Gate Current Research Articles

Anti-obesity and hypolipidemic effects of Morus alba- A review

The prevalence of obesity was worldwide increase in the last 60 years. Obesity represented one of the public health problems, it markedly increased the incidence of many diseases: fatty liver, type 2 diabetes, hypertension, ischemic heart diseases, sleep apnea, osteoporosis, dementia, tumors and many other disorders. Recent reviews showed that many medicinal plants possesses anti-obesity effect. In the current review, PubMed, Web Science, Science Direct, Research gate, Academia.edu and Scopus were searched to verify the hypolipidemic and anti-obesity activities of Morus alba.

Temperature impact on device characteristics of charge plasma based tunnel FET with Si0.5Ge0.5 source

In this work, the impact of temperature is investigated on the electrical characteristics of charge plasma-based doping-less double gate tunnel FET (DL-DG-TFET) with a low bandgap source material i.e., Si0.5Ge0.5. The influence of temperature (from 250 K to 450 K) is analysed on several performance parameters of the device such as bandgap, threshold voltage, SS, switching current ratio, ID-VGS, ID-VDS, gate current. The small change in energy bandgap with temperature reflects that device is minimally dependent on temperature. Temperature impact is significant on the sub-threshold region of transfer characteristics due to SRH recombination and trap-assisted tunnelling current. Insignificant variation of gate current with temperature signifies the better reliability of the device. Further, temperature effect is observed on analog parameters such as cut-off frequency, gate capacitance, trans-conductance, output conductance, power delay product (PDP). The minimal variation of analog parameters with temperature assures application of device in high-temperatures.

Temperature effects on the conducted emission of a high-side switch

Current source MOSFET gate drive circuits are used in many electronic equipment. These drivers allow supplying an optimized current profile to charge and discharge the gate of a power MOSFET. The reason, among others, to use such drivers is to generate a “trapezoidal output signal” with round corner in order to reduce the electromagnetic emissions characteristic of the equipment, especially in high frequency range. The current profile is usually determined by simulation, adjusted by measurement and finally fixed for the equipment which means that it cannot be changed once the equipment is used in its application. At the same time, during its life, the equipment, will experience environmental parameter variations such as temperature. This paper presents a study highlighting the effects of temperature on the conducted emission characteristics of high-side switch circuit embedding the driver circuit and the power transistor. This study has been done on a given circuit and should be enlarged on others to generalize the conclusions.

Influence of traps on the gate reverse characteristics of normally-off high-electron-mobility transistors with regrown p-GaN gate

The influence of traps on the reverse gate leakage has been studied for two kinds of normally-off high-electron-mobility transistors with regrown p-GaN gate. Different acceptor traps in the p-GaN/AlGaN/GaN junction dramatically impact carrier behaviors, affecting the leakage mechanisms. The reverse gate current of the normal devices with a low density of traps which located at E V + 0.6 eV is dominated by Poole–Frenkel process. For the abnormal devices, a high density of new traps have been confirmed with an energy level of ∼0.8 eV, resulting in a trap-assisted tunneling thus a relatively high reverse gate leakage.

Physics-Informed Neural Network for High Frequency Noise Performance in Quasi-Ballistic MOSFETs

A physics-informed neural network (PINN) model is presented to predict the nonlinear characteristics of high frequency (HF) noise performance in quasi-ballistic MOSFETs. The PINN model is formulated by combining the radial basis function-artificial neural networks (RBF-ANNs) with an improved noise equivalent circuit model, including all the noise sources. The RBF-ANNs are utilized to model the thermal channel noise, induced gate noise, correlation noise, as well as the shot noise, due to the gate and source-drain tunneling current through the potential barriers. By training a spatial distribution of the thermal channel noise and a Fano factor of the shot noise, underlying physical theories are naturally embedded into the PINN model as prior information. The PINN model shows good capability of predicting the noise performance at high frequencies.

Al0.7Ga0.3N MESFET With All-Refractory Metal Process for High Temperature Operation

Ultrawide bandgap Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.7</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</sub> N MESFETs with refractory Tungsten Schottky and Ohmic contacts are studied in 300-675 K environments. Variable-temperature dc electrical transport reveals large ON-state drain current densities for an AlGaN device: 209 mA/mm at 300 K and 156 mA/mm at 675 K in the ON-state (25% reduction). Drain and gate currents are only weakly temperature-dependent, suggesting potential for engineering temperature invariant operation. The ON-/ OFF-ratio is limited by OFF-state leakage through the gate, which is attributed to damage from sputter deposition. Future work using refractory metals with larger work functions that are deposited by electron beam deposition is proposed.

Electron irradiation effects on InP-based HEMTs with different gate widths

In this paper, the influence of electron irradiation on DC and RF characteristics of InP-based HEMTs with different gate widths were studied by irradiation experiment. The results show that the value of channel current (IDS) and transconductance (gm) are decreased for device with different gate width after electron irradiation, which is mainly due to the reduction of mobility in the channel by the irradiation-induced defects. However, the carrier concentration in the channel has a little change. Compared with the device with 100 μm gate width, IDS and gm of the device with 40 μm gate width were decreased by 1.5% and 3%. Meanwhile, the forward gate current decreased due to the increase of series resistance of gate contact caused by electron irradiation. The interface defects induced by electron irradiation induced the increase of the reverse gate current. Additionally, the current gain cut-off frequency (fT) and maximum oscillation frequency (fmax) were reduced by 19.8% and 10.9% for device with 40 μm gate width, and the fT and fmax were only reduced by 7.1% and 8.2% for device with 100 μm gate width. The experimental results indicate that designing a reasonable structure is an effective method to enhance the radiation resistance in InP-based HEMTs, and this method can also be utilized in other semiconductor devices.

Gating current noise produced by Brownian models of a voltage sensor

The activation of voltage-dependent ion channels is associated with the movement of gating charges, which give rise to gating currents. Although gating currents from a single channel are too small to be detected, analysis of the fluctuations of macroscopic gating currents from a population of channels allows a good guess of their magnitude. The analysis of experimental gating current fluctuations, when interpreted in terms of a rate model of channel activation and assuming sufficiently high bandwidth, is in accordance with the presence of a main step along the activation pathway carrying a charge of 2.3–2.4 e0. To give a physical interpretation to these results and to relate them to the known atomic structure of the voltage sensor domain, we used a Brownian model of voltage-dependent gating based on atomic detail structure, that follows the laws of electrodynamics. The model predicts gating currents and gating current fluctuations essentially similar to those experimentally observed. The detailed study of the model output, also performed by making several simplifications aimed at understanding the basic dependencies of the gating current fluctuations, suggests that in real channels the voltage sensor moves along a sequence of intermediate states separated by relatively low (<5 kT) energy barriers. As a consequence, crossings of successive gating charges through the gating pore become very frequent, and the corresponding current shots are often seen to overlap because of the relatively high filtering. Notably, this limited bandwidth effect is at the origin of the relatively high single-step charge experimentally detected.

Configurable gate driver for a stress test bench of newly developed discrete silicon power devices

Stress test system development is increasingly aimed at meticulous reliability and robustness evaluation for power semiconductors under application conditions as well as qualification purposes. Newly developed silicon (Si) power devices need further investigation in terms of potential new failure mechanisms. A double pulse tester is utilized as a test vehicle for studying hard switching related failure modes. However, setting up such a repetitive reliability test for multiple channels requires substantial manual labour. This paper proposes an open loop current source gate driver (CSGD) with adjustable gate voltage which can be software programmed, enabling an operator to set variable turn on/off speeds without hand-operated switching speed adjustment by gate resistors. The CSGD performance is assessed with various hard switching speeds in experiment and simulation for a discrete TO-247 MOSFET and IGBT respectively. Finally, additional considerations are proposed for faster switching so as to overcome the inherent nonlinearities and the CSGD output impedance effects.

Ultrasound‐gated computed tomography coronary angiography: Development of ultrasound transducers with improved computed tomography compatibility

Cardiovascular disease (CVD) is a leading cause of death worldwide, with coronary artery disease (CAD) accounting for nearly half of all CVD deaths. The current gold standard for CAD diagnosis is catheter coronary angiography (CCA), an invasive, expensive procedure. Computed tomography coronary angiography (CTCA) represents an attractive non-invasive alternative to CCA, however, CTCA requires gated acquisition of CT data during periods of minimal cardiac motion (quiescent periods) to avoid non-diagnostic scans. Current gating methods either expose patients to high levels of radiation (retrospective gating) or lead to high rates of non-diagnostic scans (prospective gating) due to the challenge of predicting cardiac quiescence based on ECG alone. Alternatively, ultrasound (US) imaging has been demonstrated as an effective indicator of cardiac quiescence, however, ultrasound transducers produce prominent streak artifacts that disrupt CTCA scans. In this study, a proof-of-concept array transducer with improved CT-compatibility was developed for utilization in an integrated US-CTCA system. Alternative materials were tested radiographically and acoustically to replace the radiopaque acoustic backings utilized in low frequency (1-4MHz) cardiac US transducers. The results of this testing were used to develop alternative acoustic backings consisting of varying concentrations of aluminum oxide in an epoxy matrix via simulations. On the basis of these simulations, single element test transducers designed to operate at 2.5MHz were fabricated, and the performance of these devices was characterized via acoustic and radiographic testing with micro-computed tomography (micro-CT). Finally, a first proof-of-concept cardiac phased array transducer was developed and its US imaging performance was evaluated. Micro-CT images of the developed US array with improved CT-compatibility were compared with those of a conventional array. Materials testing with micro-CT identified an acoustic backing with a measured radiopacity of 1008 HU, more than an order of magnitude lower than that of the acoustic backing (24,000 HU) typically used in cardiac transducers operating in the 1-4MHz range. When utilized in a simulated transducer design, this acoustic backing yielded a -6-dB fractional bandwidth of 57%, similar to the 54% bandwidth of the transducer with the radiopaque acoustic backing. The developed 2.5MHz, single element transducer based on these simulations exhibited a fractional bandwidth of 51% and signal-to-noise ratio (SNR) of 14.7dB. Finally, the array transducer developed with the acoustic backing having decreased radiopacity exhibited a 56% fractional bandwidth and 10.4dB single channel SNR, with penetration depth >10cm in phantom and in vivo imaging using the full array. The first attempt at developing a CT-compatible ultrasound transducer is described. The developed CT-compatible transducer exhibits improved radiographic compatibility relative to conventional cardiac array transducers with similar SNR, bandwidth, and penetration depth for US imaging, according to phantom and in vivo cardiac imaging. A CT-compatible US transducer might be used to identify cardiac quiescence and prospectively gate CTCA acquisition, reducing challenges associated with current gating approaches, specifically relatively high rates of non-diagnostic scans for prospective ECG gating and high radiation dose for retrospective gating.

Self-terminating contactless photo-electrochemical (CL-PEC) etching for fabricating highly uniform recessed-gate AlGaN/GaN high-electron-mobility transistors (HEMTs)

Contactless photo-electrochemical (CL-PEC) etching was used to fabricate recessed-gate AlGaN/GaN high-electron-mobility transistors (HEMTs). Self-termination of etching was observed during CL-PEC etching on an AlGaN barrier layer whose residual thickness had a uniform value of 6 nm overall on the same chip. After tetramethylammonium hydroxide post-treatment, the root-mean-square roughness of the etched surface was around 0.4 nm, which had smoothness comparable to that of the unetched surface. Recessed-Schottky HEMTs showed a positive shift in Vth, the suppression of drain leakage currents, and an improvement in the subthreshold-slope value as compared with planar-gate HEMTs. By applying a metal–insulator–semiconductor (MIS)-gate structure, the gate and drain leakage currents were significantly reduced, leading to an increased input dynamic range. Furthermore, the standard deviations (σ) of the Vth of CL-PEC-etched recessed-Schottky HEMTs and recessed-MIS HEMTs were very small, 5.5 and 16.7 mV, respectively. These results showed that the CL-PEC etching process is promising for the fabrication of recessed-gate AlGaN/GaN HEMTs having excellent uniformity for normally-off device operations.

Impact of gate current on the operational transconductance amplifier designed with nanowire TFETs

An Operational Transconductance Amplifier (OTA) designed with SiGe-source nanowire Tunnel-FETs is presented and compared with OTAs designed with Si nanowire (NW) TFETs and Si NW MOSFETs with and without the effect of gate current (IG). The devices were modeled using Verilog-A language through lookup tables obtained by experimental data and they were used to simulate the OTA circuits. It was observed that, when the IG is negligible, there is a trade-off between the DC open loop gain (AV0) and the gain-bandwidth product (GBW) of these circuits. The Si NW MOSFET OTA presented the lowest AV0 (52 dB) but the largest GBW (9.5 MHz). The largest gain was obtained by the Si NW TFET (97 dB) but it also presents the lowest GBW (30 kHz). The SiGe-source TFET stands in the middle, with an AV0 of 88 dB and a GBW of 715 kHz. However, when IG is not negligible and included in the model, the gain of the TFET OTAs decreases considerably, down to 38.3 dB in the case of the Si TFET and down to 52.6 dB in the case of the SiGe-source TFET. This decrease in gain is mostly caused by an alteration in the desired bias point in the second stage of the OTA due to the change of the output voltage and bias currents. This issue possibly can be mitigated by using circuit design strategies. Nevertheless, the SiGe-source TFET OTA is less impacted by the gate current than the Si TFET OTA and still presents a larger gain than the Si NW MOS OTA (52.6 dB against 50 dB) when the IG is considered.

A scalable large‐signal model with self‐heating effect based on a hybrid‐scaling rule for GaN high‐electron‐mobility transistors

AbstractIn this paper, a novel hybrid‐scaling rule for GaN high‐electron‐mobility transistors (HEMTs) scalable large‐signal model with self‐heating effect is proposed. Due to the complex parasitic characteristics of large gate‐width GaN HEMT devices, nonlinear scaling rules are used to consider the dependence of the extrinsic inductances, extrinsic resistances, and thermal resistance on the gate width. In addition, a drain‐source current model and gate capacitance models are proposed to improve the accuracy of traditional Angelov model. A one stage resistor‐capacitor network is attached in the current model to characterize self‐heating effect. Therefore, a scalable large‐signal model based on a hybrid‐scaling rule is presented for the first time. Compared with traditional linear scalable model, the proposed model has a good prediction for multi‐bias S‐parameters and direct current (DC) I‐V curves of different size devices, and can also significantly improve the fitting degree of S22 parameter at high frequency. Moreover, the proposed scalable model shows a good prediction of large‐signal characteristics for large size GaN HEMT devices.

Accurate determination of threshold voltage shift during negative gate bias stress in 4H-SiC MOSFETs by fast on-the-fly method

The threshold voltage shift in NO-annealed 4H-SiC MOSFETs during negative gate bias stress was investigated with a fast on-the-fly method for p-channel devices while considering the stress–time dependence of the slope of the drain current–gate voltage characteristics. With the proposed method, the threshold voltage shift was accurately measured over a wide time range from hundreds of nanoseconds. The negative threshold voltage shift exhibited power-law time dependence at room temperature and logarithmic time dependence at 423 K, suggesting that interface trap generation is observable at room temperature and thermally-assisted hole trapping in SiO2 dominates at high temperatures.

The voltage sensor is responsible for ΔpH dependence in Hv1 channels

The dissipation of acute acid loads by the voltage-gated proton channel (Hv1) relies on regulating the channel's open probability by the voltage and the ΔpH across the membrane (ΔpH = pHex - pHin). Using monomeric Ciona-Hv1, we asked whether ΔpH-dependent gating is produced during the voltage sensor activation or permeation pathway opening. A leftward shift of the conductance-voltage (G-V) curve was produced at higher ΔpH values in the monomeric channel. Next, we measured the voltage sensor pH dependence in the absence of a functional permeation pathway by recording gating currents in the monomeric nonconducting D160N mutant. Increasing the ΔpH leftward shifted the gating charge-voltage (Q-V) curve, demonstrating that the ΔpH-dependent gating in Hv1 arises by modulating its voltage sensor. We fitted our data to a model that explicitly supposes the Hv1 voltage sensor free energy is a function of both the proton chemical and the electrical potential. The parameters obtained showed that around 60% of the free energy stored in the ΔpH is coupled to the Hv1 voltage sensor activation. Our results suggest that the molecular mechanism underlying the Hv1 ΔpH dependence is produced by protons, which alter the free-energy landscape around the voltage sensor domain. We propose that this alteration is produced by accessibility changes of the protons in the Hv1 voltage sensor during activation.

Ultraviolet light stimulated water desorption effect on emission performance of gated field emitter array

The performance of silicon gated field emission arrays (GFEAs) was characterized before and after ultraviolet (UV) light exposure. Emission and gate leakage currents were measured on 1000 × 1000 tip arrays by sweeping the gate voltage to 40 V DC with a fixed DC collector voltage of 100 V DC. UV light exposure was used to desorb water molecules from the GFEA surfaces. It was found that, before UV exposure, the gate current was 6 mA at 40 V, whereas after 70 min of UV exposure, the gate current decreased to 0.46 mA, indicating a more than ten times reduction in leakage current between the gate and the emitter. Similarly, the observed collector current was 94 μA at 40 V before exposure, and after UV exposure, the collector current increased to 1.33 mA, indicating an improvement of more than 14 times. During the experiments with UV light, residual gas analyzer measurements showed that the partial pressure for water increased by greater than ten times after 60 min of exposure and then decreased by 1 order of magnitude after 100 min of exposure. The emission and leakage current changes remained even after turning off the UV lamps for several tens of minutes; however, upon the exposure to the atmosphere for a few days, those changes reversed. The enhancement could again be observed after additional UV exposure indicating that the adsorbates (mainly water along with others) on the surface affected the leakage between gate and emitter and field emission. Based on analysis of the IV characteristics before and after UV exposure, the work function of the emitter surfaces increases while the portion of the array tips that emits expands resulting in a decrease in the calculated array tip sharpness as duller tips now emit.

Gamma radiation effects on diamond field-effect biosensors with fibroblasts and extracellular matrix

Due to high biocompatibility, miniaturization, optical transparency and low production cost together with high radiation hardness the diamond-based sensors are considered promising for radiation medicine and biomedicine in general. Here we present detection of fibroblast cell culture properties by nanocrystalline diamond solution-gated field-effect transistors (SG-FET), including effects of gamma irradiation. We show that blank nanocrystalline diamond field-effect biosensors are stable at least up to 300 Gy of γ irradiation. On the other hand, gate current of the diamond SG-FET biosensors with fibroblastic cells increases exponentially over an order of magnitude with increasing radiation dose. Extracellular matrix (ECM) formation is also detected and analyzed by correlation of electronic sensor data with optical, atomic force, fluorescence, and scanning electron microscopies.

Numerical Study of Two HEMTs, AlGaN and InGaN, by Sharing the Drain Area for Power Application

In this paper we simulate a high electron mobility transistor structure of two HEMTs, by sharing the drain, with the using Silvaco-Tcad software. Our two HEMTs AlGaN and InGaN, on H4-SiC substrate and 50 nm gates length shows a very good scalability in different applications. It demonstrates a drain current of about 991.4 mA, a maximum transconductance of 859.1 ms/mm at Vds = 3V, a cut-off frequency of 115.6 GHz, a maximum oscillation frequency of 168.8 GHz, a drain-induced barrier lowering (DIBL) = 40 mV/V, a sub-threshold swing of 130 mV/dec, an On/Off current ratio higher than 6.82 × 107 and a leakage gate current of 2 × 10−8 A.

The Joy of Markov Models—Channel Gating and Transport Cycling Made Easy

ABSTRACT The behavior of ion channels and transporters is often modeled using discrete state continuous-time Markov models. Such models are helpful for the interpretation of experimental data and can guide the design of experiments by testing specific predictions. Here, we describe a computational tool that allows us to create Markov models of chosen complexity and to calculate the predictions on a macroscopic scale, as well on a single-molecule scale. The program calculates steady-state properties (current, state probabilities, and cycle frequencies), deterministic macroscopic and stochastic time courses, gating currents, dwell-time histograms, and power spectra of channels and transporters. In addition, a visual simulation mode allows us to follow the time-dependent stochastic behavior of a single channel or transporter. After a basic introduction into the concept of Markov models, real-life examples are discussed, including a model of a simple K+ channel, a voltage-gated sodium channel, a 3-state ligand-gated channel, and an electrogenic uniporter. In this manner, the article has a modular architecture, progressing from basic to more advanced topics. This illustrates how the MarkovEditor program can serve students to explore Markov models at a basic level but is also suited for research scientists to test and develop models on the mechanisms of protein function.

In Operando Angle‐Resolved Photoemission Spectroscopy with Nanoscale Spatial Resolution: Spatial Mapping of the Electronic Structure of Twisted Bilayer Graphene

To pinpoint the electronic and structural mechanisms that affect intrinsic and extrinsic performance limits of 2D material devices, it is of critical importance to resolve the electronic properties on the mesoscopic length scale of such devices under operating conditions. Herein, angle‐resolved photoemission spectroscopy with nanoscale spatial resolution (nanoARPES) is used to map the quasiparticle electronic structure of a twisted bilayer graphene device. The dispersion and linewidth of the Dirac cones associated with top and bottom graphene layers are determined as a function of spatial position on the device under both static and operating conditions. The analysis reveals that microscopic rotational domains in the two graphene layers establish a range of twist angles from 9.8° to 12.7°. Application of current and electrostatic gating lead to strong electric fields with peak strengths of 0.75 V/μm at the rotational domain boundaries in the device. These proof‐of‐principle results demonstrate the potential of nanoARPES to link mesoscale structural variations with electronic states in operating device conditions and to disentangle such extrinsic factors from the intrinsic quasiparticle dispersion.