Very High Speed Static Induction Thyristor

The super junction (SJ) drift is used in internal transparent collector IGBT.The influences of position of local carrier lifetime region, local carrier lifetime, and buffer layer doping level on the devices' trade-off characteristics have been simulation studied.The results show that for given local carrier liftetime, the turn-off losses may have a valley value E offmin .The higher local carrier lifetime is, the higher E offmin will be.Several factors are at work.Competition effects for excess carrier extraction through reverse biased super junction and forward biased collector may be one reason.Infinite excess carrier recombination velocity in local carrier lifetime control region leads to the back-emitter injection efficiency γ e be no less than certain value.In addition; increasing buffer layer doping level appropriately could win better trade-off and wider trade-off range.

This thesis examines the Class D tuned amplifier, emphasizing the factors which govern its use as a Class D power oscillator. The relative merits of the voltage-switched and current-switched modes for use in an oscillator are discussed. The most desirable properties are exhibited by the current-switched mode, therefore the current-switched amplifier is examined as a basis for the oscillator circuit. A comparison of sinusoidal drive and quasi-voltage drive for the current-switched amplifier illustrates the improved collector current rise time capability of the quasi-voltage drive. Factors such as saturation voltage, base storage time, current rise time, and passive collector circuit components are investigated to determine their effect on the overall efficiency of the quasi-voltage driven amplifier. It is shown the effect of long storage time may be neutralized by delay time and that rise and fall times are short and relatively unimportant. Saturation voltage and tuned circuit losses are shown to present the major efficiency limitation both at higher powers and higher frequencies. It is demonstrated that the phase lag caused by storage time and rise time must be compensated if the Class D oscillator is to be efficient.

We report results of both theoretical and experimental studies of optical precursorsgenerated from a square-modulated probe laser pulse having a finite rise and fall time andpropagating through a cold atomic ensemble, under the conditions of either atwo-level Lorentz absorber system or a three-level system with electromagneticallyinduced transparency (EIT). Because of the finiteness of the rise (and fall) time,the precursor signal is observed to decrease with increasing optical depth (α0L). We find that the precursor can experience little absorption even at high opticaldepth if the rise (and fall) time is sufficiently short. At an optical depth ofα0L = 42, the normalized precursor peak intensity is observed to increase from 9% to 27% when therise (and fall) time is shortened from 7 to 3 ns. Meanwhile, we reaffirm that there is noviolation of Einstein’s causality principle in light propagation through both slow and fastlight media. In the EIT system with high optical depth, the main field propagates with asubluminal group velocity and it is separated from the precursor. In the two-level system,the effect of negative group velocity in the anomalous dispersion regime is observed, but wedetect no advancement in the rising edge of the precursors. In both cases, theleading edges of the precursors show no detectable delay to that through vacuum.

A new thyristor structure-a class of the double-gate (DG) static-induction (SI) thyristors-was fabricated and showed quick dual-gate current controllability and less turn-off tailing current, because the anode current can be controlled by both the first and the second gate and the electrons stored at the second gate can be discharged through the second gate circuit in a very short time at the turn-off process. Moreover, the DG SI thyristors have a capability of lower forward voltage drop and faster switching speed than those values of the single-gate SI thyristor.

The performances of various 1200 V insulated gate bipolar transistor (IGBT) structures for hard- and soft-switching (both the zero-voltage and the zero-current switching) at high temperature and under various test conditions are investigated in detail. A comparison is made between a conventional planar punchthrough IGBT (P-IGBT) using global lifetime control, a trench punchthrough IGBT (T-IGBT) using local lifetime control and a enhanced planar punchthrough IGBT (N-IGBT) also using the local lifetime control process. A simple and effective specific test circuit allows hard- and soft-switching operating modes, and provides also an independent control on the test parameters (load current, clamping voltage, gate resistance, temperature, dead times). It is highlighted that the local lifetime control is very efficient at high temperature reducing especially the turn-off losses. Furthermore, the T-IGBT exhibits very good performances during hard- and soft-switching turn-off, but this is not the case during hard-switching and zero-voltage switching turn-on. Due to its high input capacitance, the hard-switching turn-on losses are relatively high. Regarding the N-IGBT, it presents good performances under hard-switching and also zero-voltage switching. However, like the T-IGBT, its structure has a strong inductance behavior during zero-voltage turn-on increasing the conductivity modulation lag and also the voltage spike leading to high losses. All these data allow to provide useful information for the devices modeling, design, and optimization.

This paper presents an ultra small reverse recovery charge Qrr diode (USQ-Diode) for Insulated Gate Bipolar Transistor (IGBT) modules. The USQ-Diode has a thin p-layer anode with low impurity concentrations, p+ stripe anodes, and lifetime control by He ion irradiation. By employing the thin p-layer anode, the injection of holes into the n-layer as minority carriers was significantly reduced near the pn junction. By using the He ion irradiation, crystal defects for lifetime control were localized near the pn junction. With the combined effects from both the reduced injection of holes and the local lifetime control by the He ion irradiation, as compared to the conventional pn diode, the USQ-Diode realized such superior characteristics as 1/5 times smaller reverse recovery charge and 0.2 V lower forward voltage drop.

Energy and dose mixing concept, applied in ion irradiation technology for local lifetime tailoring, is shown to be capable of creating a customer-specific lifetime profile. The electrical parameters of power diode, subjected to the new ion irradiation concept, are compared with those ones resulting from the energy dispersed alpha particle irradiation.

This paper presents 2-D numerical simulation results of single-event burnout (SEB) in power planar vertical double-diffused MOSFET (VDMOSFET) with localized carrier lifetime control. A low carrier lifetime control region (LCLCR) is introduced to accelerate the recombination rate of the generated holes caused by an ion's impact. The optimal localized range with LCLCR in epitaxial layer has been investigated. The SEB inhibition mechanism with LCLCR is analyzed and discussed. A VDMOSFET with localized LCLCR can operate like a normal VDMOSFET and can have improved SEB performance effectively. In addition, the leakage current density in breakdown characteristics of VDMOSFET is studied based on the variation of carrier lifetime.

To suppress the reverse recovery surge voltage of silicon power diodes, the effects of adjusting trap energy levels through local lifetime control were investigated by device simulation and theoretical analysis of the Shockley–Read–Hall (SRH) model. In general, local lifetime control techniques localize carrier traps at the anode side of a diode and optimize the carrier lifetime profile to suppress surge voltage. However, the suppression effect of a certain localized trap density distribution on surge voltage varies with a change in trap energy level, even if the trap density distribution is the same. It became clear that deep trap energy levels suppress surge voltage more than shallow trap energy levels at 1000 A/cm2 or less. Thus, deep trap energy levels such as Et − Ei = 0.0–0.2 eV are favorable for suppressing surge voltage in almost all power devices.

Ternary alloy CdS<sub><i>x</i></sub>Se<sub>1–<i>x</i></sub> has the physical properties of CdS and CdSe, and its band gap can be adjusted by changing the component ratio of the elements. The alloy has excellent photoelectric properties and has potential application in optoelectronic devices. Although one has made some research progress of the CdSSe-based photodetectors, their performances are still far from the commercial requirements, so how to improve the performance of the device is the focus of current research. In this work, a single crystal CdS<sub>0.42</sub>Se<sub>0.58</sub> nanobelt device is first prepared by thermal evaporation. Under 550 nm illumination and 1 V bias, the ratio of photocurrent to dark current of the device is 1.24×10<sup>3</sup>, the responsivity arrives at 60.1 A/W, and the external quantum efficiency reaches 1.36×10<sup>4</sup>%, and the detectivity is 2.16×10<sup>11</sup> Jones. Its rise time and fall time are about 41.1/41.5 ms, respectively. Secondly, after the CdSSe nanobelt is decorated by Au nanoislands, the optoelectronic performance of the device is significantly improved. Under 550 nm illumination and 1 V bias, the <i>I</i><sub>p</sub>/<i>I</i><sub>d</sub> ratio, responsivity, external quantum efficiency and detectivity of the device are increased by 5.4, 11.8, 11.8 and 10.6 times, respectively, and the rise time and fall time are both reduced to half of counterparts of single CdSSe nanobelt. Finally, the microscopic physical mechanism of the enhanced optoelectronic performance of the device is explained based on localized surface plasmon resonance of Au nanoislands. After the combination of gold nanoislands and CdSSe nanobelt, the difference in Fermi level between them results in the transfer of electrons from CdSSe nanobelt to Au nanoislands, thus forming an internal electric field at the interface, which is directed from CdSSe nanobelt to Au nanoislands. Under illumination, the electrons in the Au nanoislands acquire enough energy to jump over the Schottky barrier because of localized surface plasmon resonance. These photoexcited hot electrons are trapped and stored in extra energy levels above the conduction band minimum, and then are cooled down to the band edge, thus realizing the transfer of electrons from Au nanoislands to CdSSe nanobelt. Moreover, the internal electric field also greatly promotes the transfer of hot electrons from Au nanoislands to CdSSe nanobelt, and inhibits the recombination of carriers at the interface, resulting in large photocurrent. Our work provides an effective strategy for fabricating high-performance photodetectors without increasing the device area.

In this paper, the surface discharge current pulses of PEEK (polyether-ether-ketone) under positive repetitive square voltage are measured. The effects of voltage rise time and fall time on pulse parameters of discharge current, instantaneous voltage of discharge and time-lag of discharge are analyzed in detail. The results show that the amplitude of discharge current and the instantaneous voltage of discharge decrease, and the time-lag of discharge and the dispersion of time-lag increase with the increase of voltage rise time. With the increase of voltage fall time, the amplitude of discharge current decreases and the instantaneous voltage of discharge, the time-lag of discharge and the dispersion of time-lag increase. To analyze the influence mechanism of voltage rise time and fall time on surface discharge, the accumulation of surface charge under repetitive square voltage is regarded as a periodic process. Besides, the correlation between forward discharge and back discharge in the process of discharge is analyzed, and the development of discharge is analyzed by using the time-lag theory. Furthermore, the relationship between instantaneous discharge voltage and voltage slew rate is revealed, and the surface charge accumulation processes under different voltage rise times and fall times are compared to reveal the influence mechanism of rise time and fall time on the surface discharge under positive repetitive square voltage.

In order to reduce power losses and Junction-to-case temperature (ΔT(j-c)) of RC-IGBTs, optimization of both carrier distribution in drift-layer and the diode layout is required. In this study, we propose 3^rd generation 650V RC-IGBT based on CSTBT™, which achieves a significant reduction of AT(j-c) using Local Lifetime Control (LLC) with proton implantation and high density arranged diode layout. Our proposed 3rd generation RC-IGBT successfully reduces power losses by 5% and AT(j-c) by 18%.

A comprehensive temporal analysis has been performed on the 319 brightest GRBs with T90 > 2s from the BATSE current catalog. The GRBs were denoised using wavelets and subjected to an automatic pulse selection algorithm as an objective way of identifying pulses and quantifying the eects of neighbouring pulses. The number of statistically signicant pulses selected from the sample was greater than 3000. The rise times, fall times, full-widths at half-maximum (FWHM), pulse amplitudes and pulse areas were measured and the frequency distributions are presented here. All are consistent with lognormal distributions provided the pulses are well separated. The distribution of time intervals between pulses is not random but compatible with a lognormal distribution when allowance was made for the 64 ms time resolution and a small excess (5%) of long duration intervals that is often referred to as a Pareto-L evy tail. The time intervals between pulses are most important because they may be an almost direct measure of the activity in the central engine. Lognormal distributions of time intervals also occur in pulsars and SGR sources and therefore provide indirect evidence that the time intervals between pulses in GRBs are also generated by rotation powered systems with super-strong magnetic elds. A range of correlations are presented on pulse and burst properties. The rise and fall times, FWHM and area of the pulses are highly correlated with each other. The pulse amplitudes are anticorrelated with the FWHM. The time intervals between pulses and pulse amplitudes of neighbouring pulses are correlated with each other. It was also found that the number of pulses, N, in GRBs is strongly correlated with the fluence and duration and that can explain the well known correlation between duration and fluence. The GRBs were sorted into three categories based on N i.e. 3 N 12, 13 N 24 and N 25. The properties of pulses before and after the strongest pulse were compared for three categories of bursts. No major dierences were found between the distributions of the pulse properties before and after the strongest pulse in the GRB. However there is a strong trend for pulses to have slower rise times and faster fall times in the rst half of the burst and this pattern is strongest for category 3 N 12. This analysis revealed that the GRBs with large numbers of pulses have narrower and faster pulses and also larger fluences, longer durations and higher hardness ratios than the GRBs with smaller numbers of pulses. These results may be explained by either homogeneous or inhomogeneous jet models of GRBs. The GRBs with larger number of pulses are closer to the axis if varies with the opening angle of the jet and the imprint of the jet is preserved in the pulse structure of the burst. The distribution of the number of pulses per GRB broadly reflects the beaming by the jet.

Temperature is an important factor affecting the dynamic processes of corona discharge, since the ionization, attachment, and mobility of charged particles are directly related to temperature. Most existing research has investigated the temperature effect on corona discharge through experimental works. However, they are hard to acquire the corona discharge microphysical processes, which are related to the formation of the current pulse and electromagnetic (EM) wave signals. This article proposes a numerical model with temperature-related transport parameters to study the temperature influence on microphysical processes and current pulses for negative corona. By comparing microphysical quantities such as the effective ionization coefficient, density, and velocity of space charges, the effect of temperature on the current pulse parameters including the rise and fall times, amplitude, and pulsewidth is systematically explained. It shows that as the temperature rises, the current pulse amplitude increases, while the other three parameters decrease. The rise time is dependent on the effective ionization coefficient. The fall time is affected by the velocities of negative and positive ions. The experimental results indicate the simulated current pulses are consistent with the measured ones, proving the effectiveness of the proposed numerical model with temperature variation.

Temporally resolved response of a natural type IIA diamond detector to single-particle excitation