Hooge Model Research Articles

Excess noise and thermoelectric effect in magnetron-sputtered VO2 thin films

This work presents the excess noise and thermoelectric (Seebeck) measurements on polycrystalline vanadium dioxide (VO2) thin films. Noise spectral power density (SPD) of current fluctuations in the semiconducting (SC) phase had a typical flicker noise (f−γ) characteristic with an average slope parameter γ of 1.13. Normalized SPD (Sn) values obtained in the SC-phase indicate that the noise originates in the bulk of the film. On the contrary, in the metallic (M)-phase, γ values were greater than unity, and the observed Sn values indicated that the origin of the noise is most likely from the contacts or surface rather than the bulk. A general decrease was observed in Sn by a factor of 4–5 from the SC- to M-phase. Moreover, Sn in the SC-phase showed no temperature dependence. An interpretation based on the number of charge carrier fluctuations in Hooge's model led to an unrealistically high Hooge parameter and had to be ruled out. We propose that the fluctuations are related to the mobility fluctuations of carriers arising primarily from grain-boundary scattering which explains the observed characteristics well. The Seebeck coefficients (S) obtained under both heating and cooling schedules showed the n-type nature of magnetron-sputtered VO2 films in the SC-phase. Differently, in the M-phase, the S value was positive. The S values obtained from the cooling schedule signified the low percolation threshold of the metal-to-insulator transition already demonstrated for VO2 thin films grown on r-cut sapphire using the Efros–Shklovskii percolation model.

Compact model for the bias-depended low-frequency noise in organic thin-film transistors due to carrier-number and mobility-fluctuation effects

A charge-based compact model for the bias-dependent low-frequency noise in organic thin-film transistors is presented. The model combines the carrier-number fluctuation effect and the fluctuation of the carrier mobility according to the Hooge model to predict the drain-current noise. The model has been verified using experimental data from a large number of organic transistors with two different channel lengths fabricated in the inverted staggered device architecture on a flexible polymeric substrate.

Review on 1/<i>f</i> noise and its research progress in two-dimensional material graphene

Noise is a signal. Low-frequency noise with a 1/<i>f</i>-type spectral density (1/<i>f</i> noise) has been observed in a wide variety of systems. There are plenty of physical processes under the 1/<i>f</i> noise phenomenon. It is not only a useful tool for scientific research, but also a quantitative probe for the performance of electronic devices. In this paper, the 1/<i>f</i> noise models are summarized from the general mathematical forms to physical processes. Based on Markov process and diffusion process, two general mathematical models of 1/<i>f</i> noise are introduced respectively. On this basis, tracing the development history, several typical physical models are described, including Mc Whorter model, Hooge model, Voss-Clarker model, Dutta-horn model, interference model and unified Hung model. The advent of the two-dimensional material graphene offers unique opportunities for studying the mechanism of 1/<i>f</i> noise. In the fact of the cloudy and even contradictory conclusions from different reports, this paper combs the consensus accepted widely. An analysis model based on three-level classification for the graphene low-frequency noise study is built, which divides the noise into intrinsic background 1/<i>f</i> noise, 1/<i>f</i>-like noise and Lorentz-like noise. Typical research on the related mechanism at each level is analyzed, and the dominant mechanisms are summarized. Further, we focus on the gate-modulated characteristic spectrum shape of 1/<i>f</i> noise from different reported experiments, which may be a key to the material internal scattering mechanism and charge distribution. The experimental measurements show that the characteristic shape is variable, and mainly exists in three forms: V-type, Λ-type and M-type. Through the comparative analysis of graphene cleanliness, bias current (voltage) and other experimental parameters, the possible causes of the complexity and variability of the characteristic shape are analyzed, showing that the main reason may be that the experimental parameters are not strictly controlled, and the selection of measuring point is unreasonable. In order to capture the accurate noise characteristics and reveal the noise mechanism clearly, a standard 1/<i>f</i> noise measurement paradigm is proposed in this work to guide the effective research on graphene 1/<i>f</i> noise and the distinction betweenintrinsic noise and extrinsic noise. The standard paradigm includes three processes. The first process is to prepare suspended graphene samples, the second one is to remove the surface contamination by using the methods such as current annealing, and the third one is to test the curve of the 1/<i>f</i> noise amplitude versus the bias voltage or current. Based on this curve, suitable test points can be selected for different measurement schemes. The proposed standard intrinsic background 1/<i>f</i> noise measurement paradigm may be expected to clarify and reveal the characteristics of graphene 1/<i>f</i> noise.

Fast-Response Superconducting Titanium Bolometric Detectors

High time resolution optical/infrared (IR) astronomy will require fast response detectors. In order to meet such requirement, cryogenic optical/IR detectors, such as superconducting tunnel junctions and transition-edge sensors, are under development. Of these cryogenic detectors, superconducting titanium (Ti) bolometric detectors, with a transition temperature of around 300 mK, based on the electron-phonon decoupling mechanism, are promising in fast response. In this paper, we report on the characterization of electro-thermal properties of a small-size (1 μm × 1 μm × 37 nm) superconducting Ti detector. The low-frequency noise of Ti film was fitted by empirical Hooge model. A discrepancy between the Hooge constant of the Ti film and that of normal metals shows disorder in the Ti film. Thermal conductance was extracted via measured current-voltage curves at different bath temperatures. The time constant was calculated as tens of nanoseconds, which was faster than expected. The fast response potentially enables the high-speed optical/IR astronomical observations. Detailed experimental and analytical results are also presented.

Low frequency noise in hydrogenated p-type amorphous silicon thin films

We report on electrical noise measurements of p-type a-Si:H thin films prepared by plasma enhanced chemical vapor deposition. Samples were grown at various boron concentrations and hydrogen dilution of the silane precursor. Measurements were made at temperatures ranging from 210K to 450K. In this temperature range, Mott variable range hopping conduction describes the electrical conductivity, and the noise has a 1/fγ component. The exponent γ for temperatures below 400K is approximately 1, and the noise follows the Hooge model. For temperatures between 240K and 380K, the 1/f noise was found to be independent of the conductivity. Therefore, the carrier concentration does not change appreciably with temperature and the change in conductivity is due to the temperature dependence of the hole mobility. The normalized Hooge parameter correlates with the Mott hopping parameter, T0M, and in turn, to the material dopant boron concentration and hydrogen dilution levels. For temperatures above 400K, the frequency exponent, γ, is larger than 1, indicative of a generation-recombination trap contribution to the noise. From the dependence of the normalized Hooge parameter to the Mott characteristic temperature T0M, we conclude that the electrical 1/f noise in p-type a-Si:H is associated with hopping conduction.

Low-Frequency Noise in Gate Tunable Topological Insulator Nanowire Field Emission Transistor near the Dirac Point**Supported by the National Basic Research Program of China under Grant No 2012CB921703, the National Natural Science Foundation of China under Grant Nos 11174357 and 11574379, and the Strategic Priority Research Program of Chinese Academy of Sciences under Grant No XDB07010300.

Low-frequency flicker noise is usually associated with material defects or imperfection of fabrication procedure. Up to now, there is only very limited knowledge about flicker noise of the topological insulator, whose topologically protected conducting surface is theoretically immune to back scattering. To suppress the bulk conductivity we synthesize antimony doped Bi2Se3 nanowires and conduct transport measurements at cryogenic temperatures. The low-frequency current noise measurement shows that the noise amplitude at the high-drain current regime can be described by Hooge's empirical relationship, while the noise level is significantly lower than that predicted by Hooge's model near the Dirac point. Furthermore, different frequency responses of noise power spectrum density for specific drain currents at the low drain current regime indicate the complex origin of noise sources of topological insulator.

1/f Noise in Mott Variable Range Hopping Conduction in p-type Amorphous Silicon

ABSTRACTWe report on electrical conductivity and noise measurements made on p-type hydrogenated amorphous silicon (a-Si:H) thin films prepared by Plasma Enhanced Chemical Vapor Deposition (PECVD). The temperature dependent electrical conductivity can be described by the Mott Variable Range Hopping mechanism. The noise at temperatures lower than ∼ 400K is dominated by a 1/f component which follows the Hooge model and correlates with the Mott conductivity. At high temperatures there is an appreciable G-R noise component.

Low-frequency (1/f) noise in nanocrystal field-effect transistors.

We investigate the origins and magnitude of low-frequency noise in high-mobility nanocrystal field-effect transistors and show the noise is of 1/f-type. Sub-band gap states, in particular, those introduced by nanocrystal surfaces, have a significant influence on the 1/f noise. By engineering the device geometry and passivating nanocrystal surfaces, we show that in the linear and saturation regimes the 1/f noise obeys Hooge's model of mobility fluctuations, consistent with transport of a high density of accumulated carriers in extended electronic states of the NC thin films. In the subthreshold regime, the Fermi energy moves deeper into the mobility gap and sub-band gap trap states give rise to a transition to noise dominated by carrier number fluctuations as described in McWhorter's model. CdSe nanocrystal field-effect transistors have a Hooge parameter of 3 × 10(-2), comparable to other solution-deposited, thin-film devices, promising high-performance, low-cost, low-noise integrated circuitry.

Carrier-number fluctuations in the 2-dimensional electron gas at the LaAlO3/SrTiO3 interface

The voltage-spectral density SV (f) of the 2-dimensional electron gas formed at the interface of LaAlO3/SrTiO3 has been thoroughly investigated. The low-frequency component has a clear 1/f behavior with a quadratic bias current dependence, attributed to resistance fluctuations. However, its temperature dependence is inconsistent with the classical Hooge model, based on carrier-mobility fluctuations. The experimental results are, instead, explained in terms of carrier-number fluctuations, due to an excitation-trapping mechanism of the 2-dimensional electron gas.

Possible unified model for the Hooge parameter in inversion-layer-channel metal-oxide-semiconductor field-effect transistors

This paper proposes a possible unified model for the Hooge parameter by considering the impact of transport dimensionality on the Hooge parameter behavior of various inversion-layer-channel metal-oxide-semiconductor field-effect transistors. Past experiments show that the Hooge parameter has a couple of peculiar behaviors. Based on a phenomenological consideration, the original mobility-based model for the Hooge parameter is shown to provide only a partial understanding of the results. It is also observed that, in contrast to past models, the interpretation of some aspects of the Hooge parameter strongly depends on how the two fluctuation modes, the carrier-density fluctuation and the mobility fluctuation, correlate. The phenomenological model proposed here gives a fundamental physical basis that allows important aspects of the Hooge parameter to be interpreted; the model also introduces three basic parameters (the Hooge parameter elements for the carrier-density fluctuation, the mobility fluctuation, and the cross-correlation component). Theoretical expressions for the three basic Hooge parameters are given by merging the fundamental Hooge model, Handel's theory, statistical physics, and quantum-mechanical transport physics. The gate voltage dependence of the Hooge parameter can be explained reasonably well by stating that the screening length rules the dielectric function and that the mobility fluctuation and carrier density fluctuation are correlated. Finally, the theoretical models are examined against the results of past experiments.

Electrical noise characteristics of a doped silicon microcantilever heater-thermometer

We measure the electrical noise characteristics of doped silicon microcantilevers during cantilever self-heating over the temperature range 296–781 K. The dominant noise source is 1/f below about 10 kHz, while at higher frequency, the dominant noise source is Johnson noise. The 1/f noise matches the Hooge model. The noise floor is about 10 nV/Hz1/2 and depends upon temperature, matching the theoretical Johnson noise. The Johnson noise-limited temperature resolution is about 1 μK/Hz1/2.

Noise and electric field characterization of irradiated SrTiO3

SrTiO3 (STO) is a band insulator with a perovskite crystallographic structure, widely used as substrate for the deposition of other perovskite materials, for instance manganites or cuprates. STO surface becomes conductive under Ar+ ion irradiation, exhibiting similar properties to STO/LaAlO3 interface or bulk reduced STO. We report the transport and noise properties as function of temperature and electric field of Ar+ irradiated STO exhibiting at its surface a high mobility electron gas. This system shows metallic properties with low charge densities allowing mobility measurements. The low frequency 1/f noise presents an unexpected linear dependence with the mobility which cannot be described by the usual Hooge model. The effect of the electric field at a given temperature on the mobility, magnetoresistance and low frequency noise is also presented.

Unusual low-frequency noise in irradiatedSrTiO3

We report the transport and noise properties as function of temperature and electric field of ${\text{Ar}}^{+}$ irradiated ${\text{SrTiO}}_{3}$ exhibiting at its surface a high-mobility electron gas. This system exhibits metallic properties with low-charge densities allowing mobility measurements. The low-frequency $1/f$ noise presents a linear dependence with the mobility. This nonintuitive variation requires a rewriting of the commonly used Hooge model.

Physics-Based Analysis and Simulation of $\hbox{1}/f$ Noise in MOSFETs Under Large-Signal Operation

This paper presents a study on 1/f noise in MOSFETs under large-signal (LS) operation, which is important in CMOS analog and RF integrated circuits. The flicker noise is modeled with noise sources as a perturbation in the semiconductor equations employing McWhorter's oxide-trapping model and Hooge's empirical 1/f noise model. Numerical results are shown for 1/f noise in the MOSFET in both small-signal operation and periodic LS operation. It is shown that McWhorter's model does not give any significant 1/f noise reduction when the oxide traps are distributed uniformly in energy and space. In contrast, Hooge's model gives almost 6-dB 1/f noise reduction as the gate off-voltage decreases below the threshold voltage. It is found that both models fall short of explaining the noise reduction by more than 6 dB, as observed experimentally in the literature. However, when only one active oxide trap is considered, which generates random telegraph signal (RTS) in drain current, the LS operation gives more than 6-dB low-frequency RTS noise reduction.

Noise Minimization of MOSFET Input Charge Amplifiers Based on $\Delta\mu$ and $\Delta{\rm N}$$1/f$ Models

The optimization of the noise performance of integrated complementary metal-oxide semiconductor (CMOS) charge amplifiers is studied in detail considering accurate 1/ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> noise modeling for the input metal-oxide semiconductor field-effect transistor (MOSFET) biased in a strong inversion-saturation region. This paper aims to generalize and correct previously published analyses which have been based on two limiting and sometimes not applicable assumptions: a fixed MOSFETs bias current and the general validity of the McWhorter 1/ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> noise model. This study considers the two main 1/ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> noise models: (1) the mobility fluctuation, known as Deltamu or Hooge model, which is followed by p-channel MOSFETs and (2) the carriers number fluctuation, also known as DeltaN or McWhorter model, which is applicable only for n-channel MOSFETs. The front-end noise optimization is made with the 1/ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> component alone, thus determining the ultimate performance, and also considering the presence of series and parallel white noise sources. It is shown that different design criteria are valid of p- or n-channel MOSFETs: the Deltamu model results in an optimum bias current and a different optimum gate width with respect to DeltaN model. Two-dimensions suboptimum noise minimization criteria are derived when power or area constraints are imposed to the circuit design. Starting from experimental data on CMOS 1/f noise, examples of application of the presented analysis are shown to predict the lower limits of the 1/ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> noise contribution for the currently available CMOS technologies.

Different mechanism to explain the 1∕f noise in n- and p-SOI-MOS transistors fabricated on (110) and (100) silicon-oriented wafers

The investigation of the low frequency noise in p- and n-channel semiconductor-on-insulator–metal oxide semiconductor transistors fabricated on (100) and (110) silicon-oriented wafers using high advanced processes has been carried out. While for both orientations the 1∕f noise in the n-channel transistors can be explained through the ΔN formalism, the p-channel ones seem to follow the Hooge model. In addition, the new orientation presents a noise level higher than the conventional one. Furthermore, the authors showed that when there is a gap of one decade between the Si(100) and Si(110) p-channel transistors, this one has been reduced to a factor of 2 in the case of the n-channel ones. Finally, by combining the highly advanced microwave-excited high-density plasma oxidation process with the alkali-free five-step cleaning process, it has been possible to fabricate on both surfaces a very high quality oxide with a very low density of traps.

Noise characteristics and modeling of silicon-on-insulator insulated-gate pn-junction devices

This article describes the noise characteristics of various silicon-on-insulator insulated-gate pn-junction devices with anode-offset regions. The static characteristics of these devices are modeled for the noise analysis; the model is composed of a series of a metal-oxide-semiconductor field-effect transistors and the pn junction. It is shown experimentally that the noise power of the devices is proportional to In (n&amp;gt;0), where I is the anode current. Since the noise characteristics are not explained by the conventional theory, a phenomenological model is proposed. It is shown that the proposed basic model, which is compatible with the conventional Hooge model, can explain the experimental results. The influence of anode-offset length is also discussed and modeled.

Comparison of excess 1/f noise spectra in trimmed and untrimmed thick film resistors

Low frequency excess 1/f noise in the frequency range 1-104 Hz and conductivity are measured and analysed in trimmed and untrimmed bismuth ruthenate thick film resistors (TFRs) with an aspect ratio of 0.04. The excess flicker noise exhibits a 1/f γ spectrum with γ ≈ 1 which scales with the square of the dc current. Although both the temperature coefficient of resistance and the conductivity of the TFRs did not change significantly upon trimming, we observed a substantial increase in the relative noise index C for trimmed TFRs. The Hooge parameter α H for untrimmed TFRs was estimated to be ∼ 1.1 × 10−3. Application of the Hooge model to trimmed TFRs indicated that trimming increases the values of α H. Further, if V is the volume of the TFR, the noise of the trimmed resistors did not exhibit the expected C ∝ 1/V behaviour that is observed for untrimmed TFRs. These observations may be due to a combination of reasons such as laser trimming induced inhomogeneous damage or a possible reduction in the Vandamme effective volume; trimmed TFRs exhibited an effective volume in the range 0.18-0.38.

1/f noise in InGaAs/GaAs linear graded buffer layers

Noise spectroscopy has been used as a sensitive technique to assess the quality of In/sub x/Ga/sub 1-x/As linear graded buffer layers grown onto GaAs substrates. Samples having different dislocation structure and quality, determined by design and growth conditions, have been analyzed. Samples with a high dislocation density have been shown to be very efficient 1/f noise sources, with Hooge's parameters (/spl alpha//sub H/) as high as 4/spl times/10/sup -1/. A Hooge model, based on mobility fluctuation in the depletion regions surrounding dislocations, has been used to explain the observed dependence of /spl alpha//sub H/ on mobility /spl mu/. While a power law /spl alpha//sub H//spl prop//spl mu//sup /spl beta// with /spl beta//spl ap/-1 is found for the noise generated in samples with a high dislocation density (HDD), /spl beta//spl ap/+2 seems to hold when sample quality improves, where much lower /spl alpha//sub H/ values (100 times) are obtained. These results allow to correlate the scattering centers that limit the mobility with the noise sources existing in the conducting layer of these structures.

1/f noise in n-channel silicon-gate MOS transistors

It is found that equivalent gate noise power for l/f noise in n-channel silicon-gate MOS transistors at near zero drain voltage at room temperature is empirically described by two noise terms, which vary as K_{1}(q/C_{ox}) (V_{G} -V_{T})/f and K_{2}(q/C_{ox})^{2}/f, where V_{G} is gate voltage, V T is threshold Voltage, and C ox is gate-oxide capacitance per unit area. Unification of carrier-density fluctuation (McWhorter's model)and mobility fluctuation (Hooge's model) can account for the experimental data. The comparison between the theory and experiment shows that the carrier fluctuation term K 2 is proportional to oxide-trap density at Fermi-level. The mobility fluctuation term K 1 is correlated to K 2 , being proportional to \radic K_{2} . The origin of this correlation is yet to be clarified.