Noise In Semiconductors Research Articles

1/f noise in semiconductors arising from the heterogeneous detrapping process of individual charge carriers

Abstract We propose a model of 1 / f noise in semiconductors based on the drift of individual charge carriers and their interaction with the trapping centers. We assume that the trapping centers are homogeneously distributed in the material. The trapping centers are assumed to be heterogeneous and have unique detrapping rates. We show that uniform detrapping rate distribution emerges as a natural consequence of the vacant trap depths following the Boltzmann distribution, and the detrapping process obeying Arrhenius law. When these laws apply, and if the trapping rate is low in comparison to the maximum detrapping rate, 1 / f noise in the form of Hooge’s relation is recovered. Hooge’s parameter, α H, is shown to be a ratio between the characteristic trapping rate and the maximum detrapping rate. The proposed model implies that 1 / f noise arises from the temporal charge carrier number fluctuations, not from the spatial mobility fluctuations.

Unveiled Influence of Sub‐gap Density of States on Low‐Frequency Noise in Si‐Doped ZnSnO TFTs: Does Correlated Mobility Fluctuation Model Suffice?

AbstractThe presence of low‐frequency noise (LFN) in amorphous oxide semiconductor (AOS) thin‐film transistors (TFTs) is of utmost concern, prompting extensive investigations into the analysis of LFN. However, prior research endeavors have tended to overlook the significance of the sub‐gap density of states (DOS) in the LFN analysis, resulting in an incomplete comprehension. To bridge this knowledge gap, the influence of sub‐gap DOS is demonstrated on LFN in Si‐doped ZnSnO (SZTO) thin‐film transistors (TFTs) under various conditions. The SZTO TFTs is intentionally subjected to positive bias stress and hot carrier stress in order to control the sub‐gap DOS and investigate how this change affects the LFN characteristics. It is revealed that the non‐uniform energetic distribution of sub‐gap DOS induces bias‐dependent excess noise in the SZTO TFTs. Additionally, self‐recovery behavior after the HCS is observed, accompanied by a commensurate reduction in 1/f noise. These empirical observations provide evidence that the conventional correlated mobility fluctuation model used to explain LFN in AOS TFTs is insufficient and underscores the critical importance of considering subgap DOS when analyzing LFN of AOS TFTs.

Editorial Preface

The 23rd Russian Youth Conference on Physics of Semiconductors and Nanostructures, Opto- and Nanoelectronics (RYCPS) was held in Saint Petersburg on November 23 – 26, 2021. It was organized by Peter the Great St. Petersburg Polytechnic University.The program of the Conference included semiconductor technology, heterostructures with quantum wells and quantum dots, bulk properties of semiconductors, opto- and nanoelectronic devices and new materials. Given the restrictions on meetings of a large number of people associated with COVID-19, the organizing committee of the conference decided to hold it in a virtual format. The oral sessions were held on the Zoom platform, and the poster session was organized using the Miro online whiteboard and the Skype platform. This provided an opportunity for valuable discussions between the conference participants and experienced scientists.The conference included two invited talks given by leading scientists from Ioffe Institute, devoted to actual problems and major advances in physics and technology. The keynote speakers were Anton Vershovskii (presentation "Optical quantum sensors based on thermal atoms and atom-like structures") and Mikhail Glazov (presentation "Spin noise in semiconductors"). Students, graduate and postgraduate students presented their results on plenary and poster sessions. The total number of accepted abstracts published in Russian (the official conference language) was 105. Here we publish 24 selected papers in English.Like previous years, the participants were involved in the competition for the best report. Certificates and cash prizes were awarded to a number of participants for the presentations selected by the Program Committee. Alexey Kuznetsov (Alferov University, Saint Petersburg) was awarded for the best presentation among students with a report "Influence of plasmonic effects on the localization of electromagnetic waves in GaP nanowires". Sergey Savchenko (Ural Federal University, Yekaterinburg) was awarded for the best presentation among postgraduate students with a report "Thermal quenching of luminescence of excitons and defect centers in InP/ZnS quantum dots". Works with potential applications were recommended for participation in the following competition for support from the Russian Foundation for Assistance to Small Innovative Enterprises in Science and Technology.List of Editors, Organizers, Sponsors, Program Committee, Organizing Committee are available in this pdf.

1/f noise under drift and thermal agitation in semiconductor materials

Voss and Clarke observed 1/f noise in the square of Johnson noise across samples in thermal equilibrium without applying a current. We refer to this phenomenon as “thermal 1/f noise”. Voss and Clarke suggested spatially correlated temperature fluctuations as an origin of thermal 1/f noise; they also showed that thermal 1/f noise closely matches the 1/f spectrum obtained by passing a current through the sample. An intermittent generation–recombination (g–r) process has recently been introduced to interpret 1/f noise in semiconductors. The square of this intermittent g–r process generates a 1/f noise component which correlates with Voss and Clarke’s empirical findings. Traps which intermittently rather than continuously generate g–r pulses are suggested as the origin of 1/f noise under drift and thermal agitation. We see no need to introduce correlated temperature fluctuations or oxide traps with a large distribution of time constants to explain 1/f noise.

A quantum bound on the 1/f noise in semiconductors with a conical energy-momentum dispersion

The quantum indeterminacy caused by non-commutativity of observables at different times sets a lower bound on the voltage noise power spectrum in any conducting material. This bound is calculated explicitly in the case of semiconductors with a conical energy-momentum dispersion of charge carriers. It possesses all characteristic properties of 1/f noise. Its momentum decomposition is found to be singular at zero particle momentum, a measurable consequence being a sharp peak in the noise magnitude at small charge carrier density. In application to monolayer graphene, this peak becomes M-shaped on account of a continuous transition from the electron to hole conductivity. A comparison with experimental data is made which demonstrates that the calculated power spectrum is close in magnitude and congruent to the observed.

Low‐Frequency Electronic Noise in Quasi‐2D van der Waals Antiferromagnetic Semiconductor FePS3—Signatures of Phase Transitions

AbstractLow‐frequency current fluctuations, i.e., noise, in the quasi‐2D van der Waals antiferromagnetic semiconductor FePS3 with the electronic bandgap of 1.5 eV is investigated. The electrical and noise characteristics of the p‐type, highly resistive, thin films of FePS3 are measured at different temperatures. The noise spectral density is of the 1/f‐type over most of the examined temperature range but reveals well‐defined Lorentzian bulges, and increases strongly near the Néel temperature TN = 118 K (f is the frequency). Intriguingly, the noise spectral density attains its minimum at temperature T ≈ 200 K, which is attributed to an interplay of two opposite trends in noise scaling—one for semiconductors and another for materials with the phase transitions. The Lorentzian corner frequencies reveal unusual dependence on temperature and bias voltage, suggesting that their origin is different from the generation—recombination noise in conventional semiconductors. The obtained results are important for proposed applications of antiferromagnetic semiconductors in spintronic devices. They also attest to the power of the noise spectroscopy for monitoring various phase transitions.

Influence of penetrating radiations on electrical low frequency noise of semiconductors

The influence of penetrating radiations on the electrical low-frequency noise of semiconductors is studied. Expression is calculated that determines the number of structural defects in semiconductors arising from exposure to penetrating radia-tion. General form expression is calculated for the spectrum of electrical low-frequency noise in semiconductors when exposed to penetrating radiation. Quanti-tative relationship was established between the spectrum of electrical low-frequency noise and the development of disturbances in the structure of semicon-ductors caused by penetrating radiations. The results obtained can be used to de-termine the spectra of electrical noise in semiconductors of various types and in numerous semiconductor devices. The results of the article have practical applica-tions. Calculated expressions allow to make estimates of the intensity of electrical low-frequency noise, from which conclusions can be drawn about possibility of functioning and reliability of semiconductor devices. Established relationship be-tween electrical noise and radiation defects can be used to estimate, based on spec-tral characteristics of the noise, the defectiveness of structure of semiconductors subjected to radiation damage.

Electronic noise of warm electrons in semiconductors from first principles

The ab-initio theory of low-field electronic transport properties such as carrier mobility in semiconductors is well-established. However, an equivalent treatment of electronic fluctuations about a non-equilibrium steady state, which are readily probed experimentally, remains less explored. Here, we report a first-principles theory of electronic noise for warm electrons in semiconductors. In contrast with typical numerical methods used for electronic noise, no adjustable parameters are required in the present formalism, with the electronic band structure and scattering rates calculated from first-principles. We demonstrate the utility of our approach by applying it to GaAs and show that spectral features in AC transport properties and noise originate from the disparate time scales of momentum and energy relaxation, despite the dominance of optical phonon scattering. Our formalism enables a parameter-free approach to probe the microscopic transport processes that give rise to electronic noise in semiconductors.

Adaptive Algorithms for Measuring the Parameters of Low-Frequency Noise of Semiconductor Devices Under the Conditions of Mass Control

We solve the problem of increasing the reliability and efficiency of quality control for semiconductor devices and present the analysis of the conditions of measuring the power spectral density of low-frequency noise in semiconductor devices with spectra of the form G(f) ~ f–γ (γ is the parameter of shape of the spectrum) under the conditions of mass quality control. The measurement error of the power spectral density under given conditions of measurements strongly depends on the value of the parameter of form of the spectrum. We propose adaptive algorithms aimed at measuring the parameters of low-frequency noise in the cases of a given ultimate measurement error of power spectral density and a given duration of a single measurement. The proposed algorithms include the preliminary evaluation of the parameter of shape of the spectrum with subsequent measurements of the power spectral density of noise for the optimal bandwidth of the filter. The optimal bandwidth of the filter is established according to the results of preliminary evaluation of the parameter of shape of the spectrum. In both cases, we obtain estimates of the gain in a sense of the mean value over the set (ensemble) of controlled products. We also discussed the possibility of adaptive or cognitive adjustment of the parameters of measuring system in the control process based on the results of evaluation of sample means in the training sample.

The transition from generation–recombination noise in bulk semiconductors to discrete switching in small-area semiconductors

Scaling down the dimensions of Metal–Oxide–Semiconductor​ Field-Effect Transistors (MOSFETs) evinces discrete switching usually referred to as random telegraph signal (RTS). Such RTSs are usually attributed to the capture and emission of charge carriers by a single active trap located in an oxide layer. Machlup calculated the noise spectrum caused by these charge carriers based on probabilistic arguments. In this paper, we derive Machlup’s noise spectrum differently: the g–r​ noise is attributed to a random succession of elementary g–r pulses. This enables g–r bulk noise to be interpreted in terms of the numbers of traps. The transition from g–r bulk noise to discrete switching is found by reducing the number of traps to just one single active trap. The resulting g–r noise spectrum is shown to be equivalent to Machlup’s noise spectrum. The probability of an overlap of succeeding g–r pulses is calculated. Such an overlap is attributed to occupation of an empty single trap by an electron transferred from a neighboring trap. We simulate a g–r pulse train and find a large variety of patterns similar to those observed in MOSFETs. Excluding overlapping g–r pulses, the up-and-down distribution of succeeding g–r pulses is estimated.

Estimation of the lowest limit of 1/f noise in semiconductor materials

A lowest limit of 1/f noise in semiconductor materials has not yet been reported; we do not even know if such a lowest limit exists. 1/f noise in semiconductors has recently been brought into relation with 1/f noise in quantum dots and other materials. These materials exhibit on-off states which are power-law distributed over a wide range of timescales. We transfer such findings to semiconductors, assuming that the g-r process is also controlled by such on-off states. As a result, we obtain 1/f noise which can be expressed as Hooge's relation. Based on the intermittent g-r process, we estimate the lowest limit of 1/f noise in semiconductor materials. We show that this limit is inversely proportional to the dopant concentration; to detect the lowest limit of 1/f noise, the number of centers should be as small as possible. We also find a smooth dependence of 1/f noise and g-r noise on time.

Low-frequency charge noise in Si/SiGe quantum dots

Electron spins in silicon have long coherence times and are a promising qubit platform. However, electric field noise in semiconductors poses a challenge for most single- and multi-qubit operations in quantum-dot spin qubits. Here, we investigate the dependence of low-frequency charge noise spectra on temperature and aluminum-oxide gate dielectric thickness in Si/SiGe quantum dots with overlapping gates. We find that charge noise increases with aluminum oxide thickness. We also find strong dot-to-dot variations in the temperature dependence of the noise magnitude and spectrum. These findings suggest that each quantum dot experiences noise caused by a distinct ensemble of two-level systems, each of which has a non-uniform distribution of thermal activation energies. Taken together, our results suggest that charge noise in Si/SiGe quantum dots originates at least in part from a non-uniform distribution of two-level systems near the surface of the semiconductor.

Charge-particles transport in semiconductors characterized by a generalized Langevin equation with a fractional noise

From the view of intrinsic noise in semiconductors, the model of charge-particles transport in one-dimensional semiconductors described by a generalized Langevin equation (GLE) driven by a intrinsic fractional Gaussian noise is proposed in this paper. The analytical expression of the average charged particle velocity, the differential mobility, the conductivity of charge-particles, the two-time correlation function of the velocity fluctuation and the power spectral of total current density fluctuation have been derived. Furthermore, the model of motion for the charge-particle subjected to an electric field and a magnetic field governed by GLE is introduced. The expressions of mean values and variances of charged particle velocity, Fokker–Planck equation of charge-particle motion, the asymptotic behaviors of the relaxation functions have been obtained. Under the Hall effect, the Hall angle, the Hall coefficient, as well as the electrical resistivity also have been studied.

An Intermittent Generation–Recombination Process as a Possible Origin of 1/f Fluctuations in Semiconductor Materials

Inspired by the phenomenon of fluorescence intermittency in quantum dots and other materials, we introduce small off-states (intermissions) which interrupt the generation and recombination (= [Formula: see text]–[Formula: see text]) process in a semiconductor material. If the remaining on-states are power-law distributed, we find an almost pure 1/[Formula: see text] spectrum. Besides well-known [Formula: see text]–[Formula: see text] noise, we obtain two 1/[Formula: see text] noise components which can be attributed to the intermittent generation and recombination process. These components can be given the form of Hooge's relation with a Hooge coefficient [Formula: see text] describing the contribution of the generation and recombination process, respectively. Herein, the coefficients [Formula: see text] and [Formula: see text] describe impact of intermissions which in general are different for the generation and recombination process. The impact of [Formula: see text]–[Formula: see text] noise on 1/[Formula: see text] noise is comprised in the coefficient [Formula: see text] for the generation and [Formula: see text] for the recombination process. These coefficients are specified for an intrinsic and a slightly extrinsic semiconductor as well as for a semiconductor with traps; for the latter, the temperature dependence of 1/[Formula: see text] noise is also investigated. 1/[Formula: see text] noise is shown to be inversely related to the number of neutral and ionized [Formula: see text]-atoms rather than to the number of conduction electrons as defined in Hooge's relation. As a possible origin of 1/[Formula: see text] noise in semiconductors, electron–phonon scattering is suggested.

Bulk-impurity induced noise in large-area epitaxial thin films of topological insulators

We report a detailed study on low-frequency 1/f-noise in large-area molecular-beam epitaxy grown thin (∼10 nm) films of topological insulators as a function of temperature, gate voltage, and magnetic field. When the Fermi energy is within the bulk valence band, the temperature dependence reveals a clear signature of generation-recombination noise in the defect states in the bulk band gap. However, when the Fermi energy is tuned to the bulk band gap, the gate voltage dependence of noise shows that the resistance fluctuations in surface transport are caused by correlated mobility-number density fluctuations due to the activated defect states present in the bulk of the topological insulator crystal with a density of Dit=3.2×1017 cm−2 eV−1. In the presence of the magnetic field, noise in these materials follows a parabolic dependence, which is qualitatively similar to mobility and charge-density fluctuation noise in non-degenerately doped trivial semiconductors. Our studies reveal that even in thin films of (Bi,Sb)2Te3 with thickness as low as 10 nm, the internal bulk defects are the dominant source of noise.

The charge carrier capture–emission process – the main source of the low-frequency noise in homogeneous semiconductors

The possibility of determination of the number of localized capture centers of defects (relaxators) that cause low-frequency noise in a particular frequency range has been investigated. Here it is shown that a minimum number of relaxators is needed to generate 1/f type low-frequency noise only when relaxation times are arbitrarily distributed one-by-one in every two-octave range. The expression for estimation of the low-frequency noise level of the sample under test is presented. The presented expression for 1/f noise explains not only the noise level dependence both on the frequency and number of defects in the sample but also the observed noise intensity dependence on the mobility of free charge carriers. It is shown that the main source that causes low-frequency noise in homogeneous semiconductors is the charge carrier capture–emission process.

Nature of low-frequency noise in homogeneous semiconductors.

This report deals with a 1/f noise in homogeneous classical semiconductor samples on the base of silicon. We perform detail calculations of resistance fluctuations of the silicon sample due to both a) the charge carrier number changes due to their capture–emission processes, and b) due to screening effect of those negative charged centers, and show that proportionality of noise level to square mobility appears as a presentation parameter, but not due to mobility fluctuations. The obtained calculation results explain well the observed experimental results of 1/f noise in Si, Ge, GaAs and exclude the mobility fluctuations as the nature of 1/f noise in these materials and their devices. It is also shown how from the experimental 1/f noise results to find the effective number of defects responsible for this noise in the measured frequency range.

Social Noise: Generating Random Numbers from Twitter Streams

Due to the multiple applications of random numbers in computer systems (cryptography, online gambling, computer simulation, etc.) it is important to have mechanisms to generate these numbers. True Random Number Generators (TRNGs) are commonly used for this purpose. TRNGs rely on non-deterministic sources to generate randomness. Physical processes (like noise in semiconductors, quantum phenomenon, etc.) play this role in state of the art TRNGs. In this paper, we depart from previous work and explore the possibility of defining social TRNGs using the stream of public messages of the microblogging service Twitter as randomness source. Thus, we define two TRNGs based on Twitter stream information and evaluate them using the National Institute of Standards and Technology (NIST) statistical test suite. The results of the evaluation confirm the feasibility of the proposed approach.

Spin and valley noise in two-dimensional Dirac materials.

We develop a theory for optical Faraday rotation noise in two-dimensional Dirac materials. In contrast to spin noise in conventional semiconductors, we find that the Faraday rotation fluctuations are influenced not only by spins but also the valley degrees of freedom attributed to intervalley scattering processes. We illustrate our theory with two-dimensional transition-metal dichalcogenides and discuss signatures of spin and valley noise in the Faraday noise power spectrum. We propose optical Faraday noise spectroscopy as a technique for probing both spin and valley relaxation dynamics in two-dimensional Dirac materials.

1/f noise in semiconductor and metal nanocrystal solids

Electrical 1/f noise is measured in thin films of CdSe, CdSe/CdS, ZnO, HgTe quantum dots and Au nanocrystals. The 1/f noise, normalized per nanoparticle, shows no systematic dependence on the nanoparticle material and the coupling material. However, over 10 orders of magnitude, it correlates well with the nearest neighbor conductance suggesting some universal magnitude of the 1/f noise in these granular conductors. In the hopping regime, the main mechanism of 1/f noise is determined to be mobility fluctuated. In the metallic regime obtained with gold nanoparticle films, the noise drops to a similar level as bulk gold films and with a similar temperature dependence.