOS FETs

A study of the gate oxide/channel interface quality in ultra-scaled SOI omega-gate nanowire NMOS FETs with cross-section as small as 10nm×10nm is experimentally presented by low-frequency noise measurements. The noise study has been efficiently applied for the characterization of various technological parameters, including strained channel, additional hydrogen anneal, or channel orientation difference. A method for rigorous contribution assessment of the two oxide/channel interfaces (top surface vs. side-walls) is also demonstrated. Quality of the interface is slightly altered among the 4-types of technological parameters and the structural variety down to nanowire. However, an excellent quality of Hf-based high-k/metal gate stack is observed and sustained in all the devices. In particular, efficient tensile strain stressor is demonstrated with high enhancement of the NMOS FET performance and preserved 1/f noise performance fulfilling the requirement for future CMOS logic node stated in the international technology roadmap for semiconductors.

Investigation of Low-Frequency Noise in p-type Nanowire FETs: Effect of Switched Biasing Condition and Embedded SiGe Layer

The low-frequency noise (LFN) of a p-type nanowire FET (p-NWFET) was characterized and compared with that of an n-type NWFET (n-NWFET) in terms of dominant noise source and its location in the channel region. An inverse proportional dependence of the noise level on channel diameter was observed in the p-NWFET but not in the n-NWFET. The LFN was observed to be mainly generated by Hooge mobility fluctuation in the p-NWFET. Under a switched biasing condition, p-NWFET showed no substantial LFN reduction (in contrast to the n-NWFET), indicating that the carrier number fluctuation was insignificant. This was due to the compressive stress induced by embedded SiGe with heavier transverse effective hole mobility.

Analysis of mode-hopping effect in Fabry–Pérot multiple-quantum well laser diodes via low frequency noise investigation

Comprehensive investigation of noise characteristics and radiation spectrum with special attention to the mode-hopping effect of Fabry–Pérot (FP) multiple quantum well laser diodes (LDs) have been carried out: laser radiation spectra, optical and electrical fluctuations and cross-correlation factor between them have been measured under stable and mode-hopping operation. At the mode-hopping that occurs at particular operation conditions (injection current and temperature) LD radiation spectrum is unstable in time, very intensive and highly correlated Lorentzian-type optical and electrical fluctuations are observed. Characteristic time of physical processes that take part in LD structure during mode-hopping is ranged from microseconds to milliseconds. These processes are caused by the carrier generation and recombination in the centers formed by the defects in barrier layer (in the active region).

Low-Frequency Noise in Schottky-Barrier-Based Nanoscale Field-Effect Transistors

Investigation of low-frequency noise in nanoscale Schottky-barrier (SB)-based field-effect transistors (SB-FETs) is of prime importance due to its large amplitude in emerging bottom-up devices. In addition, noise can give additional information on charge transport mechanisms. In this paper, we study the 1/ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> noise in nanoscale silicon-on-insulator SB-FETs. An unexpected feature is the clear contribution of the SB to the noise even if the barrier height is lower than 100 meV. Barrier modulation techniques such as dopant segregation are used to tune the barrier height. We propose a generic formulation for low-frequency noise that is applicable to any diffusive SB-FETs.

A comparative 1/ f noise study of GeOI wafers obtained by the Ge enrichment technique and the Smart Cut technology

This paper presents an experimental investigation of Low-frequency Noise (LFN) measurements on Germanium-On-Insulator (GeOI) PMOS transistors processed on different wafers. The wafers are obtained by Ge enrichment technique and by Smart Cut™ technology. The slow oxide trap densities of back interface are used as a figure of merit to evaluate the process. The Smart Cut™ process is evaluated by studying GeOI pMOSFETs, and the enrichment process by studying Si 1− x Ge x ( x = 25% and 35%) pMOSFETs. The buried oxide is used as a back gate for experimental purposes. The extracted values are of the same order of magnitude for both processes and are close to those of state of art buried oxide SiO 2/Si interfaces, demonstrating that both the Smart Cut™ and enrichment techniques produce equally good quality interfaces.

Characterization of impact of process options in Germanium-On-Insulator (GeOI) high-k & metal gate pMOSFETs by low-frequency noise

The impact of technological processes on Germanium-On-Insulator (GeOI) noise performance is studied. We present an experimental investigation of low-frequency noise (LFN) measurements carried out on (GeOI) PMOS transistors with different process splits. The front gate is composed of a SiO 2/HfO 2 stack with a TiN metal gate electrode. The result is an aggressively reduced equivalent oxide thickness (EOT) of 1.8 nm. The buried oxide is used as a back gate for experimental purposes. Front and back gate interfaces are characterized and the slow oxide trap densities are extracted. The obtained values are comprised between 5 × 10 17 and 8 × 10 18 cm −3eV −1. No correlation between front interface trap density and front interface mobility is observed. We underline a strong correlation between rear interface trap density and rear interface mobility degradation. The impact of Ge film thickness is equally studied. For thin films, the measured drain-current noise spectral density shows that LFN can be described by the carrier fluctuation model from weak to strong inversion. For thicker film devices, in weak inversion the LFN can be described by the mobility fluctuation model and in strong inversion the LFN is described by the carrier fluctuation model. The α H parameter for these devices is 1.2 × 10 −3. These results are significant for the future development of GeOI technologies.

Effect of concentration on low-frequency noise of multiwall carbon nanotubes in high-density polyethylene matrix

Transport and noise measurements of multiwall carbon nanotubes in high-density polyethylene matrix are reported. In these composites current transport occurs through a random tunnel junctions network, formed by adjacent carbon nanotubes. Low-frequency noise investigations reveal a 1/f behavior induced by resistance fluctuations. An unusual temperature dependence in samples with different nanotube concentration is found. This can be explained by a transition from a fluctuation-induced tunneling mechanism to a thermally activated regime, occurring at increasing nanotube concentration and resulting in a decrease in the overall noise.

Investigation of Low-Frequency Noise in N-Channel FinFETs From Weak to Strong Inversion

This paper presents the low-frequency noise (LFN) characteristics of symmetric double-gate n-FinFETs from weak to strong inversion at low drain bias. The noise-generation mechanism is investigated. The measured drain-current noise spectral density shows that LFN in the weak-inversion subthreshold region can be well described by the mobility-fluctuation model due to volume-inversion conduction behavior, which is very different from those normally observed in the bulk NMOS. The analytical expression for the drain-current noise spectral density is derived, with the Hooge parameter alpha <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> being extracted. In the strong-inversion linear region, the gate-voltage dependence of the room-temperature noise data agrees with the number-fluctuation model, but the slope of the frequency dependence is less than one. To determine the causes of the observed deviation from the unity slope, detailed measurements of the temperature dependence of the noise power spectra are performed, and results from two devices are presented in this paper. It is found that both the magnitude and the frequency dependence of the drain-voltage noise spectral density vary greatly in the range between 223 K and 383 K. The experimental results are compared with two models derived based on the Dutta-Horn and the McWhorter models. It is shown that the thermal-activation model of Dutta-Horn is more convincing than the latter, which shows that the noise is due to the capture and emission of carriers by oxide traps through thermal activation. The surface trap density at specific activation energy is extracted.

Investigation of Low Frequency Noise

Investigation of Low Frequency Noise