Noise Voltage Spectral Density Research Articles

1$/f$ Noise of Sb-Heterostructure Diodes for Pre-Amplified Detection

The 1/f noise of a series of Sb-heterostructure diodes with varying area has been measured. Standard power law formulas for the frequency and voltage dependence were found adequate to summarize the data. An inverse dependence of voltage noise spectral density on the area was determined, consistent with the simple resistor model. Simulations using the noise formula predict that pre-amplification gain in the 30 to 35 db range can produce a sub-1degK noise equivalent temperature difference in realistic imaging cameras

Impact of the gate-electrode/dielectric interface on the low-frequency noise of thin gate oxide n-channel metal-oxide-semiconductor field-effect transistors

The low-frequency (LF) noise of n-MOSFETs with a 1.5 nm SiON gate oxide is studied for different gate materials, namely, a polycrystalline (poly) silicon gate, a fully nickelsilicided (FUSI) gate and a NiSi FUSI gate deposited on 10 cycles of HfO 2. The principal aim is to identify the most likely origin of the predominant 1/ f noise in the thin gate oxide devices by investigating the impact of the gate electrode processing. It is reported that the lowest input-referred voltage noise spectral density ( S VG) in linear operation for a gate voltage at the threshold voltage is found for the FUSI transistor, while adding 10 cycles of HfO 2 enhances markedly the noise magnitude. The 1/ f noise characteristic behaves according to the number fluctuations theory so that the results are interpreted in terms of trapping and de-trapping of channel carriers by defects in the gate dielectric layer. Therefore, the marked effect of the gate material is at present ascribed to the different trap density in the vicinity of the gate-SiON interface, which is derived from the LF noise spectra.

NOISE MEASUREMENTS ON NbN THIN FILMS WITH A NEGATIVE TEMPERATURE RESISTANCE COEFFICIENT DEPOSITED ON SAPPHIRE AND ON SiO2

We characterize granular NbN x thin cermet films deposited on either sapphire substrate or on SiO 2 and compare the 1/f noise at 300 K and 80 K. The films were characterized with an impedance analyzer from 20 Hz to 1 MHz and analyzed as a resistor R in parallel with a capacitor C. The calculated noise voltage spectral density SvTh of the sample is in agreement with the experimentally observed noise for unbiased samples. The noise measurements on biased samples show 1/f noise. We checked that contact noise does not contribute to our measurements. The 1/f noise was compared for the films deposited on the silicon substrate and on the sapphire. Finally a model is proposed to explain the observed trends in the temperature resistance coefficient (TRC < 0 for all samples) and the relative 1/f noise at 300 K and 80 K with the composition x = N/Nb of the layers.

Low-frequency noise measurements of high-Tc superconducting films: effect of DC capacitor in experimental setup

Often a transformer is used with a DC-blocking capacitor as a voltage gain stage in experimental setups that measure low-frequency noise in high-Tc superconducting films. Presented is a system response analysis to show that the value of the DC-blocking capacitor determines the validity of the lower frequency limit of the measured noise voltage spectral density data.

Dynamic of vortices in YBa2Cu3O7–δ single crystal near the temperature of the vortex glass transition by the use of voltage noise measurements

AbstractWe have studied the voltage noise Vn and the voltage noise spectral density SV of YBa2Cu3O7–δ superconductor in the regime of high magnetic field. Our studies were performed in a large range of temperature T (70 K‐90 K) covering the vortex‐glass ‐ vortex‐liquid transition which appears at Tg temperature. The sample is driving by a current I = 1 nA, under a different high magnetic fields H (2.4 T, and 5 T). The noise spectral density noted SV(f) exhibits a 1/fα. Approaching Tg the vortex glass transition, the voltage noise spectral density SV(T) is found to vanish critically according to the critical power law SV ∝ (T‐Tg)x, with x = 1.64 ± 0.1 which represents the critical exponent. The behaviour exhibited by Sv(T) cannot be simply interpreted by thermal fluctuations as we conclude by comparing SV(T) with (dR/dT)2 curve. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Measurements and analysis of the noise spectral density of YBCO films

AbstractWe studied the voltage noise spectral density S V(f, T, H ) dependence on frequency f, temperature T and applied magnetic field H in YBa2Cu3O7–δ films. The voltage noise spectral density S V(f ) as a function of frequency exhibits 1/f behavior according to a Lorentzian shape A [(1 + πf /f 0)B ]C, where A, f 0, B, C constants which are determined and compared for many values of H . The influence of temperature and magnetic field is clearly observed as a function of temperature, S V(T ) is found to vanish at T g, the temperature of vortex glass transition, according to a (T – T g)x law. We interpreted those results by the formation of a large distribution of glass vortex domains. Approaching T g, these domains grow in size and lifetime, while at T g those parameters diverge. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Measurement of Low-Frequency Noise of Modern Low-Noise Junction Field Effect Transistors

A description of the low-noise measurement system designed for experimental investigation of low-frequency noise of modern low-noise junction field effect transistors (JFETs) at a frequency range from 0.5 Hz to 50 kHz is presented. The noise floor of the system in terms of noise voltage spectral density is about 1.3 nV//spl radic/Hz at frequency 0.5 Hz, 0.6 nV//spl radic/Hz at frequency 1 Hz, 0.08 nV//spl radic/Hz at frequency 10 Hz, and /spl les/0.04 nV//spl radic/Hz at frequencies 100 Hz-50 kHz. Such a system makes it possible to measure 1/f noise and channel thermal noise of modern very low noise n-channel JFETs. Specifically, discrete samples of JFETs, IF9030, IF1801, IF3601, and 2N4338, were investigated at the frequency range mentioned above. The system provided negligible contribution of all noise sources except intrinsic noise of measured JFETs which was a 1/f noise at frequencies f < 10 Hz and a channel thermal noise at frequencies f /spl ges/ 10 Hz. The measured values of the equivalent input noise voltage spectral density e/sub n/ of the best samples from investigated JFETs IF9030, IF1801, IF3601, and 2N4338 were 2.7, 3.2, 3.4, and 22 nV//spl radic/Hz at frequency 0.5 Hz; 1.5, 2.1, 1.8, and 14 nV//spl radic/Hz at frequency 1 Hz; and 0.5, 0.4, 0.6, and 3.2 nV//spl radic/Hz at frequencies more than 1 kHz, correspondingly.

Design of a low-power 3.5-GHz broad-band CMOS transimpedance amplifier for optical transceivers

This paper describes a novel low-power low-noise CMOS voltage-current feedback transimpedance amplifier design using a low-cost Agilent 0.5-/spl mu/m 3M1P CMOS process technology. Theoretical foundations for this transimpedance amplifier by way of gain, bandwidth and noise analysis are developed. The bandwidth of the amplifier was extended using the inductive peaking technique, and, simulation results indicated a -3-dB bandwidth of 3.5 GHz with a transimpedance gain of /spl ap/60 dBohms. The dynamic range of the amplifier was wide enough to enable an output peak-to-peak voltage swing of around 400 mV for a test input current swing of 100 /spl mu/A. The output noise voltage spectral density was 12 nV//spl radic/Hz (with a peak of /spl ap/25 nV//spl radic/Hz), while the input-referred noise current spectral density was below 20 pA//spl radic/Hz within the amplifier frequency band. The amplifier consumes only around 5 mA from a 3.3-V power supply. A test chip implementing the transimpedance amplifier was also fabricated using the low-cost CMOS process.

Low field magnetoresistance and conduction noise in layered manganite La 1.4Ca 1.6Mn 2O 7

Temperature dependence of conduction noise and low field magnetoresistance of layered manganite La 1.4Ca 1.6Mn 2O 7 (DLCMO) are reported and compared with the infinite layered manganite La 0.7Ca 0.3MnO 3 (LCMO). The double layered manganite was prepared using standard solid state reaction method and had a metal–insulator transition temperature ( T M–I) of 155 K. The temperature dependence of susceptibility showed evolution of ferromagnetic ordering at 168 K. The observed voltage noise spectral density ( S V ) shows 1/ f α type of behaviour at all temperatures from 77 K to 300 K. In the ferromagnetic region ( T<168 K), S V / V 2 shows two peaks at 164 K and 114 K. The observed two peaks in normalised conduction noise of DLCMO is attributed to the excess noise generated due to setting up of short range 2D-ferromagnetic ordering and long range 3D-ferromagnetic ordering at two different temperatures T C2 and T C1. In temperature range between T C1 and T C2, the magnetoresistance (MR) showed a gradual increase with the magnetic field. The observed MR has been explained in the framework of the two phase model [ferromagnetic (FM) domains and paramagnetic (PM) regions].

The Effect of LAC Doping on Deep Submicrometer Transistor Capacitances and its Influence on Device RF Performance

In this paper, we have systematically investigated the effect of lateral asymmetric doping on the MOS transistor capacitances and compared their values with conventional (CON) MOSFETs. Our results show that, in lateral asymmetric channel (LAC) MOSFETs, there is nearly a 10% total gate capacitance reduction in the saturation region at the 100-nm technology node. We also show that this reduction in the gate capacitance contributes toward improvement in f/sub T/, f/sub max/, and RF current gain, along with an improved transconductance in these devices. Our results also show that reduced short-channel effects in LAC devices improve the RF power gain. Finally, we report that the lateral asymmetric channel doping gives rise to a lower drain voltage noise spectral density compared to CON devices, due to the more uniform electric field and electron velocity distributions in the channel.

Thermal Magnetic Noise in Tunneling Readers

We present modeling results, using the stochastic Landau-Lifshitz-Gilbert approach, of thermal magnetic noise in TMR sensors of dimensions suitable for 100-150 Gbit/in/sup 2/. In particular, we have investigated the effect of aspect ratio and permanent-magnet bias on the thermally induced magnetization fluctuations as well as the induced noise voltage spectral density. We show that there can be a lower frequency resonance due to the motion in the reference layer of the tunneling magnetoresistance reader, uncorrelated with the motion of the free layer, which gives rise to a structure in the noise voltage spectral density. We also present measured noise spectra which exhibit similar characteristics with a well defined resonance peak and a smaller peak at a lower frequency, which we attribute to resonance motion in the reference layer. The motions of the free and reference layers are greatly influenced by the strength of the bias field from the permanent magnets. For example, too low bias field may give rise to increased low-frequency noise due to switching behavior in the pinned and reference layers.

Impact of the high vertical electric field on low-frequency noise in thin-gate oxide MOSFETs

In this paper, quantum effects induced by the high vertical electric field, i.e., inversion layer quantization and gate current tunneling, are taken into account to model the low-frequency noise behavior of 0.13 /spl mu/m technology node thin gate oxide MOSFETs. First, we show that the modifications induced by inversion layer quantization in the band structure and spatial distribution of the inversion layer carriers must be taken into account when extracting an effective density of traps from 1/f noise measurements. The ultrathin gate oxide and the high substrate doping of scaled MOSFETs create a strong electrical field in the inversion layer, which causes the surface conduction (n-) or valence (p-MOSFET) band to split into discrete energy levels. The first allowed state resides then above (below) the conduction (valence) band level in the bulk, giving rise to a band gap widening and in addition the spatially localized charge centroid is at a finite distance from the SiO/sub 2//Si interface. The impact on both dc and noise parameters of these quantum effects have been numerically calculated and compared to experimental results. The main conclusions coming out of this study is that if the inversion layer quantization is neglected, inaccurate oxide trap densities will be derived from the input-referred voltage noise spectral density S/sub VC/:. A similar conclusion will hold for the extraction of the scattering coefficient derived in the frame of a correlated number fluctuations model or for the effective Hooge parameter, derived from the normalized drain current spectral density S/sub ID//I/sub D//sup 2/. Finally, a particular gate tunneling mechanism namely Electron Valence Band (EVB) tunneling is shown to modify the noise behavior of thin gate oxide devices in terms of a self-biasing body effect.

Design of a low-noise preamplifier for nerve cuff electrode recording

This paper discusses certain important issues involved in the design of a nerve signal preamplifier for implantable neuroprostheses. Since the electroneurogram signal measured from cuff electrodes is typically on the order of 1 /spl mu/V, a very low-noise interface is essential. We present the argument for the use of BiCMOS technology in this application and then describe the design and evaluation of a complete preamplifier fabricated in a 0.8-/spl mu/m double-metal double-poly process. The preamplifier has a nominal voltage gain of 100, a bandwidth of 15 kHz, and a measured equivalent input-referred noise voltage spectral density of 3.3 nV//spl radic/Hz at 1 kHz. The total input-referred rms noise voltage in a bandwidth 1 Hz-10 kHz is 290 nV, the power consumption is 1.3 mW from /spl plusmn/2.5-V power supplies, and the active area is 0.3 mm/sup 2/.

Full-frequency voltage noise spectral density of a single-electron transistor

We calculate the full frequency spectral density of voltage fluctuations in a Single Electron Transistor (SET), used as an electrometer biased above the Coulomb threshold so that the current through the SET is carried by sequential tunnel events. We consider both a normal state SET and a superconducting SET. The whole spectrum from low frequency telegraph noise to quantum noise at frequencies comparable to the SET charging energy $(E_{C}/\hbar)$, and high frequency Nyquist noise is described. We take the energy exchange between the SET and the measured system into account using a real-time diagrammatic Keldysh technique. The voltage fluctuations determine the back-action of the SET onto the measured system and we specifically discuss the case of superconducting charge qubit read-out and measuring the so-called Coulomb staircase of a single Cooper pair box.

Conduction noise in La0.67Ca0.33MnO3 film

The temperature and frequency dependence of conduction noise in La0.67Ca0.33MnO3 film are reported. The film was prepared by a screen printing technique and had a metal–insulator transition temperature (Tp) and ferromagnetic transition temperature (TC) at 140 and 230 K, respectively. The magnetoresistance ratio (MRR) of the film at 1 kOe was found to be mainly due to grain boundaries. The observed voltage noise spectral density (Sv) shows 1/fα type behavior for all the temperatures ranging from 77 to 300 K. Sv shows an increase as the temperature is decreased below TC and reaches a peak value at Tp. The increase in Sv below TC is attributed to extra noise arising due to fluctuations in spin alignment in the ferromagnetic state. Application of a 1 kOe magnetic field reduces noise and the reduction in the noise is observed up to TC. A comparison of the temperature dependence of MRR and noise reduction ratio due to the magnetic field indicates that the magnetoresistance in the polycrystalline film of La0.67Ca0.33MnO3 is strongly influenced by the grain boundaries but the noise due to fluctuations in spin alignment is intrinsic and comes mainly from the grains.

LOW FREQUENCY NOISE CONVERSION IN FETS UNDER NONLINEAR OPERATION

The conversion mechanisms of microscopic low frequency noise sources (e.g. generation-recombination noise sources) located in the channel of a FET (Field Effect Transistor), in the presence of a large RF signal, are investigated. It is shown that the base-band (low frequency) input gate noise voltage spectral density is strongly dependent on the magnitude of the input RF power applied to the FET. Moreover, the microscopic generation-recombination noise sources distributed along the channel are also responsible of up-converted input gate noise voltage spectral density around the RF frequency.

Current-induced voltage noise below the Kosterlitz–Thouless transition

We have measured the current–voltage ( I– V) characteristics and voltage–noise spectral density S V ( f ) for very thin amorphous Mo x Si 1− x films far below the Kosterlitz–Thouless transition temperature. The large 1/ f-like noise is observed over broad frequencies f in a current range where the I– V curve shows a strong nonlinearity. The noise spectra, S V ( f )/V (divided by V), for different I show a trend to collapse onto a single line of 1/f β ( β≈0.75) at high f. The characteristic frequency f C below which S V ( f )/V deviates downward from the 1/f β line increases rapidly with increasing I. The observed noise cannot be explained by the simple shot noise model of vortices.

Noise of the JFET amplifier

By analyzing the different noise sources of the silicon JFET amplifier, engineering formulae for equivalent noise voltage referred to the input of the JFET amplifier are derived. Formulae are obtained for common signal source impedance and particularly for capacitance-type signal source impedance. If the parameters of the JFET, the signal source, and the load are known, these formulae can he used to estimate the overall noise of the JFET amplifier over a wide frequency band. The theoretical curve of the overall equivalent noise voltage spectral density at frequencies from 0.5 Hz to 50 kHz has good correlation to a measured experimental curve. The contribution of the different noise sources to the overall noise is shown. For modern low-noise JFET's, 1/f noise prevails over the channel thermal noise at frequencies f/spl les/100 Hz. When using high-capacitance-type signal source impedance, contribution of the biasing resistor thermal noise to the overall noise predominates at low frequencies f/spl ges/1 kHz and room temperature. At upper frequencies f/spl ges/1 kHz, overall noise is due mainly to the JFET's thermal channel noise.

Estimation of the noise temperature of YBaCuO grain boundary Josephson junctions

Abstract We examine the extent to which low-frequency critical current fluctuations contribute to increased noise temperatures in HTS grain boundary junctions. The effective Josephson linewidth is first estimated (a) by fitting of the noise-rounded DC I ( V ) characteristic, and (b) by fitting of the noise-rounded Shapiro steps. The expected linewidth due to the contribution of the low-frequency voltage noise spectral density is then calculated. Values of noise temperature T n ∼ 170 ± 10 K as found by the three methods are mutually consistent, indicating that the low-frequency noise is indeed responsible for the observed noise temperatures. This result is not inconsistent with previous measurements of the linewidth of the Josephson radiation, when the bandwidth of the measurement system is taken into account. Implications of these results for the reliability of HTS grain-boundary junctions in metrology applications such as Josephson noise thermometry are discussed.

Estimation of the noise temperature of YBaCuO grain boundary Josephson junctions

We examine the extent to which low-frequency critical current fluctuations contribute to increased noise temperatures in HTS grain boundary junctions. The effective Josephson linewidth is first estimated (a) by fitting of the noise-rounded DC I( V) characteristic, and (b) by fitting of the noise-rounded Shapiro steps. The expected linewidth due to the contribution of the low-frequency voltage noise spectral density is then calculated. Values of noise temperature T n ∼ 170 ± 10 K as found by the three methods are mutually consistent, indicating that the low-frequency noise is indeed responsible for the observed noise temperatures. This result is not inconsistent with previous measurements of the linewidth of the Josephson radiation, when the bandwidth of the measurement system is taken into account. Implications of these results for the reliability of HTS grain-boundary junctions in metrology applications such as Josephson noise thermometry are discussed.