This PDF file contains the front matter associated with SPIE Proceedings Volume 6600, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

There are three major sources of the 'randomness' underlying noise phenomena. These are the random outcomes of quantum 'measurement' processes, the random ensembles of statistical mechanics, and the algorithmic complexity of many dynamical processes. Here I dwell on the possible connections between the first two sources of randomness. It is often held that the empirical irreversibility of quantum measurement arises from statistical mechanics. I present somewhat speculative arguments that in fact the irreversible approach to statistical ensembles may be rooted in an irreversible quantum decoherence process.

Very recently, it has been shown that Gaussian thermal noise and its artificial versions (Johnson-like noises) can be utilized as an information carrier with peculiar properties therefore it may be proper to call this topic Thermal Noise Informatics. Zero Power (Stealth) Communication, Thermal Noise Driven Computing, and Totally Secure Classical Communication are relevant examples. In this paper, while we will briefly describe the first and the second subjects, we shall focus on the third subject, the secure classical communication via wire. This way of secure telecommunication utilizes the properties of Johnson(-like) noise and those of a simple Kirchhoff's loop. The communicator is unconditionally secure at the conceptual (circuit theoretical) level and this property is (so far) unique in communication systems based on classical physics. The communicator is superior to quantum alternatives in all known aspects, except the need of using a wire. In the idealized system, the eavesdropper can extract zero bit of information without getting uncovered. The scheme is naturally protected against the man-in-the-middle attack. The communication can take place also via currently used power lines or phone (wire) lines and it is not only a point-to-point communication like quantum channels but network-ready. We report that a pair of Kirchhoff-Loop-Johnson(-like)-Noise communicators, which is able to work over variable ranges, was designed and built. Tests have been carried out on a model-line with ranges beyond the ranges of any known direct quantum communication channel and they indicate unrivalled signal fidelity and security performance. This simple device has single-wire secure key generation/sharing rates of 0.1, 1, 10, and 100 bit/second for copper wires with diameters/ranges of 21 mm / 2000 km, 7 mm / 200 km, 2.3 mm / 20 km, and 0.7 mm / 2 km, respectively and it performs with 0.02% raw-bit error rate (99.98 % fidelity). The raw-bit security of this practical system significantly outperforms raw-bit quantum security. Current injection breaking tests show zero bit eavesdropping ability without setting on the alarm signal, therefore no multiple measurements are needed to build an error statistics to detect the eavesdropping as in quantum communication. Wire resistance based breaking tests of Bergou-Scheuer-Yariv type give an upper limit of eavesdropped raw bit ratio is 0.19 % and this limit is inversely proportional to the sixth power of cable diameter. Hao's breaking method yields zero (below measurement resolution) eavesdropping information.

We consider two representative problems that deal with the fluctuator-induced decoherence from two very different perspectives-microscopic and macroscopic. In the first part, we consider an individual two-level system inside a Josephson junction shunted by a resistor. If the TLS modulates the Josephson energy and/or is optically active, it can be Rabi driven by the Josephson oscillation. The Rabi oscillations, in turn, translate into oscillations of current and voltage which can be detected in noise measurements. This effect provides an option to fully characterize the TLS inside Josephson junction and to find the TLS's contribution to the decoherence when the junction is used as a qubit. In the second part, we study the contribution of an ensemble of non-stationary glassy charge fluctuators on qubit decoherence. Low-temperature dynamics of insulating glasses is dominated by a macroscopic concentration of tunneling two-level systems. Due to exponentially broad distribution of their tunneling rates and the finite experimental manipulation timescales, some of the fluctuators are temporarily stuck in high-energy non-thermal states. We find that at low enough temperatures, non-stationary contribution due to these slow non-thermal fluctuators can dominate the stationary (thermal) one, and discuss how this effect can be minimized.

We investigate the shot noise in phase-coherent transport through quantum cavities by a two dimensional ab-initio simulation of the scattering problem. In particular, we study the influence of quantum scattering mechanisms on the transport statistics by tuning the strength of a disorder potential and the openings of the dot. For small cavity openings we find the shot noise for disordered samples to be of almost equal magnitude as for clean samples where transport is ballistic. We explain this finding by diffractive scattering at the cavity openings which act as strong noise sources. For ballistic cavities we demonstrate the emergence of "noiseless scattering states", irrespective of sharp-edged entrance and exit lead mouths. Our numerical results for the onset thresholds of these "classical" states are in very good agreement with analytical estimates.

A deterministic solver for the Langevin Boltzmann equation including the Pauli principle is presented based on a spherical harmonics expansion. The solver can handle rare events, slow processes and low frequencies without problems and without an increase in CPU time in contrast to the Monte Carlo method. This is demonstrated for strongly degenerate systems and deep traps. Although the two electron sub-ensembles for the different spin directions are correlated due to the deep traps, the spin variable can be eliminated without any approximations resulting in a reduction of the number of unknowns by two. Approximations for the inclusion of the Pauli principle are investigated and found to be so bad that it is better to neglect the Pauli principle than to use those approximations.

We have shown that both deterministic and stochastic dynamics of a spatially periodic underdamped system in the presence of, even a rather weak, adiabatic ac-drive drastically differs from that in the absence of the drive or in the presence of other kinds of driving. This suggests promising applications.

We study, using numerical simulations, the transport and noise properties both of a series of barriers and of cascaded constrictions, comparing our results with the conclusions of previous analyses. In particular, we point out the differences existing between the case in which the barriers or the constrictions are evenly spaced and the case in which they are randomly spaced, proposing possible explanations for the observed phenomena.

The effects on the overall device noise of a small number of defects in device sections with a strong transfer impedance coupling to the device terminals is discussed using advanced bulk and silicon-on-insulator n channel MOSFETs and silicon nanowires as examples. From the measured noise and current-voltage data, the precise physical location of the noise centers is determined. Potential noise reduction methods are discussed.

We found quantitative criteria to characterize the states of the device: i) pristine devices show at low bias I proportional to V^m with m = 0 pointing to trap filling and at higher bias m=6 pointing to tunneling. The 1/f noise is characterized by 10^-7 < &agr;&mgr; (cm²/Vs) < 10^-5; ii) forming state is a transition between pristine and switched-state. The time dependent soft breakdown in the Al-oxide goes hand in hand with strong discrete multi level resistive switching (RTS) with a 1/f ^3/2 spectrum. Once the device is switched in the high (H-) or low (L-) conductance state it never comes back to the pristine state. iii) The H- or L-state is characterized by I proportional to V^m with either m = 1 or m = 3/2. The injection model predicts the current level and the dependence of the 1/f noise on current. Reliable switched devices show mainly 1/f noise. In the L-state there is often a 1/f ^3/2 contribution on top of the 1/f noise indicating multi level switching. Reliable switches between the L- and H-state are characterized by a resistance R that changes for example by a factor 30 and the relative 1/f noise, fS_I/I² ≡ C_1/f follows the proportionality: _C1/f proportional to R with a &agr;&mgr;-value of about 3x10^-2 cm²/Vs. The explanation from the noise for C_1/f proportional to R is that the number of carrier in the transport switches due a change of the number of parallel conducting paths in the polymer. The onset of switching seems to be at spots of the Al / Al₂O₃ / polymer interface.

We present an investigation of low-frequency noise in advanced vertical pnp bipolar junction transistors (BJTs) with differing interfacial oxide thicknesses (10Å, 12Å, and 14Å). Low-frequency noise is observed to exhibit a cubic dependence on IFO thickness. Devices were measured across the temperature range of 90 K to 450 K. From 90 K to 250 K, the magnitude of the low-frequency noise is found to decrease with temperature, but from 250 K to 450 K the noise actually increases with temperature. Devices were hot-carrier (electrically) stressed, and the low-frequency noise was found to be almost unchanged with the addition of stress-induced traps. The transparency fluctuation model is suggested as a possible explanation for the operative noise mechanism, due to the similar dependence of base current and low-frequency noise on interfacial oxide thickness.

In this paper we report systematic reliability studies of GaN UV detectors exposed to high power UV radiation. GaN epitaxial layers are deposited by rf plasma-assisted molecular beam epitaxy (MBE) utilizing a double buffer layer structure. Our studies show that the optimal buffer layer structure consists of a conventional AlN high-temperature buffer layer (HTBL) and an 800 nm thick GaN intermediate temperature buffer layer (ITBL) deposited at 690°C. Two types of devices are being investigated. Type I devices were fabricated on the optimal double buffer layer structure. Type II devices have only a conventional AlN buffer layer. Flicker noise measurement is used to monitor the degradation of the device due to optical stress. In addition, I-V and responsivity measurements were also performed. The experimental results are consistent with each other which show that the degradation of the devices arises from the generation of crystalline defects at the Schottky junction due to the exposure of the devices to the high power UV radiation. Both types of devices demonstrate degradation in their optoelectronic properties. However, while type I devices general exhibit gradual and slow degradations type II devices exhibit catastrophic breakdowns in the device characteristics. Our experimental data show that visible-blind UV detectors fabricated on the optimized double buffer layer structure indicate significant improvements in the radiation hardness of the devices.

In this paper we show an approach to couple two stochastic processes to describe the dynamics of independent carriers in semiconductor devices: the launch time of carriers from the contacts is described by independent Poisson launch processes, and the stochastic motion of carriers due to scattering inside the device is described by inhomogeneous Poisson type Markov processes according to the semiclassical transport theory. The coupling of the Poisson type stochastic launch process to the semiclassical dynamics will be shown, and the resulting Ohmic contact boundary conditions will be derived. For proof of concept, an expression for the autocovariance for terminal current noise for one point contact will be shown which can be easily extended to a real semiconductor device with multiple contacts.

The 1/f noise in MOSFETs is stated to be an ensemble of many RTS with different time constants. The majority of literature on 1/f noise is overlooking the contribution due to mobility fluctuations that are uncorrelated with number fluctuations. Our demonstration that the so-called proofs for ΔN can also be obtained from the empirical relation is new. The following misunderstandings and controversial topics will be addressed: 1) 1/f and RTS noise can have different physical origins. An analysis in time domain shows that the low-frequency noise with RTS is nothing else than a superposition of a pure two level noise with a Lorentzian spectrum and a noise with a Gaussian amplitude probability density with a pure 1/f spectrum with different bias dependency and physical origins. 2) It is very unlikely that in a spectrum consisting of one strong two level RTS and a pure 1/f noise, the 1/f noise is a superposition of many RTS with different time constants. 3) The spreading in WLS_I /I² below a critical WL is not a proof for the ΔN origin. 4) The typical shape in the double log plot of S_I /I² versus I, from sub threshold to strong inversion is also not a proof for the ΔN origin.

We have investigated the influence of carbon concentration on the low frequency noise (LFN) of Si/SiGe:C Heterojunction Bipolar Transistors (HBTs). The HBTs are supplied by ST-Microelectronics Crolles and are based on a 0.13 &mgr;m BiCMOS technology. Three types of transistors were studied; they only differ by the amount of carbon incorporated. When carbon is incorporated, representative noise spectra of the input current spectral density, Si_B, show important generation-recombination (G-R) components, while no such components are observed in carbon free transistors. When the 1/f noise component is unambiguously observed, the associated figure of merit K_B has a very good value close to 4.10^-10 &mgr;m². In this paper we focus on the analysis of the G-R components associated with the presence of the carbon. Most of the observed Lorentzians are associated with Random Telegraph Signal (RTS) noise. No RTS noise is found in carbon free devices. The RTS noise appears to be due to electrically active defects formed by the addition of carbon, typically observed for concentrations above the bulk solid solubility limit in silicon. The RTS noise, amplitude &Dgr;IB and the mean pulse widths (t_H, t_L), are analyzed as a function of bias voltage and temperature. The RTS amplitude is found to scale with the base current and to decrease exponentially with temperature, independently of the carbon concentration. The mean pulse widths are found to decrease rapidly with bias voltage, as 1/exp(qV_BE/kT) or stronger. Our results confirm that electrically active C-related defects are localized in the base-emitter junction, and the RTS amplitude is explained by a model based on voltage barrier height fluctuations across the base-emitter junction induced by trapped carriers in the space charge region. The observed bias dependence of mean pulse widths seems to indicate that two capture processes are involved, electron and hole capture. These C-related defects behave like recombination centers with deep energy levels rather than electron or hole traps involving trapping-detrapping process.

We report, for the first time, the low frequency noise characteristics of both fully- and partially-depleted SiGe HBTs-on- SOI, both in forward and inverse modes of operation. These SiGe HBTs on thin-film SOI are then compared with bulk SiGe HBTs in order to evaluate how the fundamentally different device structure affects 1/f noise performance. In addition, the impact of substrate voltage, collector doping, and temperature on low-frequency noise is investigated.

We report on the low-frequency current and light noise in 515 nm green GaInN/GaN quantum well LEDs. The current noise was the superposition of the 1/f and the generation-recombination (GR) noise. The characteristic time of the GR process was found to be proportional to the reciprocal current for the entire current range. This dependence is the characteristic for the monomolecular non-radiative recombination. The dominance of the nonradiative recombination is in agreement with the measured low external quantum efficiency (EQE) <10%. Hence, the noise measurements point out that a low EQE is caused by the low internal quantum efficiency and not by an inefficient light extraction. The noise spectra of light intensity fluctuations were close to the 1/f noise and correlated with the LED quantum efficiency and with the recombination current. Higher noise corresponded to a smaller quantum efficiency and to a higher non-radiative recombination current. The relative spectral noise densities of the light intensity fluctuations within the LED spectral line increase with the wavelength decrease. Fluctuations at different wavelengths are found to be correlated.

The impact of carrier trapping at the substrate/buried oxide interface on the LF noise characteristics of Fully Depleted MOSFETs has been calculated. The channel LF noise analysis based on carrier number fluctuation approach has been extended to include charge variations at the substrate/buried oxide interface. The impact of fluctuations of substrate/BOX interfacial charge on the channel drain current has thereby been studied as a function of gate bias. The results suggest that substrate doping concentration, buried oxide thickness and dielectric material have non-negligible effect on the contribution of the substrate interface noise to the total device noise. To our knowledge, the contribution of this noise to the total noise of a FD-SOI device has never been studied.

In this paper we demonstrate that by exploiting the non linear characteristic of low noise PN junction diodes, a very low noise, high stability voltage reference can be obtained starting from a conventional solid state series voltage reference. In order to obtain such a result, a series connection of N identical diodes is supplied in the forward region of the I-V characteristic by means of a proper resistance. While the DC voltage drop across the diodes can be a large fraction of the voltage supplied by the reference, the noise introduced by the reference itself is reduced by a much larger factor because of the low value of the small signal equivalent resistance of the diodes. In its simplest implementation, such a voltage source would suffer from a relatively high temperature dependence of the supplied voltages because of the intrinsic properties of PN junctions. However, by resorting to a proper temperature control circuit, high stability can be obtained. As an example, by employing an AD586 voltage reference and with N=4, a 2.560 V reference has been obtained with a stability over temperature better than 50 μV/°C and a voltage noise as low as 2×10^-15, 6×10^-17 and 1.5×10^-17 V²/Hz at 100 mHz, 1 Hz and for frequencies larger than 10 Hz, respectively.

A detailed study of photosensitivity and noise characteristics of ultrafast InGaAsP/InP avalanche photodiodes with separate absorption, grading, charge and multiplication regions was carried out. Carrier multiplication and noise factors were evaluated. Noise origin in investigated APDs is 1/f, generation-recombination and shot noises. Different quality samples have been investigated and it is shown that noise characteristics well reflect APD quality problems. It is shown that low-frequency noise and excess shot noise characteristics are very sensitive to the APD quality problems and clear up physical processes in device structure. Noise characteristic analyses can be used for the APD quality problems revealing and optimal design development.

The Boltzmann equation with electron-electron (e-e) interactions has been reduced to a Fokker-Planck equation (e-e FP) in a previous paper. In steady-state conditions, its solution q₀(v) (where v is the electron speed) depends on the square of the acceleration a = eE/m. If we introduce the nonrenormalized zero-point field (ZPF) of QED, i.e., the one considered in stochastic electrodynamics, so that ⟨a²⟩ = ⟨(a_D.C. + a_ZPF)²⟩ ≃ a²_ZPF, then q₀(v) becomes similar to the Fermi-Dirac equation, and the two collision frequencies ν₁(v) and ν₂(v) appearing in the e-e FP become both proportional to 1/v in a small &dgr;v interval. The condition υ₁(v) ∝ υ₂(v) ∝ 1/v is at the threshold of the runaways. In the same &dgr;v range, the time-dependent solution q₀(v, &tgr;) of the e - e FP decays no longer exponentially but according to a power law ∝ &tgr;^-&egr; where 0.004 < &egr; < 0.006, until &tgr; → ∞. That extremely long memory of a fluctuation implies the same dependence τ^-&egr; for the conductance correlation function, hence a corresponding power-spectral noise S(f)∝ f^&egr;-1 where f is the frequency. That behaviour is maintained even for a small sample because the back diffusion velocity of the electrons in the effective range &dgr;v, where they are in runaway conditions, is much larger than the drift velocity.

We investigated the validity of the fluctuation dissipation theorem in the structural glass former triphenylolmethane triglycidyl ether. Polarization relaxation measurements were compared to the thermal fluctuation of the polarization. We observed that above the glass transition temperature, the fluctuation dissipation theorem is fully verified, whereas below the glass transition temperature the power noise spectrum measured subsequently to a temperature quench is more intense than that expected from response measurements. The amplitude of the fluctuation is distributed according to a non Gaussian distribution, whose origin is not strictly related to the presence of intense noise pulses.

The paper deals with low-frequency noise in RuO₂-glass thick resistive films at low temperatures. Careful measurements performed with ac technique reveal that below liquid helium temperature and in the low frequency limit excess noise of the films is a pure resistance noise for low bias voltage, but at larger voltages depends sublinearly on voltage square. The model is proposed which shows that the observed noise suppression is due to inhomogeneous heating of devices under test. In this model conduction is via hopping and the noise is due to fluctuation of activation energies of the inter-site conductances. Numerical simulations show that there is an interesting scaling of noise that can be used to identify the local (microscopic) mechanism of heat transfer from electron to phonon systems.

Semiclassical trajectory-based methods can now explain mesoscopic effects (shot-noise, conductance fluctuations, etc) in clean chaotic systems, such as chaotic quantum dots. In the deep classical limit (wavelength much less than system size) the Ehrenfest time (the time for a wavepacket to spread to a classical size) plays a crucial role, and random matrix theory (RMT) ceases to be applicable to the transport properties of open chaotic systems. Here we summarize some of our recent results for shot-noise (intrinsically quantum noise in the current through the system) in this deep classical limit. For systems with perfect coupling to the leads, we use a phase-space basis on the leads to show that the transmission eigenvalues are all 0 or 1-so transmission is noiseless [Whitney-Jacquod, Phys. Rev. Lett. 94, 116801 (2005), Jacquod-Whitney, Phys. Rev. B 73, 195115 (2006)]. For systems with tunnel-barriers on the leads we use trajectory-based semiclassics to extract universal (but non-RMT) shot-noise results for the classical regime [Whitney, cond-mat/0612122].

The complex ac conductance G(ω₀) of a system measures the dynamical response of the current to a small voltage excitation at frequency ω₀. It cannot in general be deduced from the only knowledge of the dc I(V ) characteristics. Similarly, we investigate the dynamical response of current noise to an ac excitation, i.e. the in-phase and out-of-phase response of current noise density S(ω) measured at frequency ω. We present a detailed calculation of this new response function χ_ω0 (ω), that we name noise susceptibility, at arbitrary frequencies for a coherent conductor in the scattering matrix formalism. We exemplify the relevance of our calculation by the measurement of the noise susceptibility of a tunnel junction in the quantum regime &barh;ω ~ &barh;ω₀> >k_BT, which is in remarkable agreement with our theory.

Gaussian generation-recombination is accepted to be a dominant mechanism of current noise source in quantum well systems biased by electric field normal to the layers. Recent experiments in n-type and p-type multiple quantum wells have revealed an additional pronouncedly non-Gaussian excess current noise with a low cut-off frequency in the kHz range. The non-Gaussian noise has been attributed to metastable spatial configurations of electric field. The metastability is originating from negative differential conductance caused by intervalley scattering in n-type wells and heavy and light holes tunneling in p-type wells. At a constant bias the system randomly switches between high resistivity state with low current flow and low resistive state with high current. The non-Gaussianity of the noise is more pronounced in p-type wells where the time traces of current fluctuations resemble closely two-level random telegraph signal. In n-type wells the telegraph-like fluctuations have not been straightforwardly observed. The non-Gaussianity of the noise in n-type systems has been revealed by nonzero skewness. The differences between noise properties of between n- and p-type systems have been attributed to small capture probability of electrons in n-type wells, as opposed to very high capture probability of holes in p-type wells. As a consequence the noise of any p-type multi-well system is dominated by the tunneling from the wells while in the n-type the noise appears as a superposition of many fluctuators associated with individual wells.

We present a short survey on fluctuation-enhanced gas sensing. We compare some of its main characteristics with those of classical sensing. We address the problem of linear response, information channel capacity, missed alarms and false alarms.

In this paper, we derive the input referred noise in terms of the on-pixel transistor device dimensions of the main noise sources of our array, namely, the flicker noise of the pixel thin-film transistors (TFTs), and the reset noise. Theoretical calculations and simulation results show that it is desirable to minimize the amplifier TFT gate dimensions, L₁ and W₁, and to maximize the read-out TFT gate width, W₂. Noise curves are presented as a function of transistor dimensions, allowing the designer to choose appropriate device dimensions when designing flat-panel imaging circuits. In addition, it is demonstrated how the optimal amplifier TFT gate width, W₁, for the lowest-noise design, changes as a function of the extraneous sense node capacitance. The noise simulations indicate that with proper device dimension design, it is possible to achieve sub-500 electron input referred noise performance.

We present a laser delay control system based on adaptive averaging which utilises the jitter noise of the laser to stabilise the delay more precisely. The system contains delay lines to measure and control the laser delay and a microcontroller that runs our control algorithm. The algorithm regulates the laser delay on the basis of the average of detected delay values, wherein the steps with which the delay is varied and the averaging length are chosen adaptively, depending on the distance from the target delay. Our complementary numerical simulations show that the jitter of the laser may play a beneficial role here: the error of the delay has a distinct minimum at a non-zero noise level. In a way similar to the dithering principle applied in analogue-to-digital conversion, averaging the noise-modulated detection instances yields a precision in setting the delay that is well beyond the resolution provided by detection time windows, and is close to the theoretical limit determined by the step size of the delay line we applied.

Soil bulk density affects water storage, water and nutrient movement, and plant root activity in the soil profile. Its measurement is difficult in field conditions. Vibration-induced conductivity fluctuation was investigated to quantify soil bulk density with possible field applications in the future. The AC electrical conductivity of soil was measured using a pair of blade-like electrodes while exposing the soil to periodic vibration. The blades were positioned longitudinally and transversally to the direction of the induced vibration to enable the calculation of a normalized index. The normalized index was expected to provide data independent from the vibration strength and to reduce the effect of soil salinity and water content. The experiment was conducted on natural and salinized fine sand at two moisture conditions and four bulk densities. The blade-shaped electrodes improved electrode-soil contact compared to cylindrical electrodes, and thereby, reduced measurement noise. Simulations on a simplified resistor lattice indicate that the transversal effect increases as soil bulk density decreases. Measurement of dry sand showed a negative correlation between the normalized conductivity fluctuation and soil bulk density for both longitudinal and transversal settings. The decrease in the transversal signal was smaller than expected. The wet natural and salinized soils performed very similarly as hypothesized, but their normalized VICOF response was not significant to bulk density changes. This lack of sensitivity might be attributed to the heavy electrodes and/or the specific vibration method used. The effects of electrode material, vibration method and soil properties on the experiment need further study.

We investigate the possibility of building linear amplifiers capable of enhancing the Signal-to-Noise and Distortion Ratio (SNDR) of sinusoidal input signals using simple non-linear elements. Other works have proven that it is possible to enhance the Signal-to-Noise Ratio (SNR) by using limiters. In this work we study a soft limiter non-linear element with and without hysteresis. We show that the SNDR of sinusoidal signals can be enhanced by 0.94 dB using a wideband soft limiter and up to 9.68 dB using a wideband soft limiter with hysteresis. These results indicate that linear amplifiers could be constructed using non-linear circuits with hysteresis. This paper presents mathematical descriptions for the non-linear elements using statistical parameters. Using these models, the input-output SNDR enhancement is obtained by optimizing the non-linear transfer function parameters to maximize the output SNDR.

We demonstrate how it is possible to increase the sensitivity of current noise measurement systems by exploiting the properties of a differential transconductance amplifier coupled with a four channels measurement system. In particular, it is demonstrated that, in proper conditions and by a proper elaboration of the acquired signals, the noise contribution coming from the active and passive devices that make up the transresistance amplifier can be virtually eliminated. The method is validated by means of actual measurements in order to demonstrate the effectiveness of the approach we propose.

Numerical and experimental modeling of the characteristics (sensitivity, constant time, noise properties) of high-T_c transition edge superconducting bolometers, operating in the various modes with an electrothermal feedback, are carried out: the mode with constant bias current, i.e. passive positive electrothermal feedback, the mode with constant bias voltage, i.e. passive negative electrothermal feedback and the mode with active electronic negative electrothermal feedback . It is shown, that in the modes with negative electrothermal feedback it is possible essentially to reduce constant time of bolometers till 5-15 of times in at some prize of the noise equivalent power on high frequencies. The estimation of influence of various noise components on a performance of the bolometers, operating with positive or negative electrothermal feedbacks, is carried out at the variation of bolometer parameters.

A new integrated CMOS micromachined inductive microphone is studied and characterized for mechanical-thermal noise. This acoustic sensor has one suspended membrane attached to the substrate with 4 arms, the I-beam or L-beam shaped attachments. This membrane has 1.4x1.4mm² active area, 22&mgr;g mass and its natural frequency is found to be around 250 kHz, for the I-beam and 134 kHz, for the L-beam attachment. We give a brief explanation of the superiority of this new design over conventional acoustic sensors. Then, some experimental points are discussed and solutions are given. This sensor is analyzed for mechanical-thermal noise by applying a new developed analysis based on mass and natural frequency. Our system damping factor is found to be 5x10^-2 N.s.m^-1, which gives a fluctuating force spectral density of 2.88x10^-11 N.Hz^-1/2. This corresponds to an A-weighted sound level of about 39 dB(A) SPL. A SNR value of 55 dB is found for an incident pressure of 1 Pa on the suspended membrane. The relationship between the SNR and the mechanical and geometrical characteristics of the suspended membrane is also investigated. Finally, our sensor mechanical noise displacement is evaluated, around 10^-15 m.Hz^-1/2, and plotted for the two attachment types.

In this paper, we investigated the coherent noise in communication systems and use a method for reducing the noise mixed with the signal. We use a general model of N-signal and N-noise frequency mixing. The numerical results are shown in this paper. A proper choice of the parameters can reduce the noise at the output of the data recovery system.

This work deals with the usage of micro-plasmas signal noise for solar cells diagnostic. When high electric field is applied to PN junction with some technological imperfections it produces in tiny areas of enhanced impact ionization called micro-plasmas which could lead to deterioration in quality or destruction of PN junction. On this account it is possible to use methods which indicate presence of micro-plasma in junction and enable quality and quantitative description of tested cells.

Voltage Amplifiers have been used to characterize the low-frequency noise of Heterojunction Bipolar Transistors (HBTs). They generally feature not only a lower noise floor, but also have less impact on simultaneous (two-port) measurements than Transimpedance Amplifiers, when moderate to high DC current regimes are considered. However, when the Device Under Test (DUT) is characterized under these regimes, common concepts such as unilateralism and frequency-independent small-signal parameters are no longer valid due to the frequency-dependent thermal response of the DUT (self-heating). It will be shown that depending on the conditions under which the measurements are carried out, the experimental data may vary for some orders of magnitude, leading to an incorrect characterization if the effect is disregarded.

Spatial and temporal fluctuations of the electric polarization were imaged in polymer thin films near the glass transition using electric force microscopy. Below the glass transition the fluctuations are quasi-static and spatial fluctuations were found to quantitatively agree with predictions for thermal fluctuations. Temporal fluctuations appear near the glass transition. Images of the space-time nanoscale dynamics near the glass transition are produced and analyzed. Local, complex dielectric susceptibility was also studied, and shows that dynamics on the free-surface are faster relative to the bulk.

We numerically examine noise fluctuations and hysteresis phenomena in charged systems that form stripe, labyrinth or clump patterns. It is believed that charge inhomogeneities of this type arise in two-dimensional (2D) quantum hall systems and in electron crystal structures in high temperature superconductors, while related patterns appear in manganites and type-I superconductors. Recent noise and transport experiments in two-dimensional electron gases and high temperature superconducting samples revealed both 1/f^α noise signatures and hysteretic phenomena. Using numerical simulations we show that 1/f^α noise fluctuations and hysteresis are generic features that occur in charge systems which undergo a type of phase separation that results in stripes, clumps, checkerboards, or other inhomogeneous patterns. We find that these systems exhibit 1/f^α fluctuations with 1.2 < α < 1.8, rather than simple 1/f or 1/f^α fluctuations. We also propose that the 2D metal insulator transition may be associated with a clump electron glass phase rather than a Wigner glass phase.

Pronounced random telegraph signals have been observed in voltages measured across current-biased thin-film YBa₂Cu₃O_7-δ superconducting bridges containing laser-processed channels for easy vortex motion. The appearance of two-level and three-level telegraph noise in bridges with single and double laser-written channels, respectively, is interpreted as experimental evidence for intermittent channeled vortex flow in current induced dissipative state in type-II superconductors.

In itinerant magnetic systems with disorder, the quantum Griffiths phase at T = 0 is unstable to formation of a cluster glass (CG) of frozen droplet degrees of freedom. In the absence of the fluctuations associated with these degrees of freedom, the transition from the paramagnetic Fermi liquid (PMFL) to the ordered phase proceeds via a conventional second-order quantum phase transition. However, when the Griffiths anomalies due to the broad distribution of local energy scales are included, the transition is driven first-order via a novel mechanism for a fluctuation induced first-order transition. At higher temperatures, thermal effects restore the transition to second-order. Implications of the enhanced non-Ohmic dissipation in the CG phase are briefly discussed.

A deterministic solver for the Langevin Boltzmann equation is presented, which is based on a spherical harmonics expansion, box integration, and a maximum entropy dissipation principle. The numerical properties of this method are very similar to the classical approaches (drift-diffusion or hydrodynamic models), and the same numerical methods can be used (ac analysis, adjoint method, harmonic balance, etc). Since the equations can be solved directly in the frequency domain, the full frequency range down to zero frequency is accessible. In addition, rare events can be simulated without excessive CPU times. This is demonstrated for a silicon NPN BJT. Not only the terminal current noise is calculated, but also the spatial origin of noise and the corresponding Green's functions.

Terminal current noise calculations are performed for a SiGe heterojunction bipolar transistor in a wide range of collector-emitter bias conditions. The generalized hydrodynamic (HD) model with a local temperature approach for avalanche generation is used. The parameters of the local temperature model are calibrated by matching the avalanche multiplication factor to results obtained by full-band Monte Carlo simulations. The noise figure calculation results are compared with experimental values and overall good agreement is obtained. The hydrodynamic and a drift-diffusion (DD) model are used to investigate terminal current noise due to impact-ionization. The behavior of the current noise spectral intensity is found to be different for the two models. The Fano factor of the collector current fluctuations is well described by the avalanche multiplication factor in the case of the DD model, whereas the HD model evidences no correlation between the Fano factor and the avalanche multiplication factor. The collector terminal electron transfer functions are used to discuss the difference.

Optical and electrical noises and correlation factor between optical and electrical fluctuations of nitride-based light emitting diodes (LEDs) have been investigated under forward bias. Their electrical, optical and noise characteristics were compared with ones of LEDs of other materials. LED noise characteristic changes during aging have been measured, too. It is found that optical and electrical noise spectra under forward bias for more reliable LEDs distinguish by lower 1/f type fluctuations and Lorentzian type noise at higher frequencies. LEDs with intensive 1/f noise demonstrate shorter lifetime. It is shown that reason of LED degradation is related with defects presence in device structure. These defects can be formed during device fabrication or appear during operation. An analysis of LED current-voltage and electrical noise characteristics under forward and reverse bias has shown that LEDs with intensive 1/f electrical noise, large reverse current (low reverse breakdown voltage) and larger terminal voltage under forward bias distinguish by short lifetime.

The fluctuation-dissipation analysis is carried out for the loop nonlinear RLC-circuit in equilibrium on the basis of the dual linear Langevin stochastic equations approach. It was found that the asymmetry of both the voltage thermal fluctuations at the capacitor and the current thermal fluctuations at inductor is a function of the resistor quadratic nonlinearity, the small signal capacity of capacitor, and the small signal inductance of inductor. At the same time the nonlinear characteristics of both capacitor and inductor do not influence the mentioned above asymmetries.

The current and frequency dependencies of the low frequency noise have been investigated in 4H-SiC p⁺-n junctions in the frequency range 10⁰-10⁴ Hz and at current densities from 10^-4 to 10¹ A/cm². Good quality of the p⁺-n diode under investigation has been ascertained by high value of the recombination time in the space charge region, &tgr;R ≈ 70 ns, extracted from current voltage characteristic. At small current densities j ⩽ 10^-3 A/cm², the spectral noise density S_I ∝1/f^3/2. At 10^-3 A/cm² < j < 10^-2 A/cm², the generation-recombination (GR) noise predominates. The amplitude of this GR noise non-monotonically depends on current. At j ⩾ 10^-2 A/cm², the 1/f (flicker noise) is dominant. A new model of GR noise of the recombination current in forward biased p-n junction has been proposed. The model assumes that a trap level located relatively close to the conduction band is responsible for the observed GR noise. The main contribution to the GR noise comes from the fluctuations of the charge state of the trap. The model describes well both current and frequency dependencies of the observed GR noise.

The main mechanisms of the conduction electrons mobility fluctuations, originating in n-type semiconductors with electron traps are investigated. It is shown that the current carriers mobility fluctuations are determined by the energy fluctuations. Fundamental sources of electron mobility fluctuations are established. The first source is established to be related with a non-elasticity of electron random scattering processes: intraband scatterings and electronic transitions "trap-conduction band". The second source of mobility fluctuations is established to be related with random character of the transitions of conductance electrons trough the potential barriers of p-n junctions or/and ohmic contacts.

Investigations of the static characteristics, responsivity, internal noises, and detectivity of the forward biased p-i-n photodetectors made on wide bandgap compensated semiconductors operating in double injection regime are presented. Noise related calculations are performed by utilizing "Impedance Field Method". Numerical simulations are made assessing 4H-SiC and GaN biased p-i-n photodiodes noise related characteristics. It is shown that forward biased p-i-n photodiodes have low level of thermal and generation-recombination noises and high values of sensitivity and detectivity at the room temperature.

This paper is intended to present the results of our experimental study of three new types of silicon solar cells G1, G3 and G5. The study is based on an analysis of the device transport and noise characteristics. This analysis shows that better quality (lower voltage noise spectral density) is exhibited by the structure of the groups of G3 specimens, this junction (of a thickness of about 1 um) is etched away from the rear side.

An analytical model for 1/f gate noise is developed and applied to the simulation and the characterization of ultra-thin MOSFETs. The proposed model is based on oxide trapping mechanisms and uses the concept of equivalent flat band voltage fluctuations. The developed model reproduces experimental behaviors. The power spectral density of flat band voltage fluctuation extracted from gate current low frequency noise is compared to one extracted from drain low frequency noise. Moreover, we have performed 1/f gate current noise for various drain voltage, and we show that there is no impact of the drain current noise on the gate current noise. We also investigate RTS noise observed on the gate leakage current. Finally, we present the characterization of the gate to drain overlap leakage current and its influence on gate current noise level.

This paper presents the challenges in the high-frequency noise characterization and modeling of sub-100nm MOSFETs for radio-frequency (RF) integrated circuits (IC). In general, it addresses three major issues - accuracy of high-frequency (HF) noise measurements, impact of test structure designs and physics-based noise models for the noise sources of interest - channel noise, induced gate noise and gate tunneling noise. In the first section, different HF measurement techniques, namely Y-factor method and power-equation method are reviewed. The impact due to the difference in the output impedances of a noise source in the hot and the cold states on the measurement accuracy is demonstrated. In the second section, different test structures and de-embedding procedures for noise and scattering parameter de-embedding to get rid of the parasitic effects from the probe pads and interconnections in a device-under-test (DUT) are reviewed. Special considerations on the measurement accuracy are paid to the shift of DC bias conditions. Finally, with the power spectral densities for the noise sources of interest obtained from the intrinsic noise parameters, different physics-based noise models for these noise sources in sub-100nm MOSFETs are discussed. The impact of the channel-length modulation (CLM) effect, the hot electron effect and the velocity saturation effect on the channel thermal noise and the impact of the gate tunneling noise on the noise performance of deep submicron MOSFETs are reviewed.

A new method based on the lumped-element network representation of the pad-set parasitics is developed to extract the intrinsic drain current noise source and gate resistance from raw measurement data instead of direct de-embedding. The length dependence of BSIM noise model is also corrected using a sub-circuit in the model file. With the new method, we can finally integrate an improved and hardware verified noise model into design kits.

Based on Boltzmann transport equation, the drift-diffusion, hydrodynamic, and Monte-Carlo physical models are accurately developed. The model equations are self-consistently solved with Poisson equation, and with Schrödinger equation when quantization effects take place, in one and two-dimensions to characterize the operation and optimize the structure of mm-wave devices. The effects of the devices dimensions, biasing conditions and operating frequencies on the accuracy of the obtained model (simulator) results are thoroughly investigated. Based on physical understanding of the models, the simulation results are analyzed and conclusions are drawn to fully determine the limits at which a certain device simulator can be accurately and efficiently used to characterize the noise behaviour of mm-wave devices.

The Correlation Spectrum Analyzer, thanks to the presence of two independent acquisition channels, has demonstrated to reach very high performance in measuring noise spectra and to be extremely flexible in adapting to different devices under test (DUT) in term of impedance values, of flowing standing current, of DC applied voltage and of the physical quantity to be measured, either current or voltage. In addition, it can selectively extract the noise contribution of a specific current flow in multi-electrodes devices. The paper will briefly highlights these features together with the influence of the DUT characteristics, such as its impedance to ground and the cross-impedance between the two electrodes connected to the instrument input ports, in determining the ultimate limits in the performance of the instrument in terms of its sensitivity, its precision and its spectral extension. A practical realisation for measurements made with an AFM especially modified for correlation investigations is also commented.

In this contribution, we review the use of physical models for the noise simulation of devices operated in nonlinear conditions, thus requiring a full mixed-mode simulation of the device and of the embedding circuit. After presenting a detailed formulation of the model, we discuss two significant case studies: a downconversion GaAs MESFET mixer, and a detailed analysis and physical interprettion of low-frequency noise upconversion in a pn junction.

During the last decades, several theoretical models describing phase noise of oscillator signals have been established. Verification of these models has mainly been done by computer simulations. However, what is still missing is a rigorous experimental validation of diverse aspects of these models. This is not an easy job, since internal noise sources of the measurement equipment superimpose the effects to be measured. Therefore, a novel measurement method is introduced. Relatively strong, additional noise-sources are deliberately included into oscillator circuits. Controlling the power and the spectrum of these sources allows to clearly identifying the effects of these sources to the spectrum of the oscillator's output signal. This paper shows typical measurement results and their interpretations. It turns out that at least for the oscillator under test, modeling with simple additive noise might not be sufficient. Rather, multiplicative noise must also be taken into account. The consequence is that the output of oscillators might not only be affected by phase noise but also by amplitude noise. Under these circumstances, models that explicitly exclude amplitude noise in oscillators might need completion.

Switching activity of logic gates in a digital system is a deterministic process, depending on both circuit parameters and input signals. However, the huge number of logic blocks in a digital system makes digital switching a cognitively stochastic process. Switching activity is the source of the so-called "digital noise", which can be analyzed using a stochastic approach. For an asynchronous digital network, we can model digital switching currents as a shot noise process, deriving both its amplitude distribution and its power spectral density. From spectral distribution of digital currents, we can also calculate the spectral distribution and the power of disturbances injected into the on-chip power supply lines.

Analytical expressions for the PM noise in FET oscillators are derived in terms of the FET equivalent circuit elements and the passive circuitry. Efficient methods to reduce the PM noise in fundamental and in harmonic mode are suggested and implements. The effects of the different FET equivalent circuit parameters on large-signal, small-signal, and noise behaviour of FET oscillators are thoroughly investigated. Finally, the effects of harmonic signal on both fundamental and harmonic output noise are determined.

We study the energy and magnetization noise spectra associated with first and second order phase transitions by using Monte Carlo simulations of the Ising model and 5-state Potts model in 2D. For a finite size system, the total noise power and the low frequency white noise S(f < f_knee) increase as T_c is approached. In the thermodynamic limit S(f < f_knee) diverges but f_knee → 0 and the total noise power vanishes. f^-1_knee is approximately the equilibration time. At high frequencies S(f > f_knee) ~ f^-μ. For the Ising model, we relate μ to the critical exponents.

Studies of low-frequency noise in the c-axis resistance of lightly doped La_2-x Sr_xCuO₄ (x = 0.03) have revealed distinct switching fluctuations at low temperatures and in magnetic fields B of up to 9 T parallel to the c-axis of the crystal. The switching noise is modulated by some slower events and becomes less prominent with increasing temperature T. Our results demonstrate the existence of multiple metastable states in the presence of B. The overall behavior of the noise is consistent with the picture of microscopic segregation of doped holes into hole-rich regions separated by undoped domains in CuO₂ planes. It also strongly suggests that interactions should be included in possible theoretical models to describe the data.

The electric conduction and low-frequency noise were investigated in silicon nitride-based ceramics doped with different carbon allotropes as multi-wall carbon nanotubes, black carbon and graphite powder. The electric conduction was found unstable in time. This instability does not depend on the atmosphere and on the possible variation of the temperature. The noise spectra show 1/f character, however the magnitude of the noise differ for the different dopants, and strongly depends on the pressure of sintering. The comparison of the resistance values and the noise magnitudes suggest that the carbon dopants form percolation networks. The carbon is distributed most likely at the surface of the ceramic particles like the Swiss-Cheese model.

Noise was studied in an MgB2 thin film grown on a SiN substrate, with a superconducting transition temperature, Tc, near 39K. At the mid-point of the transition and at 10Hz a noise spectral density S_v = 0.34nVHz^1/2 was measured. The temperature noise, Kn , of the MgB2 film at different frequencies is compared to that of cuprate high temperature superconducting (HTS) thin films (with Tc ~ 90 K) used currently in transition-edge devices. Kn values predict that 2-D arrays of high performance infrared devices can be developed using MgB2.