Low-frequency Noise Behavior Research Articles

Low-frequency noise in amorphous indium–gallium–zinc oxide thin-film transistors with an inverse staggered structure and an SiO2 gate insulator

We report the low-frequency noise (LFN) behavior of amorphous indium–gallium–zinc oxide thin-film transistors with an inverse staggered structure and an SiO2 gate insulator. The normalized noise power spectral density depended on channel length, L, with the form 1/L2, and on the gate bias voltage, VG, and threshold voltage, VTH, with the form 1/(VG − VTH)β where 1.5 < β < 2.1. In addition, the scattering constant α was less than 105 Ω. These results suggest that the contact resistance has a significant role in the LFN behavior and the charge-carrier density fluctuation is the dominant origin of LFN.

Analysis of flicker noise in two-dimensional multilayer MoS2 transistors

Using low-frequency noise (LFN) analysis, we examined the quality of the semiconductor, oxide, and oxide–semiconductor interface of back-gated multilayer MoS2 transistors. We also investigated the mechanism of the LFN and extracted γ exponents from the LFN behavior, 1/fγ; the value of γ was &amp;gt;1 at negative gate bias because of active slow traps. As VG increased, the slow traps were filled and thus γ decreased, stabilizing at ≈0.95. Various other parameters extracted from the LFN indicated that the carrier number fluctuation (Δn) model was the dominant origin of the LFN. The multilayer MoS2 structure had better noise immunity than a single-layer case in air.

Band offsets and electrical stability characterization of Zr-doped ZnO thin-film transistors with a Gd2O3 gate insulator

The performance of zirconium (Zr) doped zinc oxide (ZnO) thin-film transistors (TFTs) grown using an RF co-sputtering method is investigated. This study determines the properties of ZrZnO channel and ZnO channel TFT devices using reactively evaporated Gd2O3 as a gate dielectric. The energy discontinuity in the band offsets (ΔEC and ΔEV) of the Gd2O3/ZrZnO and Gd2O3/ZnO heterostructures is measured using X-ray photoelectron spectroscopy (XPS). The Gd2O3/ZrZnO TFTs exhibit a better conduction band offset (ΔEC=3.98) and a better electrical stability than Gd2O3/ZnO (ΔEC=3.62) TFTs. The ZrZnO device achieves a threshold voltage (VTH) of −0.96V; the sub-threshold slope (S.S) is 0.21V/decade, the Ion/Ioff ratio is 2.46×106, and the field-effect mobility is 1.06cm2/V-s. In addition, the low-frequency noise (LFN) behavior of ZrZnO and ZnO thin-film transistors is also observed. The fluctuation caused by trapping/detrapping can be reduced by the Zr dopants of the TFT devices. The Hooge’s parameters are determined to be αH=1.18×10−1 for the ZrZnO TFTs and αH=5.5×105 for the ZnO TFTs.

Analysis of low-frequency noise in the amorphous indium zinc oxide thin film transistors

Properties of low-frequency noise in the amorphous InZnO thin film transistors have been investigated in this paper. Due to the emission and trapping processes of carriers between trapping states located in the interface between the IZO layer and gate insulator, the drain current spectral density shows a 1/fγ(γ =0.75) low-frequency noise behavior. In addition, the normalized drain current spectral density is decreased linearly with the increase of gate length and width. This property confirms that the low-frequency noise in the IZO TFTs is due to the flicker noise in the channel, the contribution of source/drain contact and parasitic resistances can be ignored. Finally, based on the number fluctuation theory and the mobility fluctuation theory, the γ and average Hooge's parameters have been extracted to estimate the quality of devices and materials.

On the Oxide Trap Density and Profiles of 1-nm EOT Metal-Gate Last CMOS Transistors Assessed by Low-Frequency Noise

The low-frequency noise behavior of replacement metal gate high- k/metal-gate MOSFETs with an equivalent oxide thickness of the SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> bilayer in the range ~ 1 nm has been investigated. It will be shown that both the average trap density and its profile derived from the frequency exponent γ of the flicker noise spectra are mainly determined by the interfacial layer (IL) oxide processing, with a higher trap density corresponding with a thinner chemical oxide, compared with a ≤ 1-nm thermal SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> IL. The thickness of the HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> layer and the metal gate fill has only a marginal impact on the noise power spectral density. It will also be shown that for the extraction of the trap density profiles from the 1/f <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">γ</sup> noise spectra accurate values for the tunneling effective mass and barrier height are required.

Excess noise in InAs/GaSb type-II superlattice pin-photodiodes

We characterize the low-frequency white noise behavior of a large set of InAs/GaSb superlattice infrared pin-photodiodes for the mid-wavelength infrared regime at 3–5μm. For diodes with an increased dark current in comparison to the dark current of generation–recombination limited bulk material, the standard shot-noise model fails to describe the noise experimentally observed in the white part of the spectrum. Instead, we find that McIntyre’s noise model for avalanche multiplication processes is compliant with our data. We suggest that within high electric field domains localized around macroscopic defects, avalanche multiplication processes leading to increased dark current and excess noise.

Lessons Learned from Low-Frequency Noise Studies on Fully Depleted UTBOX Silicon-On-Insulator nMOSFETs

The low-frequency (LF) noise behavior of Fully Depleted (FD) Ultrathin Buried Oxide (UTBOX) Silicon-on-Insulator (SOI) nMOSFETs is described from the perspective of the three major noise sources: 1/f-like or flicker noise, associated with carrier trapping/detrapping in the gate oxide; Generation-Recombination (GR) noise due to processing-induced defects in the thin silicon film and single-oxide-trap-related Random Telegraph Noise (RTN). It is shown that the fully depleted nature of the thin silicon films (<20 nm) offers the unique opportunity to study and demonstrate the front-back coupling of the 1/f noise. At the same time, a large variability is induced in the noise magnitude by the Lorentzian noise, related with GR events through defects in the silicon film. A method to discriminate oxide- from film-defects-related Lorentzian noise is pointed out. Finally, the implications for future fully depleted fin-type of devices will also be discussed.

Low-Frequency Noise in High-K and SiO2 UTBOX SOI nMOSFETS

The impact of different gate dielectrics on the low-frequency (LF) noise behavior is investigated in UTBOX SOI nMOSFETs. Hafnium silicate (HfSiO) devices are compared to silicon dioxide (SiO2) ones in terms of low-frequency noise apart from the analysis of both front and back-channels. Despite the improvement of process steps for obtaining good dielectric layers, high-k devices have shown elevated current noise spectral density due to the higher number of traps which also degrades the front-channel mobility. Although the buried oxide (BOX) of both wafers is formed by thermal SiO2, the strong electrostatic coupling between front and back-channels has resulted in a worse noise performance for high-k devices even at the back interface.

DC and low-frequency noise behavior of the conductive filament in bipolar HfO2-based resistive random access memory

This paper addresses the low frequency noise (LFN) properties of bipolar HfO2-based resistive random access memory cells. It is shown that the devices exhibit a current on–off window up to 70 which is almost independent of the temperature in the range 30–180 °C. The experimental current–voltage curves in both resistance states are well reproduced by the quantum point contact model. LFN spectrum is typically characterized by 1/f noise in the low resistance state (LRS), while individual lorentzian components are often observed superimposed to the background 1/f noise in the high resistance state (HRS). Both LFN types are ascribed to defects fluctuating between a neutral and a charged state. The LFN level normalized to the square of the DC current in HRS is about two orders of magnitude higher than the corresponding value for LRS. The higher normalized LFN observed in HRS is ascribed to the smaller cross-section area of the conductive filament and to the stronger effect of the potential barrier modulation induced by a trapped electron. The normalized LFN is independent of the temperature for both resistance states as well as of the bias voltage in LRS, while it decreases with the bias in HRS, which is well correlated to the corresponding resistance decrease.

Low-frequency noise behavior of junctionless transistors compared to inversion-mode transistors

Low-frequency (LF) noise characteristics of wide planar junctionless transistors (JLTs) are investigated. Interestingly, carrier number fluctuation is the main contributor to the LF noise behavior of JLT devices, even though their bulk conduction features are clearly proved by the extracted flat-band voltage (Vfb). This is explained by the fact that mobile electrons in depletion, originating from the bulk neutral channel or source/drain regions, can interact with slow traps in the gate oxide, giving rise in return to fluctuations of the charge density in the bulk neutral channel. Similar values of trap density (Nt) are extracted in JLT devices and inversion-mode (IM) t0072ansistors, which also supports that the LF noise of JLT is well explained by the carrier number fluctuation model.

A Physics-Based Analytical $\hbox{1}/f$ Noise Model for RESURF LDMOS Transistors

A physics-based model has been implemented to describe the low-frequency noise behavior in differently processed reduced-surface-field lateral double-diffused MOS devices. The developed model is based upon the correlated carrier number and the mobility fluctuation theory known as the unified model but has been modified to account for the fluctuations in the extended drain and the channel. Unlike the unified 1/f noise model, nonuniform trap distribution has been taken into account with respect to position in the gate oxide and band-gap energy. The effect of stress on dc and noise characteristics has been investigated. Individual resistance and noise components in the channel and in the extended drain regions under the gate and field oxides are evaluated as a function of stress duration. The model is experimentally verified to identify the physical mechanisms for degradation due to stressing.

Low-Frequency Noise Studies on Fully Depleted UTBOX Silicon-on-Insulator nMOSFETs: Challenges and Opportunities

The low-frequency (LF) noise behavior of Fully Depleted (FD) Ultra-Thin Buried Oxide (UTBOX) Silicon-on-Insulator (SOI) nMOSFETs is described from the perspective of the three major noise sources: 1/f-like or flicker noise, associated with carrier trapping/detrapping in the gate oxide; Generation-Recombination (GR) noise due to processing-induced defects in the thin silicon film and single-oxide-trap-related Random Telegraph Noise (RTN). It is shown that the fully depleted nature of the thin silicon films (<20 nm) offers the unique opportunity to study and demonstrate the front-back coupling of the 1/f noise. At the same time, a large variability is induced in the noise power spectral density by the presence of Lorentzian noise, related with GR events through defects in the silicon film. A method to discriminate oxide- from film-defects-related Lorentzian noise is pointed out. Finally, the implications for future fully depleted fin-type of devices will also be addressed.

Investigation of Low-Frequency Noise Behavior After Hot-Carrier Stress in an n-Channel Junctionless Nanowire MOSFET

The dc performance and low-frequency (LF) noise behaviors after hot-carrier (HC)-induced stress were compared for a junctionless nanowire transistor (JNT) and an inversion-mode nanowire transistor (INT). Less dc degradation was found in the JNT than in the INT. Due to the low lateral peak electric field (E-field) and electrons traveling through the center of the nanowire, the LF noise increment after HC-induced stress in the JNT is much lower than that in the INT. Furthermore, due to the higher lateral peak E-field located under the gate and the conduction path that occurs near the surface, the LF noise of the INT is very sensitive to HC stress.

$\hbox{1}/f$ Noise in 45-nm RESET-State Phase-Change Memory Devices: Characterization, Impact on Memory Readout Operation, and Scaling Perspectives

In this letter, we study the low-frequency noise behavior of RESET-state Phase-Change Memory (PCM) devices belonging to a 45-nm technology node. Furthermore, by dealing with a typical case study, we calculate the fluctuation of the cell readout current induced by <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{1}/f$</tex></formula> noise and provide predictions for estimating its effect in RESET-state PCM of future technology nodes.

Investigation of the Low-Frequency Noise Behavior and Its Correlation with the Subgap Density of States and Bias-Induced Instabilities in Amorphous InGaZnO Thin-Film Transistors with Various Oxygen Flow Rates

The low-frequency noise (LFN) behavior and its correlation with the subgap density of states (DOSs) and bias-induced instabilities are investigated in the amorphous indium–gallium–zinc–oxide (a-IGZO) thin-film transistors (TFTs) with various oxygen flow rates. Higher LFN is measured in the higher oxygen flow rate devices in the subthreshold regime, which is attributed to the increased trapping/release processes. We also obtain higher subgap DOSs and larger threshold voltage shifts under positive bias stresses in higher oxygen flow rate devices, which represents that the LFN measured in the subthreshold regime is deeply correlated with the subgap DOSs and electrical instabilities in a-IGZO TFTs.

Investigation of the Low-Frequency Noise Behavior and Its Correlation with the Subgap Density of States and Bias-Induced Instabilities in Amorphous InGaZnO Thin-Film Transistors with Various Oxygen Flow Rates

The low-frequency noise (LFN) behavior and its correlation with the subgap density of states (DOSs) and bias-induced instabilities are investigated in the amorphous indium–gallium–zinc–oxide (a-IGZO) thin-film transistors (TFTs) with various oxygen flow rates. Higher LFN is measured in the higher oxygen flow rate devices in the subthreshold regime, which is attributed to the increased trapping/release processes. We also obtain higher subgap DOSs and larger threshold voltage shifts under positive bias stresses in higher oxygen flow rate devices, which represents that the LFN measured in the subthreshold regime is deeply correlated with the subgap DOSs and electrical instabilities in a-IGZO TFTs.

Low Frequency Noise in 4H-SiC Lateral JFET Structures

Low frequency noise on 4H-SiC low-level signal-lateral JFETs was systematically investigated. In contrast to previous studies, which are based upon high power vertical structures, this work investigates the low-frequency noise behaviour of low-level signal-lateral devices which are more relevant to the realisation of small signal amplifiers.The JFETs studied share an identical cross section, with different gate lengths and widths. For high temperature operation between 300K and 700K at VGS = 0V, the Normalised Power Spectral Density (NPSD) of the JFETs is proportional to ƒ-1. The NPSD increases monotonically with temperature until a critical temperature, where it starts to decline. Two unique noise origins, fluctuation from bulk and SiO2-SiC interface traps were observed across all the devices investigated. Low frequency noise for devices with a 50μm gate width is localised at the SiO2-SiC interface, whereas for wider devices the noise is seen to be of bulk/substrate origin, which follows Hooge’s model.

Advantages of Silicon Nanowire Metal–Oxide–Semiconductor Field-Effect Transistors over Planar Ones in Noise Properties

We have investigated the low-frequency noise behavior of silicon nanowire metal–oxide–semiconductor field-effect transistors (NWFETs) by comparison with that of a planar FET. We have found that the NWFET exhibits lower noise intensity than the planar FET. By analyzing the factors influential to noise intensity, one of the most possible origins of this advantage of the NWFET results from the electron distribution in the channel in NWFET. Owing to quantum confinement, the position of charge-centroids in the channel of NWFET is located further from the interface, resulting in the lower trapping probability between the electrons and oxide traps. These results clearly demonstrate the advantage of three-dimensional structures in static and noise properties.

Area Dependent Low Frequency Noise in Metal Oxide Based Resistive Random Access Memory

Metal oxide based resistance random access memory (RRAM) has been extensively studied as one of the most promising candidate for next generation nonvolatile memory; however the current conduction mechanism is not yet clearly understood. To tackle this problem, low frequency noise behavior in metal oxide based RRAM device has been investigated in this work. Together with DC current voltage characteristics, it confirms that for the low resistance state, current conduction is localized without an area dependence, whereas, for the high resistance state, it is a uniform leakage current throughout the whole device area. This is consistent with the filament type resistive switching phenomenon in such devices.

Crystal Quality Effect on Low-Frequency Noise in ZnO TFTs

The effect of ZnO active film quality on the low-frequency noise behavior in ZnO thin-film transistors has been investigated. The film crystalline is varied by differentiating the thickness and adding postannealing. To discriminate the origin of 1/f noise, the gate bias dependence of noise spectra is investigated. It is found that the number fluctuation noise model related with trapping/detrapping by traps near the interface becomes dominant as the crystal quality improves, which is also confirmed by another noise parameter, i.e., α Extracted αapp can also well explain the electrical characteristics.