A new 4H-SiC lateral merged double Schottky (LMDS) rectifier withexcellent forward and reverse characteristics

The novel characteristics of a new Schottky rectifier structure, known as the lateral merged double Schottky (LMDS) rectifier, on 4H-SiC are explored theoretically and compared with those of the compatible conventional 4H-SiC Schottky rectifiers. The anode of the proposed lateral device utilizes the trenches filled with a high barrier Schottky (HBS) metal to pinch off a low barrier Schottky (LBS) contact during reverse bids. Numerical simulation of any such SiC structure is complicated by the fact that the thermionic emission theory predicts the reverse leakage current to be orders of magnitude smaller than the measured data. We, therefore, first propose a simple empirical model for barrier height lowering to accurately estimate the reverse leakage current in a SiC Schottky contact. The accuracy of the empirical model is verified by comparing the simulated reverse leakage current with the reported experimental results on different SiC Schottky structures. Using the proposed empirical model, the two-dimensional (2-D) numerical simulations reveal that the new LMDS rectifier demonstrates about three orders of magnitude reduction in the reverse leakage current and two times higher reverse breakdown voltage when compared to the conventional lateral low barrier Schottky (LLBS) rectifier while keeping the forward voltage drop comparable to that of the conventional LLBS rectifier     

一种具有高正向阻断电压及优良开关特性的新型静电感应晶闸管

设计并构造了一种具有条状阳极P-缓冲层结构（SAP-B）的新型静电感应晶闸管。该结构以具有p- 缓冲层和嵌入p+发射区（条状阳极区）的弱掺杂n-发射区（泄漏阳极区）为特点。与传统扩散源区埋栅结构相比,SAP-B结构可进一步简化工艺,并将扩散源区埋栅结构静电感应晶闸管的正向阻断电压从1000V提高至1600V,阻断增益从40提高至70,同时将关断时间从0.8μs降低至0.4μs。     

A new static induction thyristor with high forward blocking voltage and excellent switching performances

A new static induction thyristor (SITH) with a strip anode region and p~- buffer layer structure (SAP-B) has been successfully designed and fabricated. This structure is composed of a p~- buffer layer and lightly doped n~-regions embedded in the p~+-emitter. Compared with the conventional structure of a buried-gate with a diffused source region (DSR buried-gate), besides the simple fabrication process, the forward blocking voltage of this SITH has been increased to 1600 V from the previous value of 1000 V, the blocking gain increased from 40 to 70, and the turn-off time decreased from 0.8 to 0.4μs.     

倍流整流器电路拓扑研究

介绍了一种新型的整流器电路,并提出了几种变换拓扑结构以及这种整流器的优缺点。最后通过PSPICE仿真软件进行了仿真验证。     

Diode characteristics and edge effects of metal-semiconductor diodes

When investigating metal-semiconductor barriers, measured I–V-characteristics are often used for deducing barrier height, origin of current components etc. This paper discusses under what conditions errors may be caused by edge-generated currents, and the influence of guard rings is investigated. The system studied was gold on chemically prepared silicon. Investigating reverse characteristics, it was shown that, for diodes having diameters of a few mm, edge effects are important when the silicon resistivity is $\text{? 100 Ω}\text{cm}$, but negligible for lower ?. Diodes with no guard rings (NGR) had currents several times those surrounded by rings held at the same voltage (balanced guard ring, BGR), at low voltages, and the excess increased with voltage. Studies of activation curves for the current revealed that the current in the BGR case essentially obeyed a Schottky barrier expression (barrier height 0·75–0·80 V) while NGR curves showed appreciably smaller activation energies, indicating contribution of surface- and volume-generated currents at the edge. For diodes of low resistivity avalanche effects are important at high voltages. The main features of the current variation with voltage for higher resistivity BGR diodes (up to $\text{30}\text{k}\text{Ω}\text{cm}$) are in agreement with the image-force lowering effect and the influence of bulk generation current.     

A simple power diode model with forward and reverse recovery

The basic diode charge-control model used in SPICE is extended by employing the lumped charge concept of J.G. Linvill and J.F. Gibbons (1961) to derive a set of model equations from simplified device physics. Both forward and reverse recovery phenomena are included as well as emitter recombination. The complete model requires only seven relatively simple equations and three additional device parameters beyond the genetic SPICE diode model. A major feature of the model is that the same equations are valid through all regions of operation     

An integrated 500-V power DMOSFET/antiparallel rectifier devicewith improved diode reverse recovery characteristics

We propose and demonstrate an integrated power MOSFET structure where a fast-switching antiparallel rectifier with improved reverse recovery is integrated within the conventional DMOSFET structure. In this device, the source metal electrode of the DMOSFET is extended to the n-drift region, and a thin p-layer is implanted under the metal forming a junction diode antiparallel to the DMOSFET. Analysis of the experimental switching performance of the integral diode in 500-V integrated power DMOSFET/antiparallel rectifier devices indicates at least 30% decrease in peak reverse current and minority carrier stored charge at 100°C     

A high-quality rectifier based on the forward topology with secondary-side resonant reset

The use of buck-derived topologies for unity power factor AC-to-DC applications is limited by their inherent inability to draw current from the line in those intervals, during the line half period, in which the input voltage is lower than the output one. This drawback is overcome in the proposed high-quality rectifier based on the forward topology with secondary-side resonant reset. The employed secondary side reset capacitor is able to provide proper transformer reset by recycling the transformer stored energy to the load and, at the same time, it allows to draw energy from the line even when the input voltage is lower than the output one. Consequently, besides a better utilization of the transformer core (bipolar core excitation), a low distorted input current waveform can be obtained with a power factor close to unity. Experimental results of a 200 W prototype confirm the theoretical expectations.     

一种新型肖特基整流管设计

在研究功率肖特基整流管的基础上,针对反向击穿电压、漏电流、抗浪涌能力的提高,采取加场限环的方法,设计并制造了一种新型结势垒肖特基整流管(Junction barrier Schottky rectifier,JBS)。通过从有源区参数、外延材料、流片工艺、产品电参数、可靠性等方面进行了全面设计。经测试,电参数水平正向电压VF：0.85-0.856V,反向电流IR：4-50.5uA,反向电压VR:307.5-465.2V,抗静电水平从低温退火的6-12KV提高到15KV,经高温直流老化后,可靠性电参数水平满足预期的设计要求。     

Interlocked MXene/rGO aerogel with excellent mechanical stability for a health-monitoring device

Two-dimensional (2D) materials have attracted considerable interest thanks to their unique electronic/physical–chemical characteristics and their potential for use in a large variety of sensing applications. However, few-layered nanosheets tend to agglomerate owing to van der Waals forces, which obstruct internal nanoscale transport channels, resulting in low electrochemical activity and restricting their use for sensing purposes. Here, a hybrid MXene/rGO aerogel with a three-dimensional (3D) interlocked network was fabricated via a freeze-drying method. The porous MXene/rGO aerogel has a lightweight and hierarchical porous architecture, which can be compressed and expanded several times without breaking. Additionally, a flexible pressure sensor that uses the aerogel as the sensitive layer has a wide response range of approximately 0–40 kPa and a considerable response within this range, averaging approximately 61.49 kPa^–1. The excellent sensing performance endows it with a broad range of applications, including human-computer interfaces and human health monitoring.     

Peristaltic charge-coupled device: a new type of charge-transfer device

A new type of charge-transfer device (c.t.d.) is presented. The main difference from known c.t.d.s is that the bulk transport of majority carriers is used; this, together with a capacitive decoupling of the carriers from the electrode, yields a high transfer efficiency, possibly even up to the gigahertz range. Experiments agree with expectations.     

Analysis, design, and implementation of an active clamp forward converter with synchronous rectifier

The system analysis, circuit design, and implementation of active clamp based forward converter with synchronous rectifier are presented in this paper. To release the energy stored in the leakage inductor and to minimize the spike voltage at the transformer primary side, active clamp circuit included one clamp switch and one clamp capacitor is adopted in the circuit. Based on the partial resonance with the output capacitor of switch and the leakage inductor of transformer, the main switch is turned on at zero voltage switching (ZVS). The clamp switch is also operated at ZVS operation based on the resonance of leakage inductor and clamp capacitor. The synchronous switches are used at the secondary side to further reduce the conduction losses. The experimental results based on the laboratory prototypes are presented to verify the circuit performance.     

A novel P-channel nitride-trapping nonvolatile memory device with excellent reliability properties

A novel P-channel nitride trapping nonvolatile memory device is studied. The device uses a P/sup +/-poly gate to reduce gate injection during channel erase, and a relatively thick tunnel oxide (>5 nm) to prevent charge loss. The programming is carried out by low-power band-to-band tunneling induced hot-electron (BTBTHE) injection. For the erase, self-convergent channel erase is used to expel the electrons out of nitride. Experimental results show that this p-channel device is immune to read disturb due to the large potential barrier for hole tunneling. Excellent P/E cycling endurance and retention properties are demonstrated. This p-channel device shows potential for high-density NAND-type array application with high-programming throughput (>10 Mb/sec).     

A new space-vector-modulated control for a unidirectionalthree-phase switch-mode rectifier

A unidirectional three-phase switch-mode rectifier that delivers sinusoidal input currents in phase with the corresponding input phase voltages is proposed and analyzed in this paper. In the proposed topology, three AC switches are placed before the bridge rectifier and, respectively, across two power lines. A simple control scheme combing space-vector modulation and hysteresis current control is presented. Sinusoidal input line currents are observed in experimental results     

The three-terminal fuse: a new switching device

A new switching device has been conceived and reduced to practice. This device is a once-programmable three-terminal fuse (TTF) with an on-resistance of a good metallic conductor typically employed in integrated circuits, and an off-resistance which is essentially infinite, as between two such disconnected conductors. In the new structure the fusible circuit path is fully isolated from the control electrode both before and after programming. The ideal switching characteristics of this device make it useful in a variety of analog and digital applications, particularly where field programmability, precision trimming, or redundancy/repair are required. We discuss the basic concept of the TTF and briefly highlight some of its possible applications     

Novel quantum-well optical bistability device with excellent on/offratio and high speed capability

A novel optical bistability device is proposed and analysed in which the Stark effect of a multiple quantum well is used in combination with a negative resistance device. The device is found to possess an excellent on/off ratio (19:1) and high speed capability (τ<10 ps), while the required optical power P is as small as 1 mW or less with a bias voltage of 5V, giving a Pτ product of 1~10 fJ     

A new ZVS-PWM unity power factor rectifier with reduced conductionlosses

This paper introduces a new single-phase high power factor rectifier, which features regulation by conventional PWM, soft commutation and instantaneous average line current control. Furthermore, thanks to the use of a single converter, instead of the conventional configuration composed of a four-diode front-end rectifier followed by a boost converter, a significant reduction in the conduction losses is achieved. A prototype rated at 1.6 kW, operating at 70 kHz, with an input AC voltage of 220 Vrms and an output voltage of 400 V_DC has been implemented in the laboratory. An efficiency of 97.8 % at 1.6 kW has been measured. Analysis, design, and the control circuitry are also presented in the paper     

Second breakdown in the forward and reverse base current region

At a constant forward or reverse base current, the pulse length of a collector current pulse, which forces a transistor under test into second breakdown, is measured. For all transistors measured, the pulse lengthlog Delta tis plotted vs. the collector pulse height, with the forward or reverse base current as a parameter. According to our observations, one can distinguish three types of transistors, as far as their secondary breakdown characteristics are concerned. 1) Good epitaxial transistors show an approximately linear dependence oflog Delta tto Icwith a negative slope. The curves for reverse base current are displaced parallel to the ones for forward base current, the energy of the pulses not being much different in both cases. 2) Bad epitaxial transistors show an S-shaped curve oflog Delta tvs. Icfor reverse base currents. A deep minimum in second breakdown energy is observed at low collector currents. These transistors will readily fail in practical circuits, where the base current is allowed to reverse. 3) With homogeneous material, thelog Delta tvs. Iccurves for forward and reverse base currents practically coincide. This method has revealed that a large number of transistor types, including overlay structures, show a decrease of energy handling capability of two to three orders of magnitude at collector currents of about 100 mA when the base current is reversed. It has also proved to be an indispensable tool in the development of high-frequency high power devices, which combine good electrical and second breakdown properties.     

Diode forward and reverse recovery model for power electronic SPICEsimulations

A pn-diode micro-model representing forward and reverse recovery phenomena for power electronic simulation, especially simulations using SPICE2 is presented. The model is proposed to compensate the incompleteness of the diode model in current circuit simulation packages. In the forward recovery submodel, the diode bulk resistance modulation and its forward current dependence are included. In the reverse recovery submodel, the charge control equation for excess storage carriers is employed to simulate the detailed behavior. A procedure is described for extracting the model's physical parameters from data sheet information. The model is verified by a comparison of experimental results for several different tests with SPICE simulations. A discussion is given of extending the applicability of the micro-model to the simulation of p-i-n diode behaviour     

Three-level oscillator: a new form of transferred-electron device

Electron transfer between three appropriately coupled sets of conduction-band valleys produces transport properties peculiarly favourable for transferred-electron devices. The necessary conditions should obtain in InP and in InP-InAs and InSb-GaSb alloys. Monte Carlo calculations of the velocity/field characteristics for these materials are described.