Leakage Current Fluctuations Research Articles

Switching dynamics in Al/InAs nanowire-based gate-controlled superconducting switch

The observation of the gate-controlled supercurrent (GCS) effect in superconducting nanostructures increased the hopes for realizing a superconducting equivalent of semiconductor field-effect transistors. However, recent works attribute this effect to various leakage-based scenarios, giving rise to a debate on its origin. A proper understanding of the microscopic process underlying the GCS effect and the relevant time scales would be beneficial to evaluate the possible applications. In this work, we observed gate-induced two-level fluctuations between the superconducting state and normal state in Al/InAs nanowires (NWs). Noise correlation measurements show a strong correlation with leakage current fluctuations. The time-domain measurements show that these fluctuations have Poissonian statistics. Our detailed analysis of the leakage current measurements reveals that it is consistent with the stress-induced leakage current (SILC), in which inelastic tunneling with phonon generation is the predominant transport mechanism. Our findings shed light on the microscopic origin of the GCS effect and give deeper insight into the switching dynamics of the superconducting NW under the influence of the strong gate voltage.

Schottky Diode Leakage Current Fluctuations: Electrostatically Induced Flexoelectricity in Silicon.

Nearly four decades have passed since IBM scientists pioneered atomic force microscopy (AFM) by merging the principles of a scanning tunneling microscope with the features of a stylus profilometer. Today, electrical AFM modes are an indispensable asset within the semiconductor and nanotechnology industries, enabling the characterization and manipulation of electrical properties at the nanoscale. However, electrical AFM measurements suffer from reproducibility issues caused, for example, by surface contaminations, Joule heating, and hard-to-minimize tip drift and tilt. Using as experimental system nanoscale Schottky diodes assembled on oxide-free silicon crystals of precisely defined surface chemistry, it is revealed that voltage-dependent adhesion forces lead to significant rotation of the AFM platinum tip. The electrostatics-driven tip rotation causes a strain gradient on the silicon surface, which induces a flexoelectric reverse bias term. This directional flexoelectric internal-bias term adds to the external (instrumental) bias, causing both an increased diode leakage as well as a shift of the diode knee voltage to larger forward biases. These findings will aid the design and characterization of silicon-based devices, especially those that are deliberately operated under large strain or shear, such as in emerging energy harvesting technologies including Schottky-based triboelectric nanogenerators (TENGs).

Physics-based modeling of surface potential and leakage current for vertical Ga2O3 FinFET

Gallium oxide (Ga2O3) is a promising ultra-wide bandgap material offering a large bandgap (>4.7 eV) and high critical electric fields. The increasing demand for electronic devices for high-power applications in electric automobiles, high-performance computing, green energy technologies, etc., requires higher voltages and currents with enhanced efficiency. Vertical transistors, such as fin-shaped field-effect transistors (FinFETs) have emerged to meet the growing need with improved current handling capabilities, reduced resistance, and enhanced thermal performance. However, to fully exploit the Ga2O3 power transistors, precise and reliable physics-driven models are crucial. Therefore, a comprehensive surface potential model has been developed in this work for a vertical Ga2O3 FinFET. The electric potential across the channel is explained by analyzing the two-dimensional (2D) Poisson equation employing parabolic approximation. Such a surface potential model is instrumental in determining the performance of the Ga2O3 FinFET as it affects the threshold voltage, the drain current, and fringing capacitance. Exploiting the surface potentials, a fringing capacitance model is derived which is crucial in analyzing the speed of the device in compact integrated circuits. In addition, statistical analysis of the Ga2O3 FinFET using the Monte Carlo simulation technique is performed to determine the leakage current fluctuation due to doping variations. The validation of the analytical model with experimental results confirms the effectiveness and prospects of the developed models in the rapid development and characterization of next-generation high-performance vertical Ga2O3 power transistors.

Adaptive Leakage Protection for Low-Voltage Distribution Systems Based on SSA-BP Neural Network

The fluctuation of normal leakage current has a great influence on the fixed-threshold leakage protector. To address this issue, this paper proposes an adaptive leakage protection method based on the sparrow search algorithm (SSA)-backpropagation (BP) neural network. Based on the analysis of the normal leakage current generation mechanism, this method uses the SSA optimized BP neural network to construct a prediction model of normal leakage current. By dividing the normal leakage range into several intervals and setting the corresponding action threshold, the action threshold of the interval is automatically selected in advance, based on the predicted value of the model, so as to realize the adaptive protection of the leakage current faults. Experiments have proved that the leakage protector can identify the leakage fault more sensitively and increase the ratio of the protector put into operation by predicting the development of normal leakage current and adjusting the protection action threshold in advance.

Design and Control of High Voltage Gain Interleaved Boost Converter for Fuel Cell Based Electric Vehicle Applications

The need for power is raising rapidly all across the world right now. This last period has seen a dramatic increase in the severity of global warming brought on by the earth's climate. Greenhouse gas emissions from customary fossil fuel-depend vehicles have risen to the forefront of environmental concerns as the number of cars on the road continues to rise. Pollution from traditional internal combustion engines is rising at an alarming rate. A growing number of people see renewable energy based techniques as ideal answers to the problems of rising fuel efficiency regulations and falling pollution levels. In recent years, interest in hydrogen's potential as a new energy vector has grown rapidly; this is because hydrogen can be converted to electric energy in a fuel cell (FC), making it a viable option for powering fuel cell electric vehicles (FCEV). In comparison to other fuel cell types, the working temperature range of a Proton Exchange Membrane Fuel Cell (PEMFC) makes it the best option for usage in automobiles. As the value of FC modules is rather low, a further action is necessary for interfacing with utility grids in FC-based power sources. Even though a traditional boost converter may increase the DC bus voltage from the FC to the necessary level by the inverter, doing so at a very high duty ratio reduces the converter's efficiency and effectiveness. In this study, we propose using high-gain interleaved DC-DC converters to fix this issue. To provide the electric vehicle's power train, this research introduces a radial basis function network (RBFN) with maximum power point tracking (MPPT) method for PEMFC. To determine the PEMFC's optimum operating point, the planned NN-MPPT method employs a RBFN. FCEVS require dc-dc converters with more switching frequencies and heavy voltage gains for propulsion. A three-phase high voltage-gain interleaved boost converter (HV-GIBC) is also developed for the FCEV method to achieve high voltage-gain. Power semiconductors are stressed by leakage current fluctuation and voltage fluctuations are lessened by the interleaving method. We evaluate the MATLAB/Simulink platform's Fuzzy Logic controller against the RBFN-based MPPT controller in an FCEV system's performance evaluation.

Three-Dimensional Mechanistic Modeling of Gate Leakage Current in High- κ MOSFETs

Gate leakage current is an issue for the reliability of modern high-$\ensuremath{\kappa}$ MOSFETs. Although various physical models describing both direct tunneling and trap-assisted contribution of leakage current have been presented in the literature, many of them treats traps in the dielectric as a continuum distribution in energy and position, and trap-to-trap transport of electrons has so far been mostly neglected or not treated three dimensionally. In this work, we present a mechanistic model for calculation of gate leakage current in high-$\ensuremath{\kappa}$ MOSFET multilayer stacks based on multiphonon trap-assisted tunneling theory, taking into account the intrinsic three-dimensional (3D) discreteness of traps in the dielectric. Our model can to a good approximation reproduce the experimental results at different dielectric thicknesses, gate voltages, temperatures, and different gate materials. We find that in realistic devices, the 3D trap-to-trap transport of electrons contributes a non-negligible part to the gate leakage current. This contribution is more pronounced at low-voltage device operations, which is important for low-power applications. We calculate the intrinsic fluctuation of gate leakage current due to positional and energetic disorder of traps in the dielectric, and conclude that positional disorder is more important than energetic disorder for realistic material parameters. The calculated gate leakage current depends sensitively on temperature, trap energy, and trap density. We provide a computationally efficient 3D master equation approach that enables 3D mechanistic simulation of ${10}^{3}$ traps on the order of minutes on a standard desktop computer.

Characterization of the Variable Retention Time in Dynamic Random Access Memory

To study the relationship between the original leakage current fluctuation and the detected variable retention time (VRT) from the retention test of dynamic random access memory (DRAM), we simulated the real procedure of the VRT measurement of DRAM. By investigating the results of the simulation, we proposed a new effective VRT measurement method based on the comparison between measurement and simulation. In addition, we investigated the characteristics of the VRT phenomenon in DRAM using the VRT characterization method developed in this study.

First-principles calculations of the band gap ofHfxSi1−xO2andZrxSi1−xO2alloys

A generalized quasichemical method and the cluster expansion approach are applied to calculate the band gap of amorphous ${\mathrm{Hf}}_{x}{\mathrm{Si}}_{1\ensuremath{-}x}{\mathrm{O}}_{2}$ and ${\mathrm{Zr}}_{x}{\mathrm{Si}}_{1\ensuremath{-}x}{\mathrm{O}}_{2}$ alloys within the pseudopotential based density-functional theory. The dependence of the band gap of ${\mathrm{Hf}}_{x}{\mathrm{Si}}_{1\ensuremath{-}x}{\mathrm{O}}_{2}$ and ${\mathrm{Zr}}_{x}{\mathrm{Si}}_{1\ensuremath{-}x}{\mathrm{O}}_{2}$ compounds on the molar concentration $x$ is computed to be nearly linear with small bowing parameter $b$. The mean-square deviation of the band gap, which defines the leakage current fluctuations, is explicitly calculated. The calculation of the internal stress in these compounds due to alloying yields a small value, which may be a reason for the small bowing in the band gap.

Light intensity-voltage correlations and leakage-current excess noise in a single-mode semiconductor laser

Semiconductor lasers are particularly well suited for the implementation of pump-noise suppression, yielding a reduction of the intensity noise in the laser. In this simple picture, the maximal amount of squeezing is equal to the quantum efficiency. However, experimental results on intensity noise reduction by pump-noise suppression are usually above this limit. This discrepancy suggests that additional noise sources must be involved. Here we successfuly interpret the full noise behavior of a single-mode laser diode far above threshold by considering two excess noise sources: the leakage current fluctuations across the laser and the Petermann excess noise. We have estimated the contribution of each noise source using the results of the correlations between the laser output intensity noise and the voltage fluctuations across the laser diode (light-voltage correlations) and obtained good agreement between our theory and experimental results.

Pre-breakdown leakage current fluctuations of thin gate oxide

Pre-breakdown leakage current fluctuations of thin gate oxide

A percolative model of soft breakdown in ultrathin oxides

The degradation of ultrathin oxide layers in the presence of a stress voltage is modeled in terms of two antagonist percolation processes taking place in a random resistor network. The resistance and leakage current fluctuations are studied by Monte Carlo simulations for voltages below the breakdown threshold. An increase of excess noise together with a noticeable non-Gaussian behavior is found in the pre-breakdown regime in agreement with experimental results.

Effect of gate leakage current on noise properties of AlGaN/GaN field effect transistors

The effect of the gate leakage current fluctuations on noise properties of AlGaN/GaN heterostructure field effect transistors (HFETs) has been studied in conventional HFET structures and in AlGaN/GaN metal-oxide-semiconductor heterostructure field effect transistors (MOS-HFETs). The comparison of the noise properties of conventional AlGaN/GaN HFETs and AlGaN/GaN MOS-HFETs fabricated on the same wafer, allowed us to estimate the contribution of the gate current noise to the HFET’s output noise. The effect of the gate current fluctuations on output noise properties of HFETs depends on the level of noise in the AlGaN/GaN HFETs. For the transistors with a relatively high magnitude of the Hooge parameter α∼10−3, even a relatively large leakage current Ig (Ig/Id∼10−3–10−2, where Id is the drain current) does not contribute much to the output noise. In HFETs with a relatively small values of α (α∼10−5–10−4), the contribution of the leakage current to output noise can be significant even at Ig/Id∼10−4–10−3. For such transistors, a very rapid increase of the 1/f noise with gate bias was observed. The differences in the noise behavior can be linked to the material quality of the AlGaN and GaN layers in different types of HFETs.

Soft breakdown fluctuation events in ultrathin SiO2 layers

When an ultrathin (<5 nm) oxide is subjected to electrical stress, several soft-breakdown events can occur prior to the final dielectric breakdown. After the occurrence of such failure events, the current–voltage (I–V) characteristic corresponds to the superposition of highly conductive spots and background conduction through the undegraded capacitor area. In this conduction regime, the application of a low constant voltage gives rise to large leakage current fluctuations in the form of random telegraph signal. Some of these fluctuations have been identified with ON/OFF switching events of one or more local conduction spots, and not with a modulation of their conductance. The experimental soft-breakdown I–V characteristics are shown to be better understood if the spot conduction is considered to be locally limited by the silicon electrodes and not by the oxide.

Current noise in thin film Al/Al 2O 3/Au sandwiches

Information is presented about the mode of electrical conductance in a Me/MeO/Me sandwich, a type of structure that has been subject to extensive earlier investigations. The dynamics of the electrical current fluctuations were determined for the Al/Al 2O 3/Au sandwich. Sandwiches with a 17 nm thick alumina interlayer were measured under vacuum conditions at room and 100 K temperatures. I–V characteristics of leakage current were found not symmetric and contain linear parts in In (I) ∼ V 1 2 plot. Power spectra of leakage current noise show relaxation processes at low frequencies which depend on applied voltage and temperature. Amplitude distribution of the leakage current fluctuations is Gaussian at low voltages but at higher voltages (6 V) contains local maxima. The appearance of the multilevel fluctuations corresponds to the voltage region when sandwich structures begin to be unstable and shows qualitative changes in a conduction mechanism. The state indicated by increasing noise power can result in irreversible structural changes—electroformation—when critical conditions are reached. The noise spectra measured at the two different temperatures show an important role of heat dissipation in the structure.

Improved Characteristics of p+-n Junctions formed by Excimer Laser Annealing with Low Temperature Pre-Annealing

P+-n diodes with shallow junctions less than 50 nm deep were formed utilizing single pulse excimer laser annealing. The diode characteristics and the crystallinity near the junctions was investigated and it was found that the characteristics were improved by annealing the sample at 600° C for 1 h prior to excimer laser annealing. A low leakage current density of ≤10 nA/cm2 under reverse bias and ideal I–V curves of 60 mV/dec. over 7 decades under forward bias were obtained. The average leakage current and the device to device leakage current fluctuation were both reduced when the pre-annealing was used. The crystallinity near the junction was investigated by cross sectional transmission electron microscopy (TEM).

Influence of AC Source Parameters on Flashover Characteristics of Polluted Insulators

The paper comprises a systematic experimental investigation into the influence of AC test source parameters on the leakage current pulses, voltage fluctuations and flashover voltages of polluted insulators. The test techniques include both salt-and clean-fog methods, while the test insulators comprise long-rod and cap and pin strings of different lengths as well as support columns.

Theory of Noise in Charge-Transfer Devices

The noise introduced into charge packets transferred through and stored in charge-transfer devices is calculated in a manner that includes all important relaxation, suppression, and correlation effects. First, the noise induced into each packet during each transfer phase from thermal, trapping, emission-current, and leakage-current fluctuations, whose statistics are nonstationary, and from clock-voltage fluctuations, whose statistics are stationary, is determined. Relaxation of the transferring charge to these fluctuations is found to suppress their size. Second, the accumulation (collecting) of the noise as each packet is transferred through the device is calculated neglecting the role of incomplete charge transfer. Attention is drawn to the significant differences between the collecting of storage-process noise, which is unsuppressed, transfer-process noise, whose spectral density is nearly totally suppressed at low frequencies, and modulation noise, which is nearly totally suppressed for digital and analog signals. Third, the role of incomplete charge transfer in suppressing the collecting of the noise is shown for digital signals and indicated for analog signals. We conclude with a numerical calculation of the maximum possible signal-to-noise ratio that can be expected from charge-transfer devices. The presentation is sufficiently general and detailed that, with a minimum of background in formal noise theory, one can use the approach to evaluate noise in many novel, solid-state devices.