Lateral Electric Field Research Articles

Investigating two-stage degradation of threshold voltage induced by off-state stress in AlGaN/GaN HEMTs

In this work, a two-step degradation phenomenon in D-mode Si3N4/AlGaN/GaN metal–insulator–semiconductor-high electron mobility transistors is discussed systematically. During off-state stress, threshold voltage shifts positively for a short duration, and is followed by a negative shift. In contrast, the off-state leakage continues to decrease throughout the entire stress. Results of varied measurement conditions indicate that carrier trapping at different regions dominates this phenomenon. It is interesting that under a large lateral electric field, electron–hole pairs are generated and will then be trapped at the gate dielectric layer. Furthermore, when increasing the stress temperature, impact ionization due to carriers from the gate electrode becomes more severe. Finally, devices with different gate insulator thicknesses are performed to verify the physical model of the degradation behavior.

Pressure-driven water flow through a carbon nanotube controlled by a lateral electric field

Tuning the water flow through nanochannels provides a key to many physicochemical phenomena, such as energy harvesting, desalination, biosensors and so on.

Compact Liquid Analyzer Based on a Resonator with a Lateral Excitation Electric Fieldcompact Liquid Analyzer Based on a Resonator with a Lateral Excitation Electric Field

Compact Liquid Analyzer Based on a Resonator with a Lateral Excitation Electric Fieldcompact Liquid Analyzer Based on a Resonator with a Lateral Excitation Electric Field

A lateral electric field inhibits gel-to-fluid transition in lipid bilayers.

We report evidence of lateral electric field-induced changes in the phase transition temperatures of lipid bilayers. Our atomic scale molecular dynamics simulations show that a lateral electric field increases the melting temperatures of DPPC, POPC and POPE bilayers. Remarkably, these shifts in the melting temperatures are only induced by lateral electric fields, and not normal electric fields. This mechanism could provide new mechanistic insights into lipid-lipid and lipid-protein interactions in the presence of endogenous and exogenous electric fields.

Rheology-modulated alterations in electro-magneto-hydrodynamic flows in a narrow cylindrical capillary: Contrasting trends in high and low surface charge limits.

We investigate electrokinetic transport of power-law fluids in a narrow cylindrical capillary in the presence of a transverse magnetic field. The governing equations including the full Poisson-Boltzmann equation and the Cauchy momentum equation with power-law constitutive behavior are solved numerically, without being restrictive to low surface potential limits. The influence of the power-law index, wall zeta potential, relative strength of electromagnetic force over viscous force (as represented by the Hartmann number), and the lateral electric field strength on the variation of the volumetric flow rate is analyzed. Our results reveal a significant augmentation in the net-throughput beyond the traditionally explored low surface-charge limits, especially for shear-thinning fluids, defying the established notions. These fundamental theoretical premises may act as essential precursors towards developing deeper insights on fluidic transport bio-nanopores under electro-magneto- hydrodynamic influences.

Transient Current Enhancement in MIS Tunnel Diodes With Lateral Electric Field Induced by Designed High-Low Oxide Layers

In this work, the steady-state and transient behavior of the metal–insulator–semiconductor tunnel diodes with designed high-low (H/L) oxide layers were studied, by performing experiments and TCAD simulations. The H/L oxide layers were formed by thickening the oxide around the gate edge while still in a tunneling-transparent thickness. This could reduce the leakage or tunneling current at reverse bias by decreasing the minority carrier density near the gate edge via the induced lateral electric field caused by H/L oxides. The characteristics of devices with various designed parameters were under investigation to discover the necessary conditions for the tunneling current reduction. Due to the leakage current reduction, the enhancement of transient current was found out, accompanied with enlarged transient capacitance change. Steady-state and transient simulation could help to confirm the observed phenomenon and also illustrated the existence of lateral electron current flow that reduced the minority carrier density near the gate edge at reverse bias. A memory operation using the H/L device was demonstrated. The read current at 120 ms improved more than an order of magnitude in current window with respect to planar. The stable performance under endurance testing made the H/L device a possible future volatile memory application.

Microbial acoustic sensor test-system based on a piezoelectric resonator with a lateral electric field for kanamycin detection in liquid

A microbial test-system for real-time determination of low/residual concentrations of kanamycin in a liquid without the need for special labels is presented. The main element of the system was a piezoelectric resonator excited by a lateral electric field based on an X-cut lithium niobate plate 0.5 mm thick with two rectangular electrodes on one side. On the other side of the resonator, there was a 1.5 ml liquid container. As a sensory element we used Escherichia coli B-878 microbial cells, which are sensitive to kanamycin. For measurement 1 ml of this cells suspension was placed in a liquid container and then the test liquid in the amount of 2 μl containing kanamycin was added. The change in the real part of the electrical impedance of the resonator before and after the test liquid addition was used as an analytical signal which indicated the presence of kanamycin. The lower limit of determination of kanamycin turned out to be 1.0 μg/ml with an analysis time of 10 min. The test-system allows to detect kanamycin in the presence of such antibiotic as ampicillin and polymixin.

Electrical properties of high permittivity epitaxial SrCaTiO3 grown on AlGaN/GaN heterostructures

Epitaxial integration of perovskite oxide materials with GaN has unlocked the potential to improve functionality and performance in high-power RF and power-switching applications. In this work, we demonstrate structural and electrical properties of high dielectric constant Sr1−xCaxTiO3 epitaxial layers grown on AlGaN/GaN/4H-SiC high-electron-mobility transistor structures with compositions ranging from x = 0 to x = 0.53 and oxide film thicknesses ranging from 7 to 126 nm. We show (111) orientation in the SrCaTiO3 (SCTO) thin films using a 1 nm (100) TiO2 buffer layer grown by RF-plasma-assisted oxide molecular beam epitaxy. Current–voltage measurements show up to 5 orders of magnitude reduced leakage with SCTO films when compared to Schottky contacted samples. Capacitance–voltage measurements show minimal hysteresis, an extracted dielectric constant (κ) as high as 290, and a fixed positive interface charge density of 2.38 × 1013 cm−2 at the SCTO/AlGaN interface. The direct integration of the SCTO layer does not significantly affect the two-dimensional electron gas (2DEG) density or the channel mobility with the 2DEG density as a function of SCTO thickness having good agreement with 1D Poisson–Schrödinger simulations. RF characterization of interdigitated capacitors using the SCTO films on unintentionally doped GaN/SiC shows that the films maintain their high κ into microwave frequencies and only exhibit a slight reduction in κ with increased lateral electric fields. These results demonstrate that the integration of a high-κ oxide with GaN can potentially improve electric field management in RF high-electron-mobility transistors and increase the device breakdown voltage without significant degradation to channel transport properties.

Defect-engineering-enhanced electrical manipulation of anisotropic excitons in two-dimensional ReS2

Engineering the photoluminescence (PL) properties, such as emission peaks, intensity, and lifetime, is highly desirable for widespread applications. Electric control is a facile and feasible method, and electrical manipulation of the PL properties with a high efficiency becomes increasingly important. ReS2 has excellent environmental stability, distinctive interlayer decoupling, and strong anisotropic properties. Herein, taking ReS2 as a prototype material, we propose a novel strategy to enhance electrical control of anisotropic excitons in ReS2 by defect engineering. Sulfur vacancies have been introduced controllably by mild argon plasma treatment, and contribute to the anisotropic defect-related exciton emission whose polarization direction is almost the same as those of the excitons along the Re–S atomic chains. However, the conversion from the neutral excitons to the defect-related excitons significantly modulate the radiation recombination behavior under a lateral electric field. The defect-engineering-enhanced electrical manipulation of anisotropic excitons paves the way towards an exciton engineering in new 2D electronic and optoelectronic devices.

Giant Enhancement of Excitonic Electro-optic Response in Trap-Reduced Organic Transistors

Organic field-effect transistors (FETs) exhibit excellent switching characteristics when they involve trap-eliminated semiconductor interfaces with highly hydrophobic gate dielectric layers. In this study, we investigate the excitonic electro-optic response by delocalized carrier accumulation at the trap-eliminated interfaces of pentacene single-crystal FETs. We find that gate-modulation (GM) imaging, which sensitively visualizes the variation in optical microscope images between the gate-on and gate-off states, exclusively reveals the unique enhancement of electro-optic response under the application of drain voltages (${V}_{d}$). The ${V}_{d}$-unbiased GM image exhibits a uniform spatial distribution, which is consistent with the accumulated carrier density in the channel. In contrast, the ${V}_{d}$-biased GM image presents a peculiar spatial distribution with fairly sharp increases around the edges of the source and drain electrodes. Furthermore, the following intriguing features are observed: (1) The sharp increase in the GM signal distribution around the electrode edge is similar to the lateral electric field distribution as measured by Kelvin probe force microscopy, and (2) the GM spectra, extracted from the respective GM images measured at different wavelengths, present a second-derivative-like shape that implies the broadening of exciton absorption. Based on these observations, we investigate the origin of this unique effect in terms of the enhanced violation of exciton coherence by delocalized carrier accumulations under drain bias. The gate-induced holes that are weakly bound to shallow traps should be detrapped by lateral electric fields, which eventually generate valence band holes and thus enhance the electro-optic response. These findings should elucidate the spatial coherence of the molecular excitons that are responsible for the various unique photoelectric characteristics of organic electronic devices.

Heat transfer model for electrochromatography in transverse electric field

Joule heating caused by electric currents is a major problem in scale-up electrochromatography. Here, to predict the temperature effects of lateral electric field electrochromatography and the process conditions required, a mathematical heat transfer model was established, which took into account the physical characteristics, including the electrical conductivity, of the porous medium and the ceramic plate in the gel chamber. The temperatures calculated using this model were within 4 °C of the experimentally measured results. For the lateral enlargement simulation of short columns (4 cm), it was found that when the width was enlarged to > 3 cm, the outlet temperature on the center line did not increase with increasing width. The electric field strength of 1700 V/m was maintained by increasing current strength according to the column size; further, when the gel chamber was enlarged to 0.075 × 0.075 × 0.1 m3, its internal temperature can be controlled within 16 °C under certain operating conditions, and an electric field strength of 1700 V/m can be obtained in the gel chamber.

The Impact of Contact Position on the Retention Performance in Thin‐Film Ferroelectric Transistors

Here, the simulation of the physical fields in an n‐type ferroelectric thin‐film transistor (FeTFT) with a bottom contact bottom‐gate configuration is demonstrated. In the off‐state, the intensity of the lateral electric field in the space charge region near the edge of the drain electrode is several times higher than the coercive field of the ferroelectric film, pinning the direction of polarization near the drain electrode along the channel. While the FeTFT switches from off‐state to on‐state, the vertical component of polarization near the drain edge is stronger than other parts near the channel. This enhances the depolarization field in this area so that the retention performance of the on‐state is worse than the off‐state. These results and methods benefit FeTFTs and are also valuable for floating‐gate memory and light‐emitting field‐effect transistors.

Hot electron effects in AlGaN/GaN HEMTs during hard-switching events

This work contains an investigation of hot-electrons effects in GaN transistors during a hard-switching event by means of wafer-level measurements and TCAD mixed-mode hydrodynamic simulations. The latter reveals the presence of hot electrons at the passivation/barrier interface during commutation. Trapping in this location can explain the measured on-state resistance increase during switching operation and leads to a redistribution of the lateral electric field in the two-dimensional electron gas, which in return modulates the hot electron injection process.

Intrinsic Mechanism of Mobility Collapse in Short MOSFETs

The mobility degradation with channel length is examined from the viewpoint of electrostatic effects that alter not only the threshold voltage but also the transport properties. Even operated at low drain voltage, short MOSFETs are subject to a strong lateral electric field present over a significant portion of the channel. The lateral field, responsible for threshold voltage roll-off, causes a local degradation in the velocity and mobility of electrons and holes. The low-mobility regions located near the source and drain tend to merge in short devices, giving rise to an ineluctable mobility collapse that compromises the benefit of downscaling. This mechanism is fundamental and universal as it applies to all kinds of MOSFETs. A model of mobility collapse, totally different from existing theories, is proposed together with supportive numerical simulations.

Stability of Excited Exciton States in Semiconductor Quantum Dots Under a Lateral Electric Field

The effect of the lateral electric field (LEF) on the excited and ground state stability of an exciton ([Formula: see text]) confined in a parabolic cylindrical quantum dot (QD) was estimated in this study. The calculation was performed in the framework of single-band effective mass theory using a variational approach. Our results revealed that the ground state binding energy of [Formula: see text] decreases with increasing the cylindrical QD radius until the exciton stability is lost at moderate LEF strength. By increasing the LEF strength, the excited heavy-hole ([Formula: see text]) can create an excited state [Formula: see text] or excited state [Formula: see text] of [Formula: see text], and the results indicate that the first state is more stable. In contrast, when an excited electron ([Formula: see text]) combines with an excited hole ([Formula: see text]) or unexcited hole ([Formula: see text]), it contains no split excited states for [Formula: see text] with less binding energy than the state [Formula: see text]. Comparing our previous results of donor impurity [Formula: see text] with [Formula: see text], we found that [Formula: see text] has a more stable ground state than [Formula: see text]. Moreover, the excited [Formula: see text] states are more stable than the excited states of [Formula: see text]. The quantum Stark shift (QSS) of the light- and heavy-hole exciton energy was explored, and a blue-shifted and quadratic QSS was observed. In contrast, for single particles (electron, heavy-hole and light hole), a red-shifted and linear QSS was observed.

A formula for the admittance of laterally excited bulk wave resonators (XBARs)

The recently invented laterally excited bulk wave resonators (XBARs) demonstrate outstanding parameters suitable for the design of low loss filters for the fifth generation of mobile phones. The operation of XBARs can be interpreted as an excitation of anti-symmetric Lamb mode A1 by the interdigital transducer. However, it can also be seen as the generation of fundamental plate resonances in a set of parallelly connected quasi-independent resonators, excited by a lateral electric field created by narrow electrodes with alternating polarity. By exploiting this latter interpretation, we propose a formula for the admittance of multi-layered membranes, including the main piezoelectric layer of suitable orientation and different additional dielectric layers on both sides of the membranes. The structure can be asymmetric and the excitation of all shear wave thickness resonances, not only with odd numbers, is described. The formula can be used for the one-dimensional modelling and optimisation of XBARs and the estimation of the resonance frequency dependence on the deposited trimming thin layers.

Dual-plasmon-induced photocatalytic performance enhancement in Au-PbS-CdS nanodumbbells with double Au caps on the ends

In this paper, Au-PbS-CdS nanodumbbells (NDs) with double Au caps on the ends have been synthesized by a simple three-step wet-chemical method. The results show that, a L-SPR induced lateral electric field distribution around this hybrid can be tactfully achieved by adjusting the size of Au caps and their distance, and the dual-plasmon-induced wide spectral coupling between metal and semiconductor can also be observed. Also, the intimate and multi-interface contacts (such as PbS-CdS, Au-PbS and Au-CdS) in these heterostructures provide multiple channels for high-speed photogenerated charge carrier transfer. These will provide a new possibility for high efficiency utilization of solar energy. Subsequently, we have further evaluated the photocatalytic performance of the designed Au-PbS-CdS ND photocatalysts through photocatalytic H2 generation and degradation tests of rhodamine B. The H2 generation rate of the photocatalyst was measured to be 6.31 times higher than that of the mixture of nanoparticles (NPs) (nearly 1.34 times that of core-shell nanorod (NRs) structures). The corresponding rate constant of RhB photodegradation is respectively about 2.35 and 6.41 times that of the NRs and mixture of pure semiconductor NPs. Specifically, the photocatalytic activities of Au-PbS-CdS ND photocatalysts increase with Au caps enlarging. Our results demonstrate that Au-PbS-CdS NDs with double Au caps on the end possess more outstanding visible/NIR-light-driven photocatalytic actives.

Effect of a Conducting Film of Finite Thickness Deposited on a Resonator with a Lateral Electric Field on Its Characteristics

Effect of a Conducting Film of Finite Thickness Deposited on a Resonator with a Lateral Electric Field on Its Characteristics

Determination of a Microbial Cells in Their Interaction with Phage Mini-Antibodies by the Sensor Based on a PZT Resonator with a Lateral Electric Field

Determination of a Microbial Cells in Their Interaction with Phage Mini-Antibodies by the Sensor Based on a PZT Resonator with a Lateral Electric Field

A Novel Technique for Determination of Residual Direct-Current Voltage of Liquid Crystal Cells with Vertical and In-Plane Electric Fields

Generation of residual direct-current (DC) voltage (VrDC) induces serious image sticking of liquid crystal displays (LCDs). In this study, a novel technique to determine the VrDC of LC cells is proposed. We found that the VrDC could be determined from a current-voltage (I-V) curve obtained by the application of triangular voltage. In the case of a vertically aligned twisted nematic (VTN) mode LC cell, where a vertical electric field is applied, the I-V curve shows maximum and minimum current peaks owing to rotation of an LC director, and the VrDC is able to be determined from an average value of the two peaks. On the other hand, in the case of a fringe field switching (FFS) mode LC cell, where an in-plane (lateral) electric field is applied from comb electrodes, the current peaks derived from the rotation of the LC director do not appear. Therefore, we could not adopt the same way with that of the VTN mode LC cell. However, we found that there were two minimum current peaks derived from minimum capacitances of the FFS mode LC cell, and could determine the VrDC by using these two current peaks. The proposed technique would be useful for the evaluation of the VrDC of the LCDs, where the electric field is applied both vertically and laterally.