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Abstract Surface charges accumulated on solid insulating materials in electrical apparatuses and electronic devices could distort the initial electric field and severely damage the insulation performance. Accurate transient surface charge measurement is critical to determine the mechanisms of charge transport and flashover occurrence, and estimate surface insulation strength under high voltage. The measurement technique based on the Pockels electro‐optic effect is considered as the only approach for 2‐D dynamic charge distribution behaviour so far, and it has good capability to avoid original electric field distortion caused by conventional methods featured by metal probes. This paper reviews recent progress of the non‐invasive dynamic surface charge measurement systems on the Pockels technique. We focus especially on typical systems with transmitting and reflecting configurations and the frequently used fast inversion algorithms. It can be inferred that higher spatial‐temporal resolution, higher signal‐to‐noise ratio, and better compatibility for both transparent and opaque materials are the future development trends, which greatly depend on multiple technological breakthroughs at impact‐resistant electro‐optic crystals, advanced high‐speed photography and high‐performance inversion algorithms. In addition, the recent studies on transient behaviour of surface discharge, together with the present limitation and future prospects are discussed. It is expected that more ideas will be inspired in transient surface charge measurement by the Pockels technique and other relevant electro‐optic methods.

When two HVDC transmission lines run across, because of the interaction between the two lines, the maximum ground-level total electric field is not a simple superposition of the maximum ground-level total electric field generated when the two lines exist alone. This paper presents an approximate method to use the maximum ground-level total electric field when only the lower line exists as the maximum ground-level total electric field when two lines run across. Here, the 3D method of characteristics has been improved to make it suitable for structure of two lines intersected at an angle using a method of coordinate transformation. The 3D method of characteristics is used to calculate the theoretical maximum electric field when the two lines run across. The 2D FEM is used to calculate the approximate maximum electric field when only the lower line exists. The approximate results and theoretical results are compared for line structures of ±800 kV line runs across ±800 kV line, ±660 kV line, and ±500 kV line at any intersection angle. The approximate errors are < ±10%, which can meet the engineering requirement.

With the development of high-voltage direct-current (HVDC) transmission projects, the issue of electromagnetic compatibility has become more and more severe, especially the synthetic ion flow electric field. The DC electric field is inseparable from the equipment insulation, the safety of the system operation, and effects on organisms nearby. The measurement of the synthetic electric field of ion flow has been a major difficulty due to the influence of ion currents and distorted field. A differential electric field sensor for measuring the synthetic electric field is proposed. The calibration method and the experimental device for the measurement of the air synthetic electric field of ion flow are presented. Calibration experiments show that the calibration method is practical and effective, and the test result from the sensor is in good agreement with the theoretical value. The experiments in the library show the validity of the calibration method and the excellent performance of the sensor.

The decomposition of cellulose plays a critical role in composting agricultural wastes. In this study, the electric field-assisted biodegradation (EAB) process was employed to degrade cellulose. To assess the effect of the electric field, we examined the physicochemical properties of cellulose and the physiological state of microorganisms. The results showed that the degradation rate of cellulose in EAB was significantly higher than that in the biodegradation process alone. Specifically, the degradation rate of cellulose increased with increasing electric field intensity, with a 2.57-fold increase observed after 24 h when the electric field intensity was 2 V/cm. Compared to the biodegradation process, EAB resulted in a greater reduction in cellulose crystallinity. The cellulose surface became rougher and more wrinkled in EAB, which facilitated bacterial adherence. Furthermore, when an external electric field with an intensity of 2 V/cm was applied, the microbial ATP activity showed a 6-fold increase compared to that without any external electric field. This implies that the microbial metabolic activity could be enhanced by utilizing a low voltage external electric field. Additionally, the electric field was observed to increase the permeability of the bacterial cell membrane by 5%27%, which can facilitate the transportation of substances into the cells. [ABSTRACT FROM AUTHOR]

By using two-dimensional particle-in-cell simulations, we demonstrate high-flux dense positrons generation by irradiating an ultra-intense laser pulse onto a tapered hollow target. By using a laser with an intensity of 4 ×1023W/cm², it is shown that the Breit-Wheeler process dominates the positron production during the laser-target interaction and a positron beam with a total number >1015 is obtained, which is increased by five orders of magnitude than in the previous work at the same laser intensity. Due to the focusing effect of the transverse electric fields formed in the hollow cone wall, the divergence angle of the positron beam effectively decreases to ~15° with an effective temperature of ~674 MeV. When the laser intensity is doubled, both the positron flux (>1016) and temperature (963 MeV) increase, while the divergence angle gets smaller (~13°). The obtained high-flux low-divergence positron beam may have diverse applications in science, medicine, and engineering. [ABSTRACT FROM AUTHOR]

The positive dc corona plasmas between coaxial cylinders in air under the application of a selfsustained criterion with photoionization are investigated in this paper. A photon absorption function suitable for cylindrical electrode, which can characterize the total photons within the ionization region, is proposed on the basis of the classic corona onset criteria. Based on the general fluid model with the self-sustained criterion, the role of photoionization in the ionization region is clarified. It is found that the surface electric field keeps constant under a relatively low corona current, while it is slightly weakened with the increase of the corona current. Similar tendencies can be found under different conductor radii and relative air densities. The small change of the surface electric field will become more significant for the electron density distribution as well as the ionization activity under a high corona current, compared with the results under the assumption of a constant surface field. The assumption that the surface electric field remains constant should be corrected with the increase of the corona current when the energetic electrons with a distance from the conductor surface are concerned. [ABSTRACT FROM AUTHOR]

A novel low specific on-resistance (Ron,sp) lateral double-diffused metal oxide semiconductor (LDMOS) with a buried improved super-junction (BISJ) layer is proposed. A super-junction layer is buried in the drift region and the P pillar is split into two parts with different doping concentrations. Firstly, the buried super-junction layer causes the multiple-direction assisted depletion effect. The drift region doping concentration of the BISJ LDMOS is therefore much higher than that of the conventional LDMOS. Secondly, the buried super-junction layer provides a bulk low on-resistance path. Both of them reduce Ron,sp greatly. Thirdly, the electric field modulation effect of the new electric field peak introduced by the step doped P pillar improves the breakdown voltage (BV). The BISJ LDMOS exhibits a BV of 300 V and Ron,sp of 8.08 mΩ·cm2 which increases BV by 35% and reduces Ron,sp by 60% compared with those of a conventional LDMOS with a drift length of 15 μm, respectively. [ABSTRACT FROM AUTHOR]

In this paper, the specific characteristics of the Trichel pulse generated in wide point-to-plane discharge gaps are investigated and compared with those of the currents generated in narrow gaps. A set of empirical formulas are derived to describe the specific characteristics. The influence of the gap spacing both on the current characteristics and on the coefficients of the formulas is studied. Based on the experiment results, an improvement is made to the space charge calculation method proposed by Lama and Gallo [J. Appl. Phys. 45, 103-113 (1974)] and the calculation results are compared to the ones obtained with Lama and Gallo's original method. With the influence of the space charge considered, the modified method obtains more accurate results of the space charge accumulating in the gap and gives a more precise description of the motion of the space charge in the gap. Based on the calculation results, the influence of the space charge on the distribution of the electric field is examined and the influence of the gap spacing on the current characteristics is also studied. [ABSTRACT FROM AUTHOR]

A novel silicon-on-insulator (SOI) high voltage device with a composite dielectric buried layer (CD SOI) is proposed in this paper. In the proposed structure, the composite dielectric buried layer consists of SI3N4 dielectric and low-A: (relative permittivity) dielectric. The electric field strength in the buried layer is enhanced by the low-k dielectric. The Si3N4 dielectric in the buried layer not only modulates the electric field distribution in the drift region, but also provides a heat conduction path for the SOI layer and alleviates the self-heating effect (SHE). The breakdown voltage (BV) = 362 V for CD SOI is obtained by simulation on a 1 fim SOI layer over 2 jim buried layer, which is enhanced by 26% compared with that of conventional SOI. [ABSTRACT FROM AUTHOR]

A new silicon-on-insulator (SOI) power lateral MOSFET with a dual vertical field plate (VFP) in the oxide trench is proposed. The dual VFP modulates the distribution of the electric field in the drift region, which enhances the internal field of the drift region and increases the drift doping concentration of the drift region, resulting in remarkable improvements in breakdown voltage (BV) and specific on-resistance (Ron,sp). The mechanism of the VFP is analyzed and the characteristics of BV and Ron,sp are discussed. It is shown that the BV of the proposed device increases from 389 V of the conventional device to 589 V, and the Ron,sp decreases from 366 mΩ·cm2 to 110 mΩ·cm2. [ABSTRACT FROM AUTHOR]

A novel silicon-on-insulator (SOI) metal-oxide-semiconductor field effect transistor (MOSFET) with a high figure of merit (FOM) is proposed. The device features a double-sided charge oxide-trench (DCT) and a trench gate extended to the buried oxide. First, the oxide trench causes multiple-dimensional depletion in the drift region, which not only improves the electric field (E-field) strength, but also enhances the reduced surface field effect. Second, self-adaptive charges are collected in the DCT, which enhances the E-field strength of the trench oxide. Third, the oxide trench folds the drift region along the vertical direction, reducing the device cell pitch. Fourth, one side of the DCT regions acts as the body contact of p-well to reduce cell pitch and specific on-resistance (Ron,sp) further. Compared with a trench gate lateral double-diffused MOSFET, the DCT MOSFET increases the breakdown voltage (BV) from 53 V to 158 V at the same cell pitch of 3.5 μm, or reduces the cell pitch by 60% and Ron,sp by 70% at the same BV. The FOM (FOM=BV2/Ron,sp) of the proposed structure is 23 MW/cm2. [ABSTRACT FROM AUTHOR]

A group of complete images on the discharge channel developed in PMMA in quasi-uniform electric field under nanosecond pulses are observed with an on-line transmission microscope. The characteristics of the cumulative breakdown process are also generalized, which include initiating from the vicinity of the cathode, developing to the anode with a branch-like shape, and taking on a wormhole appearance when final breakdown occurs. The concluded characteristics are explained by referring to the conceptions of 'low density domain' and 'free radical' and considering the initial discharge channel as a virtual needle. The characteristics are helpful for designers to enhance the lifetime of insulators employed on a nanosecond time scale. [ABSTRACT FROM AUTHOR]

Self-organization phenomena in ensembles of self-propelled particles open pathways to the synthesis of new dynamic states not accessible by traditional equilibrium processes. The challenge is to develop a set of principles that facilitate the control and manipulation of emergent active states. Here, we report that dielectric rolling colloids energized by a pulsating electric field self-organize into alternating square lattices with a lattice constant controlled by the parameters of the field. We combine experiments and simulations to examine spatiotemporal properties of the emergent collective patterns and investigate the underlying dynamics of the self-organization. We reveal the resistance of the dynamic lattices to compression and expansion stresses leading to a hysteretic behavior of the lattice constant. The general mechanism of pattern synthesis and control in active ensembles via temporal modulation of activity can be applied to other active colloidal systems. [ABSTRACT FROM AUTHOR]

This Letter presents a novel small-sized lateral insulated gate bipolar transistor on silicon-on-insulator substrate (SOI-LIGBT), which features a lowly doped p-type pillar alongside the oxide trench in the drift region. The variation in vertical doping termination technology is also proposed for the first time. The p-pillar layer leads to electric field reshaping in the y-direction, and homogenises current flow lines under the gate and cathode. It results in a very wide forward bias safe operating area (FBSOA) for the proposed SOI-LIGBT, which is obviously improved by over 50% compared with the deep-oxide trench SOI-LIGBT (DT SOI-LIGBT). Moreover, at the same forward voltage drop of 1 V, the turnoff energy loss for the proposed SOI-LIGBT is reduced by 28.5 and 81.2% compared with those of DT SOI-LIGBT and the conventional SOI-LIGBT, respectively. [ABSTRACT FROM AUTHOR]

We present a novel numerical model and simulate preliminarily the charging process of a polymer subjected to electron irradiation of several 10 keV. The model includes the simultaneous processes of electron scattering and ambipolar transport and the influence of a self-consistent electric field on the scattering distribution of electrons. The dynamic spatial distribution of charges is obtained and validated by existing experimental data. Our simulations show that excess negative charges are concentrated near the edge of the electron range. However, the formed region of high charge density may extend to the surface and bottom of a kapton sample, due to the effects of the electric field on electron scattering and charge transport, respectively. Charge trapping is then demonstrated to significantly influence the charge motion. The charge distribution can be extended to the bottom as the trap density decreases. Charge accumulation is therefore balanced by the appearance and increase of leakage current. Accordingly, our model and numerical simulation provide a comprehensive insight into the charging dynamics of a polymer irradiated by electrons in the complex space environment. [ABSTRACT FROM AUTHOR]

This paper presents a new algorithm to simulate the surge corona of power transmission lines in two dimension. The charge simulation method and the finite element method are applied to calculate the electric field, while a time-dependent upwind difference algorithm is applied to calculate the migration of the space charges. The implementation of boundary conditions and the choice of mesh size and time step are discussed to ensure the stability of the proposed algorithm. The Q-V (charge-voltage) curves of impulses applying on single conductor and bundle conductors in a cage having a square cross section are calculated. The simulation results are supported by the published experiments. [ABSTRACT FROM AUTHOR]

Numerical simulations are presented for the ion flow effects on the negative direct current corona in air. One dimensional equivalent steady corona model containing the continuity equations for electrons and ions on the basis of Townsend theory coupled with Poisson’s equation is applied. The conductor radius and the electric field intensity on conductor surface keep constant under the standard atmosphere condition in this paper. The results suggest that the space charges within the plasma region have no influence on the electric field distribution throughout the interelectrode gap, which is only governed by the ion flow. The influences of the gap distance and the corona current on the corona discharge within the plasma region have been investigated. If the voltage-current characteristics of the negative corona discharge are measured, the ion flow region and the plasma region can be investigated individually. Based on Kaptzov’s hypothesis, the plasma region can be investigated solely. [ABSTRACT FROM AUTHOR]

Based on the continuity theorem of electric displacement including interface charges, the enhanced dielectric layer field (ENDIF) for silicon-on-insulator (SOI) high-voltage devices is proposed. The following three approaches for enhancing the dielectric layer electric field E1 to increase the vertical breakdown voltage of a device VB,V are presented: 1) using a thin silicon layer with a high critical electric field ES,C; 2) introducing a low-permittivity dielectric buried layer; and 3) implementing interface charges between the silicon and the dielectric layer. Considering the threshold energy of silicon εT, the formula of ES,C on silicon layer thickness tS is first obtained, which increases sharply with a decrease of tS, and reaches up to 141 V/µm at tS = 0.1 µm. Expressions for E1 and VB,V are given, which agree well with simulative and experimental results. Based on the ENDIF, the new device structures are given, and an E1 value of 300 V/µm has been experimentally obtained for double-sided trench SOI. Moreover, several conventional SOI devices are explained well by ENDIF. [ABSTRACT FROM AUTHOR]

Abstract-A new superjunction LDMOS on silicon-on-insulator (SOl) with a nondepletion compensation layer (NDCL) is proposed. The NDCL can be self-adaptive to provide additional charges for compensating the charge imbalance while eliminating the substrate-assisted depletion effect. In addition, the highdensity oxide interface charges at the top surface of the buried oxide layer (BOX) enhance the electric field in the BOX and improve the vertical breakdown voltage (By). Numerical simulation results indicate that a uniform surface electric field profile is obtained and that the vertical electric field in BOX is increased to 6 x 10[sup6] V/cm, which results in a high BV of 300 V for the proposed device with the BOX thickness of 0.5 μm and drift length of 15 μm on a thin SO! substrate. [ABSTRACT FROM AUTHOR]

A novel silicon-on-insulator (SOI) high-voltage MOSFET structure and its breakdown mechanism are presented in this paper. The structure is characterized by oxide trenches on the top interface of the buried oxide layer on partial SOI (TPSOI). Inversion charges located in the trenches enhance the electric field of the buried layer in the high-voltage blocking state, and a silicon window makes the depletion region spread into the substrate. Both of them modulate the electric field in the drift region; therefore, the breakdown voltage (BV) for a TPSOI LDMOS is greatly enhanced. Moreover, the Si window alleviates the self-heating effect. The influences of the structure parameters on device characteristics are analyzed for the proposed device structure. The TPSOI LDMOS with BV > 1200 V and the buried-layer electric field of EI > 700 V/μm is obtained by the simulation on a 2-μm-thick SOI layer over 2-μm-thick buried oxide layer, and its maximal temperature reduces by 19 and 8.7 K in comparison with the conventional SOI and partial SOI devices. [ABSTRACT FROM AUTHOR]

A super-junction (SJ) SOI-LDMOS with a step doping surface-implanted n-type layer is proposed and optimized which allows high breakdown voltage (BV) and low on-resistance (Ron). The proposed structure overcomes the field effect action in conventional SJ SOI-LDMOS devices, thus achieving the charge compensation between the n and p pillars as well as a near uniform electric field distribution in the drift region in the off-state. The surface-implanted layer also provides a low current path in the on-state. In addition, the analysis result of surface doping distribution is obtained which is a power tool for device designers to provide accurate first-order design schemes. The simulation results show that an increase in the off-state BV by 55% and a reduction of the specific on-resistance by 37.4% are obtained for the proposed device when compared with those of the conventional one. [ABSTRACT FROM AUTHOR]

The electric fields under high-voltage direct current (HVdc) transmission lines and the ions produced by corona affect each other greatly. This paper presents an iterative method to calculate ion flow fields under HVdc bipolar transmission lines in the presence of wind. Both the electric fields and the ion densities are calculated by integral equation method. The method is fast and stable. The results are in good agreement with the experimental data. The ion flow fields under a ± 800-kV bipolar direct current (dc) transmission line are analyzed. [ABSTRACT FROM AUTHOR]

When dc current is injected into the earth through the grounding electrodes of a high-voltage direct current (HVDC) system, transformers in ac system may be under dc bias if the dc currents flowing through the transformers are large enough. In this paper, a numerical method coupling the method of moments (MoM) to circuit equations is presented to calculate the dc current distribution in ac power system caused by an HVDC system. The MoM is used to calculate the electric fields in complex earth structure caused by all the grounding systems including the dc grounding electrodes, the ac substation grounding systems and the long metal pipe lines. The circuit equations are coupled to the moment method to take account of the effects of the transmission lines. By using the method, the dc current distribution in an ac power system caused by an HVDC system is analyzed. Some useful conclusions are drawn from the analyzed results. [ABSTRACT FROM AUTHOR]

An approach coupling indirect boundary element method with charge simulation method to calculate the electric fields around the head of transmission tower and its composite insulators is presented. On the composite insulators, the indirect boundary element method is used, while on the transmission tower and the transmission lines, the charge simulation method is used. Therefore, both the heterogeneous medium such as the composite insulators and the filament metal structure such as the transmission tower and the transmission lines are considered all together. The electric field distribution around a 330-kV transmission tower and its composite insulators was analyzed. The method gives the possibility to model very complex geometries. [ABSTRACT FROM AUTHOR]

In this paper, the electric-field distribution around the composite insulators and the heads of transmission towers is calculated by a model coupling the indirect boundary-element method to the moment method. The heterogeneous media, such as the composite insulators and the filament metal structures such as the transmission towers and the transmission lines, are considered altogether. The method can take into account not only the permittivity but also the resistivity of the media by using the complex resistivity in the frequency domain. The electric-field distribution around a three-phase 330-kV transmission tower with composite insulators was analyzed. The electric fields on the surfaces of the grading rings and the phase subconductors and at the ends of the composite insulators are analyzed. Both the method and the results are useful for the design of high-voltage transmission lines. [ABSTRACT FROM AUTHOR]

The design of grounding system often relies on the performance simulations. The evaluation of the current distribution of grounding system for many frequencies by using the method of moments (MoM) may take a long time since the impedance matrix must be recomputed at each new frequency. A multiobject adaptive spatial sampling approach is presented to construct the fitted model of the electric field intensity generated by a horizontal electric dipole. The [Z] matrix spatial interpolation technology with MoM is described to reduce the computational time needed for the transient characteristics analysis of a horizontal grounding system. The accuracy and computational time of the [Z] matrix interpolation method are compared with those of the direct MoM. The numerical examples show that the [Z] matrix spatial interpolation method can reduce the computation requirement effectively. [ABSTRACT FROM AUTHOR]

The article informs that the an electro-chemical reaction is made up of a series of chemical and physical steps occurring at very small length scales. The transfer of an electron between the electrode surface and a redox molecule takes place over a distance no greater that 2 nm and occurs in an interfacial region defined by the radius of adsorbed ions and solvent molecules, as welt as the distance that surface electric fields extend into the solution. In the late 1970s, analytical chemists first considered the role of electrode size in relation to electrochemical length scales. Electrodes of nanometer dimensions are also employed in in-situ electrochemical scanned probe microscopies, although their electrochemical behavior is not always of primary interest in these applications.

The electromagnetic environments (EMEs) of the planned Zhongguancun Software Park near transmission lines, including electrical field, magnetic field, and ground potential rise under three cases of lightning stroke, normal operation, and short-circuit faults, are assessed by numerical analysis. The power frequency EMEs of the software park are below the maximum ecological allowed exposure values for the general public; , nevertheless, the power frequency magnetic field may interfere with the sensitive computer display unit. The influence of short-circuit fault in two different cases of remote short circuit and neighboring short circuit on the software park is discussed. The main problem we must pay attention to is the ground potential rise in the software park due to neighboring short-circuit fault; it would threaten the safe operation of electronic devices in the software park. On the other hand, the lightning stroke is a serious threat to the software park. How to improve the EMEs of the software park is discussed. [ABSTRACT FROM AUTHOR]

We report amplified spontaneous emission (ASE) in an optically pumped symmetric thin film waveguide based on poly [2-methoxy-5-(2′-ethylhexyloxy)-1, 4-phenylene vinylene] (MEH-PPV) and electric-field modulation of the ASE in the MEH-PPV thin film. The electric-field quenching of the ASE at 620 nm and the spontaneous emission (SE) at 580 nm was observed, which increased with the electric field. The ASE intensity was more effectively quenched than the SE intensity as the field increased. The field dependence of the ASE and the SE intensity can be attributed to field-induced dissociation of photogenerated excitons in the MEH-PPV thin film. [ABSTRACT FROM AUTHOR]

A new lateral power MOSFET structure [folded-accumulation LDMOS (FALDMOS)] is proposed, in which the silicon-substrate surface is trenched to form a folded shape from the channel to the drain electrode and the gate is extended to the drain. The majority-carrier accumulation layer is formed as the device is in ON state due to the extended gate in the drift region whose concentration is higher than that in a conventional LDMOS at the same breakdown voltage (By), resulting from the additional electric-field modulation, and an extra majority carrier is introduced on the sidewall of the trench, which reduced the on-resistance of the drift region further. In addition, the channel density is doubled because of trenching the folded channel, which reduced the channel on-resistance. It indicates by simulation that the specific on-resistance of 4.6Ω · mm2 with a BV of 27.4 V in FALDMOS is lower than that of the previously reported lowest one. [ABSTRACT FROM AUTHOR]

Breakdown mechanism for a high-voltage n-channel LDMOS compatible with a high-voltage integrated circuit (HVIC) on a p-type silicon-on-insulator (SOI) layer is investigated theoretically and experimentally. The device is characterized by buried n-islands on a buried oxide layer (BOX). For the proposed structure, ionized donors in n-islands enhance the bottom-interface electric field of the SOI layer from 10 V/μm in the conventional devices on p-SOI layer to 27 V/μm, resulting in enhancement of the BOX electric field EI from 30 to 82 V/μm. Moreover, holes located between the depleted n-islands help to increase EI as well. Both improve the blocking capability of the device. A 660-V SOI LDMOS is obtained, in which the implanted n-type drift region, along with the n-islands on a p-type SOI layer, realizes the self-isolation in HVIC. [ABSTRACT FROM AUTHOR]

A novel silicon-on-insulator (SOl) high-voltage de- vice with a compound buried layer (CBL SOl) consisting of two oxide layers and a polysilicon layer between them is proposed. Its breakdown characteristic is investigated theoretically and experimentally. Theoretically, its vertical breakdown voltage (BV) is shared by two oxide layers; furthermore, the electric field in the lower buried oxide layer of E12 is increased from about 78 to 454 V/jtm by holes collected on the bottom interface of the polysilicon. Both result in an enhanced BY. Experimentally, 762-V SO! diode is obtained. The maximal temperature of CBL SO! diode is reduced by 16.9 K because a window in the upper buried oxide layer alleviates the self-heating effect. [ABSTRACT FROM AUTHOR]

A novel 2-μm thin-drift-layer power MOSFET with an n-type floating buried layer (FBL) in substrate is proposed in this letter. Since the charges in the buried layer modulate the bulk electric field, a nearly uniform electric field is obtained, and the vertical breakdown voltage (BV) is significantly improved. Simulation results show that the BV of the proposed FBL lateral double-diffused MOSFET (LDMOSFET) is increased from 743 V of the conventional LDMOSFET to 1332 V with the same 100 μm drift region length. Furthermore, the figure-of-merit of the FBL-LDMOSFET is better than that of the conventional LDMOSFET. [ABSTRACT FROM AUTHOR]

A novel silicon-on-insulator (SOI) high-voltage device structure with double-sided trenches on the buried oxide layer (DT SOl) is proposed and its breakdown characteristics are investigated theoretically and experimentally in this letter. Theoretically, the charges implemented in the DTs, whose density changes with the drain voltage, increase the electric field in the buried layer and modulate the electric field in the drift region, which results in the enhancement of the breakdown voltage (BV). Experimentally, the BV of 730 V is obtained for the first time in SOI LDMOS with DT on 20-µm SOI layer and 1-µm buried oxide layer. [ABSTRACT FROM AUTHOR]

By using three-dimensional particle-in-cell simulations, we investigate the dynamics of ultraintense Laguerre–Gaussian (LG) laser pulses interacting with a wire target. When a relativistic LG-mode laser pulse sweeps a wire target, annular electron bunches with attosecond duration are periodically dragged out of the left tip of the wire. Due to the radial laser electric field force exerted on the electrons, the annular bunches are tightly constrained near the target surface and steadily propagate along the wire. A strong return current is thus induced to satisfy the plasma neutralization condition. Once leaving from the right tip of the target, the electron emission angle gradually decreases and each hollow electron bunch is converged into an electron disc. Under the action of the longitudinal electric field, electrons are continuously accelerated to 100s MeV. At the same time, the laser angular momentum is transferred efficiently to the beam angular momentum (BAM) of the bunches. The structure of the dense short electron bunches is stable and keeps intact for more than 300 fs. We can manipulate the quality of the bunches by changing the laser and target parameters, such as the laser handedness and intensity, beam waist radius, wire length and radius. The scheme paves the way for the generation of high-quality attosecond electron bunches with low divergence, high beam charge and large BAM, which will have wide-range applications in various domains. [ABSTRACT FROM AUTHOR]

An analytical model for a novel triple reduced surface field (RESURF) silicon-on-insulator (SOI) lateral double-diffused metal–oxide–semiconductor (LDMOS) field effect transistor with n-type top (N-top) layer, which can obtain a low on-state resistance, is proposed in this paper. The analytical model for surface potential and electric field distributions of the novel triple RESURF SOI LDMOS is presented by solving the two-dimensional (2D) Poisson’s equation, which can also be applied to single, double and conventional triple RESURF SOI structures. The breakdown voltage (BV) is formulized to quantify the breakdown characteristic. Besides, the optimal integrated charge of N-top layer (Qntop) is derived, which can give guidance for doping the N-top layer. All the analytical results are well verified by numerical simulation results, showing the validity of the presented model. Hence, the proposed model can be a good tool for the device designers to provide accurate first-order design schemes and physical insights into the high voltage triple RESURF SOI device with N-top layer. [ABSTRACT FROM AUTHOR]

A low specific on-resistance SOI LDMOS with a novel junction field plate (JFP) is proposed and investigated theoretically. The most significant feature of the JFP LDMOS is a PP—N junction field plate instead of a metal field plate. The unique structure not only yields charge compensation between the JFP and the drift region, but also modulates the surface electric field. In addition, a trench gate extends to the buried oxide layer (BOX) and thus widens the vertical conduction area. As a result, the breakdown voltage (BV) is improved and the specific on-resistance (Ron,sp) is decreased significantly. It is demonstrated that the BV of 306 V and the Ron,sp of 7.43 mΩ·cm2 are obtained for the JFP LDMOS. Compared with those of the conventional LDMOS with the same dimensional parameters, the BV is improved by 34.8%, and the Ron,sp is decreased by 56.6% simultaneously. The proposed JFP LDMOS exhibits significant superiority in terms of the trade-off between BV and Ron,sp. The novel JFP technique offers an alternative technique to achieve high blocking voltage and large current capacity for power devices. [ABSTRACT FROM AUTHOR]

This paper describes the successful fabrication of 4H-SiC junction barrier Schottky (JBS) rectifiers with a linearly graded field limiting ring (LG-FLR). Linearly variable ring spacings for the FLR termination are applied to improve the blocking voltage by reducing the peak surface electric field at the edge termination region, which acts like a variable lateral doping profile resulting in a gradual field distribution. The experimental results demonstrate a breakdown voltage of 5 kV at the reverse leakage current density of 2 mA/cm2 (about 80% of the theoretical value). Detailed numerical simulations show that the proposed termination structure provides a uniform electric field profile compared to the conventional FLR termination, which is responsible for 45% improvement in the reverse blocking voltage despite a 3.7% longer total termination length. [ABSTRACT FROM AUTHOR]

This paper is concerned with the inverse problem of scattering of time-harmonic electromagnetic waves by an impenetrable obstacle buried in the lower half-space of a two-layered background medium. We prove that the buried obstacle and its physical property can be uniquely determined from a knowledge of the tangential component of the electric field on some two-dimensional device in the upper half-space corresponding to all incident electric dipoles located on another two-dimensional device in the upper half-space with two different polarizations. The key ingredient of our proof is a novel reciprocity relation established in this paper for the solution of the scattering problem of the electric dipole located at two different source points. [ABSTRACT FROM AUTHOR]