Flicker noise in ion-implanted silicon structures

Low-frequency (flicker) noise is one of the most important issues in the design of direct-conversion zero-IF front-ends. Within the front-end building blocks, the direct-conversion mixer is critical in terms of flicker noise, since it performs the signal down-conversion to baseband. This paper analyzes the main sources of low-frequency noise in Gilbert-cell-based direct-conversion mixers, and several issues for minimizing the flicker noise while keeping a good mixer performance in terms of gain, noise figure and power consumption are introduced in a quantitative manner. In order to verify these issues, a CMOS Gilbert-cell-based zero-IF mixer has been fabricated and measured. A flicker noise as low as 10.4 dB is achieved (NF at 10 kHz) with a power consumption of only 2 mA from a 2.7 V power supply. More than 14.6 dB conversion gain and noise figure lower than 9 dB (DSB) are obtained from DC to 2.5 GHz with an LO power of -10 dBm, which makes this mixer suitable for a multi-standard low-power zero-IF front-end. Copyright © 2008 John Wiley & Sons, Ltd.

The concurrent effect of fluorine implantation with various energy and dose on reliability and low-frequency noise characteristics of p-MOSFETs was investigated. The <inline-formula> <tex-math notation="LaTeX">$\Delta $ </tex-math></inline-formula>VT degradation that represents device lifetime of p-MOSFETs with fluorine implantation under negative-bias temperature instability stress was less than that without fluorine implantation. The device lifetimes were improved as the fluorine implantation energy and dose increase. The power law exponent <inline-formula> <tex-math notation="LaTeX">$n $ </tex-math></inline-formula>with the fluorine implantation was larger than that without fluorine implantation. This was related to boron diffusion within the gate oxide because the F atoms enhance the diffusivity of the boron. The difference of flicker noise levels between simulation and measurement data at 1 kHz was much greater than that at 10 Hz, which means that F atoms were mainly located near the Si/SiO₂ interface rather than in the bulk oxide. The fluorine implantation reduced the ID-RTS noise amplitude, which was believed to contribute to the effective passivation of the dominant traps within the gate oxide. Also, the flicker noise was less dependent on implantation energy. But, flicker noise was reduced with increasing implantation dose. Therefore, fluorine implantation is potentially significant for reducing low-frequency noise as well as improving reliability characteristics.

The total input noise current and sensitivity of the fiber-optic receiver was calculated. The flicker noise source was included by adopting a pertinent flicker noise model. Power penalties caused by the flicker noise were calculated for various fiber-optic receivers using the calculated noise current. It has been found that the flicker noise affects the sensitivity over the whole range of the bit rates, and that the total input capacitance is an important parameter affecting the power penalty which is serious in the case of a high-impedance-type p-i-n FET receiver. The optimum feedback resistance for practical p-i-n FET receiver design is also suggested.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

In organic thin-film transistors (OTFTs) the intrinsic properties of the semiconductor are generally masked by structural defects which localize and trap the charge carriers and contact effects, which limit charge injection and cause deviation from ideal linear and square-law behavior. Thus, their electrical characteristics are strongly dependent on the fabrication conditions. We perform current-voltage (I-V) and low frequency noise (1/f) measurements to demonstrate a direct correlation between the thin film microstructure and the performance of OTFTs. Using fluorinated 5,ll-bis(triethylsilylethynyl) anthradithiophene as a model system, we show the relevance of the grain size and grain distribution in the changes in the electronic properties in an OTFT. We present a simple method to induce enhanced grain growth in solution-processed TFTs by room-temperature chemical modification of the source-drain contacts. This leads to improved device performance, and gives an unique thin film microstructure for fundamental studies concerning the effect of structural order on the charge transport. We present evidence that the 1/f flicker noise is sensitive to the microstructure of the organic semiconductor thin film in the transistor channel and can be a diagnostic tool for the quality of the devices.

This letter presents measurement results and an analysis of an input-signal dependent flicker noise modulation in chopper stabilized current balancing instrumentation amplifier. Although the chopping is well known and often used for its effectiveness in flicker noise mitigation, measurement results show an increased effect of the 1/f noise proportional to input signal amplitude. This effect is often ignored in most publications and will also not be apparent in traditional noise measurements (due to the lack of input signal when doing noise measurements). The unexpected operation was confirmed by a Spectre simulation and the main cause can be attributed to a flicker noise modulation by input signals of large amplitude. Because of the signal-dependency of the effect, flicker noise remains (and can be significant) even when chopping is applied.

Several flicker-noise models, such as the island model which ascribes flicker noise to the charge fluctuations of defects, obtain a 1/${f}^{\ensuremath{\gamma}}$ spectrum, with \ensuremath{\gamma}\ensuremath{\simeq}1, from the superimposition of Lorentzian spectra proportional to the relaxation time \ensuremath{\tau} of the process being considered, weighted by the distribution ${D}_{\ensuremath{\tau}}$ of \ensuremath{\tau}. Here it is shown, rather, that the Lorentzian power spectral density of the charge fluctuation of single-energy-level defects, characterized by both tunnel and thermally activated emission, is proportional to ${\ensuremath{\tau}}^{1+\ensuremath{\nu}}$, with \ensuremath{\nu}&gt;0. Indeed, this result implies that, in the previous superimposition, the equivalent distribution ${D}_{\ensuremath{\tau}e}$\ensuremath{\propto}${\ensuremath{\tau}}^{\ensuremath{\nu}}$${D}_{\ensuremath{\tau}}$ of \ensuremath{\tau} has really to be used instead of ${D}_{\ensuremath{\tau}}$. In relation to the case of ${D}_{\ensuremath{\tau}}$ and \ensuremath{\nu}=0, such a change leads to an increase in the weight of the greater \ensuremath{\tau}'s, to a shift of the eventual maxima of ${D}_{\ensuremath{\tau}}$ towards the greater values of \ensuremath{\tau}, to a considerable increase in the effective number of defects (with dispersed \ensuremath{\tau}) which are able to generate 1/${f}^{\ensuremath{\gamma}}$ noise with \ensuremath{\gamma}\ensuremath{\simeq}1, and accordingly, to a satisfactory and simple explanation of the ubiquity and existence of flicker noise down to however low frequency f, as is found experimentally. In particular, for thermally activated emission for which we have \ensuremath{\nu}=1, the new model, as compared with the previous ones characterized by \ensuremath{\nu}=0, leads to a much smaller value of the activation energy obtained by means of 1/${f}^{\ensuremath{\gamma}}$ noise measurements. A new general method for computing the local frequency exponent \ensuremath{\gamma}(f) of the spectrum is also described. The theoretical results obtained from the new approach closely agree with the experimental findings concerning metal-film and thick-film resistors.

Surface diffusion model of adsorption-induced field emission flicker noise: II. Experiments

Measurements of the frequency and temperature dependence of the noise spectrum and of its frequency exponent have been performed on thick-film resistors and, together with the direct plots versus the frequency logarithm of the spectrum-frequency product, they are used to check the island model of the flicker noise. It is shown that the wide dispersion of the island relaxation times, necessary to originate the flicker noise, is due to tunnel emission and/or thermal activation processes of electrons from localized states, and to the exponential dependence of their emission probability on random variable distances and activation energies, whose distribution functions, means, and variances are determined both theoretically and experimentally. I. PREMISE The island model of the low-frequency excess noises' shows that these phenomena, including the flicker noise, are generated by localized states, called islands, that exchange charge carriers with the surrounding conductive medium through tunnel emission and/or thermal activation processes. This latter type of process leads to a strong temperature dependence of the conductance 6 of the islands and of their relaxation times r Further. more, the model predicts that the product fSy(f, T) between the frequency f and the power spectral density Sq of the voltage fluctuations is related to the distribution function D of the logarithm of 6, calculated at — ln(f /f„), by the relationship fSv(f, T)= ((b V)~ ),D( — ln(f/f„) ), where ((AV) ), is the variance of the voltage fluctuations, f„ is a reference frequency, and T is the temperature. Consequently, a careful analysis of measured data of fSv vs ln(f/f„) over wide frequency and temperature ranges should be able to give interesting physical information of the investigated system and, together with a detailed model of the distribution function of the island conductance logarithm, should allow us to check quite easily the validity of the island theory of the flicker noise. In this paper we will show that both these goals have been attained by means of the study of the excess noise in thick-film resistors and of a measuring system that includes a digital signal analyzer that

The noise current spectral density of an a-Si:H pin diode can be calculated with experimentally determined flicker noise coefficients by superposition of the shot and flicker noise spectra of photocurrent and dark current. The dependence of the flicker noise current spectral density in pin diodes on the pixel area is calculated with our expansion of Hooge's law for flicker noise. We propose a new method for the calculation of dynamic range (DR) and signal-to-noise ratio (SNR) in pin diode pixels as a function of pixel area, dark current, photocurrent and the integration time of the imager. DR and SNR of the pin diodes are calculated for Thin Film on ASIC (TFA) image sensors.

Impact of forward and reverse deep n-well biasing on the 1/f noise of 0.13 μm n-channel MOSFETs in triple well technology

The low-frequency noise in a nanometer-sized virtual memristor consisting of a contact of a conductive atomic force microscope (CAFM) probe to an yttria stabilized zirconia (YSZ) thin film deposited on a conductive substrate is investigated. YSZ is a promising material for the memristor application since it is featured by high oxygen ion mobility, and the oxygen vacancy concentration in YSZ can be controlled by varying the molar fraction of the stabilizing yttrium oxide. Due to the low diameter of the CAFM probe contact to the YSZ film (∼10 nm), we are able to measure the electric current flowing through an individual filament both in the low resistive state (LRS) and in the high resistive state (HRS) of the memristor. Probability density functions (Pdfs) and spectra of the CAFM probe current in both LRS and HRS are measured. The noise in the HRS is found to be featured by nearly the same Pdf and spectrum as the inner noise of the experimental setup. In the LRS, a flicker noise 1/fγ with γ ≈ 1.3 is observed in the low-frequency band (up to 8 kHz), which is attributed to the motion (drift/diffusion) of oxygen ions via oxygen vacancies in the filament. Activation energies of oxygen ion motion determined from the flicker noise spectra are distributed in the range of [0.52; 0.68] eV at 300 K. Knowing these values is of key importance for understanding the mechanisms of the resistive switching in YSZ based memristors as well as for the numerical simulations of memristor devices.

A short review of theoretical and experimental results concerning flicker noise in small metallic structures with a special emphasis on telegraph noise related to separate ‘‘fluctuators.’’ It is demonstrated that the behavior observed including temperature, bias, and magnetic field behavior can be explained within a framework of the model of ‘‘soft’’ double‐well interatomic potentials. The applications to superconducting state (including high‐Tc materials are discussed.

On the design of ultra low noise amplifiers for eng recording Due to the extremely low amplitude of the input signals, the design of electro-neurgo-graph (ENG) amplifiers normally involves special care for flicker and thermal noise reduction. The task becomes really challenging in the case of implantable devices, because power consumption is restricted to few tens µW. In this paper, two different circuit techniques aimed to reduce flicker and thermal noise, in ultra-low noise amplifiers for implantable electronics are demonstrated. In both cases circuit design and measurement results are presented, showing an excellent performance in circuit simplicity, and noise to power consumption trade-off. The first circuit is a very simple Gm-C chopper low-pass amplifier for flicker noise cancellation. It consumes only 28mW, with a measured input referred noise and offset of 1.2 nV Hz , and 2.5µV, respectively. For the reduction of thermal noise with minimum power consumption, in the second circuit, a ultra-low noise amplifier, a energy-efficient DC-DC downconverter, and low voltage design techniques are combined. Measured input referred noise in this case was 5,5 nV Hz at only 380µW power consumption. Both circuits were fabricated in a 1,5 micron technology

This paper describes the methods and results of resistance noise spectroscopy applied to SnO/sub 2/ nanoparticle thick-film sensors operated at temperatures of 200, 300, 400, and 500/spl deg/C At each temperature, the sensors were exposed to three hits of 50 ppm of NO, H/sub 2/S, or NH/sub 3/. Sensor noise was sampled before, during, and after each hit. Initial inspection of the results seemed to show unique responses to each gas. More careful analysis revealed that the spectra were shaped by flicker noise, thermal noise, and signal attenuation. Thermal noise and attenuation are primarily functions of sensor DC resistance. Flicker noise was shown to be partly a function of DC resistance, but could not be directly correlated to DC resistance due to other, undetermined parameters.

Improved physics-based analysis to discriminate the flicker noise origin at very low temperature and drain voltage polarization