雷电间接效应多重脉冲组电流产生装置的设计

针对雷电间接效应多重脉冲组电流模拟需求,完成了雷电间接效应多重脉冲组模拟源的设计,采用20个Crowbar电路支路,通过分时放电的方式实现1个脉冲串内多脉冲输出需求,每个支路可以实现最小间隔30 ms的重复频率放电,从而实现3个脉冲串的输出需求。对放电支路的参数进行了详细设计,分析了电容、波尾电路电感、波尾电路电阻参数变化对输出特性的影响。分析了采用并联大电容实现放电电容重复频率快速充电的可行性,完成了装置的初步结构设计并结合装置结构简要分析了电路模拟参数设置的合理性。该装置建成后,可为电子、电气设备等开展测试提供技术支持。

高储能密度脉冲电容器及固态脉冲形成线试验研究

基于玻璃-陶瓷材料PbO-SrO-Na_2O-Nb_2O_5-SiO_2(PSNNS)制作了脉冲电容器和固态脉冲形成线,其脉冲电容器在工作电压30 kV、放电电流2 kA、重复频率1 kHz下的短路放电寿命大于100万次,储能密度达到0.85 k J/L;制作的满银电极的固态脉冲形成线具有良好的矩形脉冲输出,输出电压脉冲半高宽为45ns。

多通道可延时同步脉冲产生系统研究

为满足高功率脉冲实验中对不同电压等级Marx的触发控制和系统负载对电流的需求,实现脉冲功率的有效叠加,要求在满足系统装置稳定运行的前提下,对每一路脉冲功率单元系统的触发时序达到可精确控制。多通道可延时同步脉冲产生系统针对这一问题,通过对时序逻辑的精确分析以及合理采用FPGA技术,不仅提供产生10路延时电触发信号,而且还能同时产生10路延时光触发信号;在外部10 MHz晶振下,延时范围达到0.1μs^6 ms、延时精度100 ns、步进100 ns;在50Ω负载上实现产生输出幅度>100 V、前沿<14 ns、脉宽>200 ns且各通道之间延时抖动达到≤820 ps的延时同步脉冲。

基于MOSFET的纳秒级全固态脉冲源设计

采用MOSFET半导体固态开关作为主放电开关取代气体开关、高压二极管替代充电电阻的技术方法,设计了一种基于功率MOSFET固态开关的纳秒级全固态脉冲源。设计的脉冲源主开关级数共5级,每级主开关分别由5只功率MOSFET半导体固态开关器件串联组成,开关通断控制采用脉冲隔离变压器同步驱动方式。在重复频率1Hz^1kHz、充电电压4kV、负载阻抗为1kΩ条件下,可实现输出幅度大于20kV、前沿小于10ns且脉宽大于100ns的高压快脉冲。通过实验结果验证了所采用的设计原理及方法的可行性,并给出了单次和重复频率(1kHz)触发信号作用下全固态脉冲源输出的实验结果。

玻璃-陶瓷脉冲形成线的充放电特性

采用熔融-快冷-可控结晶工艺,制备了(Pb,Sr)Nb_2O_6-NaNbO_3-SiO_2大尺寸玻璃陶瓷,开展了其介电性能以及脉冲充放电特性研究。实验结果表明:该玻璃陶瓷材料的介电常数约为340,具有良好的温度稳定性和正的偏压特性。基于该材料制备的固态脉冲形成线输出脉冲脉宽约为89ns,具有良好的脉冲平顶和窄的上升沿。在19kV充放电电压、1kHz的充放电频率、4kA的放电电流条件下,固态脉冲形成线充放电寿命大于100万次。

模块化多路同步快脉冲触发源设计

基于超快速高压大功率半导体开关、脉冲形成电路以及同心等间距传输的关键技术,提出一种模块化多路同步快脉冲触发源技术方案。设计出在负载阻抗为50Ω时,可同步输出两种快脉冲触发信号:一种幅度大于20V(4路)、脉冲前沿小于820ps、脉冲宽度大于100ns;另一种则是幅度大于100V(4路)、前沿小于1.4ns、脉宽大于100ns;在外触发作用下,触发源系统抖动和脉冲输出同步分散性分别达到2ns和36.6ps。电路结构上充分利用等间距电信号传输的原理,实现了快脉冲触发源模块化的设计。通过实验结果验证了所采用的设计原理及方法的可行性,给出了在外触发脉冲单次和重频(5kHz)作用下该同步快脉冲触发源输出的实验结果。

特种电源技术研究进展概述

特种电源技术是电源技术研究领域中极为活跃的研究方向,与存在广泛市场需求的通用电源技术相比,其与物理、化学、材料科学与工程、环保、生物医学、高新装备、航空航天等科研、军事、工程领域的发展关系更为紧密。近年来,在大科学工程、高新装备等的需求推动下,特种电源技术研究综合应用电工、电子、材料和计算机技术等多个学科的科技成果取得显著技术进步,研发投入和产业规模迅速增长。本文结合流体物理研究所特种电源研究成果,对特种电源近年来的研究进展作简要分析。

基于伪火花开关控制的脉冲氙灯电源研究

为满足爆轰试验高速摄影测试技术中脉冲氙灯照明系统的需求,设计了一种充电电压0～15 kV、储能电容100μF、可分别驱动规格为φ20 mm×500 mm×620 mm和φ50 mm×720 mm×1 080 mm两种脉冲氤灯的电源。采用在光触发信号作用下,一是将高压触发源输出15 kV的脉冲信号,通过绕丝方式对脉冲氙灯进行启辉使其瞬间导通;二是利用伪火花开关（PSS）导通机理将存储在电容上的能量,经电感后迅速转移到脉冲氤灯上对其放电即点亮氙灯。最终在两种脉冲氙灯上分别得到电压约5 kV,15 kV,电流3 kA,8 kA、发光持续时间分别为200μs和100μs的脉冲信号。通过实验结果验证所采用的设计原理及方法的可行性,并给出实验结果。

用于等离子体射流装置的高压变频脉冲源研究

为研究某种等离子体射流装置在常温常压空气中的放电特性,设计了一种可输出准正弦波电压幅度最高为20 kV、重复工作频率1 Hz~100 kHz可调,功率约为5 kW的等离子体高压变频脉冲源。设计上采用金属-氧化物半导体场效应晶体管(MOSFET)构建全桥拓扑电路,利用开关电源软开关技术原理,将初级能量转移到全桥式串联谐振逆变器上,通过控制芯片施加驱动脉冲信号,经高频脉冲变压器变换后输出高幅度脉冲电压。在间歇或连续工作模式下,该脉冲源输出的高压准正弦波脉冲信号,被加载至等离子体射流装置上,该装置经高压脉冲作用下击穿放电后产生等离子体射流。通过实验结果验证了所采用的设计原理及方法的可行性,给出了不同工作频率条件下得到的实验结果。

砷化镓光导开关的损伤形貌研究

制作了同面型砷化镓光导开关,并测试了其导通性能。在偏置电压8 kV、激光能量10 mJ、重复频率10 Hz的条件下,研究了光导开关触发104次后器件表面的损伤形貌。利用激光扫描共聚焦显微镜,对电极边缘及电极间的损伤形貌进行分析,研究发现阳极边缘由于热积累形成热损伤,而阴极边缘的热损伤来源于热应力,并对电极间损伤形貌进行细致表征及分类。

基于多种检测手段的高压电缆头绝缘放电诊断分析

高压电缆头制作由于结构封闭、部件复杂以及电场均匀度要求高,一直是一个难题。在利用红外精确测温、超声波和高频电流局放检测法的基础上,创新性地引入了X射线吸收衬度成像技术对电力电缆头进行无损检测。通过多种检测手段综合诊断及解体论证,对一起35 kV单芯高压电力电缆头绝缘放电案例进行了详细分析。分析结果表明:X射线吸收衬度成像技术能够有效辅助查找高压电缆头在制作或使用中老化产生的孔洞、裂缝等缺陷;多种检测方式相互验证,可以提高缺陷定性分析的准确率。文中率先将X射线吸收衬度成像技术应用于工程现场,实现通过图形查找高压电缆头故障缺陷,提高电力电缆故障诊断直观性和可靠性。

Influence of Hot-Carriers on the On-State Resistance in Si and GaAs Photoconductive Semiconductor Switches Working at Long Pulse Width

We demonstrate that the transport of hot carriers may result in the phenomenon where an oscillated output current appears at the waveforms in a high-power photoconductive semiconductor switch(PCSS) working at long pulse width when the laser disappears or the electric field changes. The variational laser and electric field will affect the scattering rates of hot carriers and crystal lattice in high-power PCSS, and the drift velocity of hot carriers and also the on-state resistance will be changed. The present result is important for reducing the on-state resistance and improving the output characteristics of high-power Si/Ga As PCSS.

Effects of GaN cap layer thickness on an AlN/GaN heterostructure

In this study, we investigate the effects of Ga N cap layer thickness on the two-dimensional electron gas(2DEG)electron density and 2DEG electron mobility of Al N/Ga N heterostructures by using the temperature-dependent Hall measurement and theoretical fitting method. The results of our analysis clearly indicate that the Ga N cap layer thickness of an Al N/Ga N heterostructure has influences on the 2DEG electron density and the electron mobility. For the Al N/Ga N heterostructures with a 3-nm Al N barrier layer, the optimized thickness of the Ga N cap layer is around 4 nm and the strained a-axis lattice constant of the Al N barrier layer is less than that of Ga N.

Different influences of Schottky metal on the strain and relative permittivity of barrier layer between AlN/GaN and AlGaN/GaN heterostructure Schottky diodes

Ni/Au Schottky contacts on AlN/GaN and AlGaN/GaN heterostructures are fabricated.Based on the measured current–voltage and capacitance-voltage curves,the polarization sheet charge density and relative permittivity are analyzed and calculated by self-consistently solving Schrdinger’s and Poisson’s equations.It is found that the values of relative permittivity and polarization sheet charge density of AlN/GaN diode are both much smaller than the ones of AlGaN/GaN diode,and also much lower than the theoretical values.Moreover,by fitting the measured forward I–V curves,the extracted dislocations existing in the barrier layer of the AlN/GaN diode are found to be much more than those of the AlGaN/GaN diode.As a result,the conclusion can be made that compared with AlGaN/GaN diode the Schottky metal has an enhanced influence on the strain of the extremely thinner AlN barrier layer,which is attributed to the more dislocations.

Influence of Schottky drain contacts on the strained AlGaN barrier layer of AlGaN/AlN/GaN heterostructure field-effect transistors

Rectangular Schottky drain AlGaN/AlN/GaN heterostructure field-effect transistors (HFETs) with different gate contact areas and conventional AlGaN/AlN/GaN HFETs as control were both fabricated with same size. It was found there is a significant difference between Schottky drain AlGaN/AlN/GaN HFETs and the control group both in drain series resistance and in two-dimensional electron gas (2DEG) electron mobility in the gate-drain channel. We attribute this to the different influence of Ohmic drain contacts and Schottky drain contacts on the strained AlGaN barrier layer. For conventional AlGaN/AlN/GaN HFETs, annealing drain Ohmic contacts gives rise to a strain variation in the AlGaN barrier layer between the gate contacts and the drain contacts, and results in strong polarization Coulomb field scattering in this region. In Schottky drain AlGaN/AlN/GaN HFETs, the strain in the AlGaN barrier layer is distributed more regularly.

Influence of thermal stress on the relative permittivity of the AlGaN barrier layer in an AlGaN/GaN heterostructure Schottky contacts

Ni Schottky contacts on AlGaN/GaN heterostructures were fabricated.Some samples were thermally treated in a furnace with N 2 ambience at 600 C for different times (0.5 h,4.5 h,10.5 h,18 h,33 h,48 h,and 72 h),the others were thermally treated for 0.5 h at different temperatures (500℃,600℃,700℃,and 800℃).With the measured current-voltage (I-V) and capacitance-voltage (C-V) curves and by self-consistently solving Schrodinger's and Poisson's equations,we found that the relative permittivity of the AlGaN barrier layer was related to the piezoelectric and the spontaneous polarization of the AlGaN barrier layer.The relative permittivity was in proportion to the strain of the AlGaN barrier layer.The relative permittivity and the strain reduced with the increased thermal stress time until the AlGaN barrier totally relaxed (after 18 h at 600℃ in the current study),and then the relative permittivity was almost a constant with the increased thermal stress time.When the sample was treated at 800℃ for 0.5 h,the relative permittivity was less than the constant due to the huge diffusion of the contact metal atoms.Considering the relation between the relative permittivity of the AlGaN barrier layer and the converse piezoelectric effect,the conclusion can be made that a moderate thermal stress can restrain the converse piezoelectric effect and can improve the stability of AlGaN/GaN heterostructure devices.

Influence of thermal stress on the characteristic parameters of AlGaN/GaN heterostructure Schottky contacts

Ni Schottky contacts on AlGaN/GaN heterostructures have been fabricated. The samples are then thermally treated in a furnace with N 2 ambient at 600 C for different times (0.5,4.5,10.5,18,33,48 and 72h). Current-voltage (I-V ) and capacitance-voltage (C-V ) relationships are measured,and Schrodinger's and Poisson's equations are self-consistently solved to obtain the characteristic parameters related to AlGaN/GaN heterostructure Schottky contacts: the two-dimensional electron gas (2DEG) sheet density,the polarization sheet charge density,the 2DEG distribution in the triangle quantum well and the Schottky barrier height for each thermal stressing time. Most of the above parameters reduce with the increase of stressing time,only the parameter of the average distance of the 2DEG from the AlGaN/GaN interface increases with the increase of thermal stressing time. The changes of the characteristic parameters can be divided into two stages. In the first stage the strain in the AlGaN barrier layer is present. In this stage the characteristic parameters change rapidly compared with those in the second stage in which the AlGaN barrier layer is relaxed and no strain is present.

Influence of the channel electric field distribution on the polarization Coulomb field scattering in In_(0.18) Al_(0.82) N/AlN/GaN heterostructure field-effect transistors

By making use of the quasi-two-dimensional(quasi-2D) model, the current–voltage(I–V) characteristics of In0.18Al0.82N/AlN/GaN heterostructure field-effect transistors(HFETs) with different gate lengths are simulated based on the measured capacitance–voltage(C–V) characteristics and I–V characteristics. By analyzing the variation of the electron mobility for the two-dimensional electron gas(2DEG) with electric field, it is found that the different polarization charge distributions generated by the different channel electric field distributions can result in different polarization Coulomb field scatterings. The difference between the electron mobilities primarily caused by the polarization Coulomb field scatterings can reach up to 1522.9 cm2/V·s for the prepared In0.18Al0.82N/AlN/GaN HFETs. In addition, when the 2DEG sheet density is modulated by the drain–source bias, the electron mobility presents a peak with the variation of the 2DEG sheet density,the gate length is smaller, and the 2DEG sheet density corresponding to the peak point is higher.

Determination of the series resistance under the Schottky contacts of AlGaN/AlN/GaN Schottky barrier diodes

Rectangular AlGaN/AlN/GaN heterostructure field-effect transistors (HFETs) were fabricated,and the gate and the source of the HFETs consisted of AlGaN/AlN/GaN Schottky barrier diodes (SBDs).Based on the measured forward current-voltage and the capacitance-voltage characteristics of the AlGaN/AlN/GaN SBDs,the series resistance under the Schottky contacts (RS) was calculated using the method of power consumption,which has been proved to be valid.Finally,the method of power consumption for calculating R S was successfully used to study the two-dimensional electron gas electron mobility for a series of circular AlGaN/AlN/GaN SBDs.It is shown that the series resistance under the Schottky contacts cannot be neglected and is important for analysing and characterizing the AlGaN/AlN/GaN SBDs and the AlGaN/AlN/GaN HFETs.

A simple method of extracting the polarization charge density in the AlGaN/GaN heterostructure from current-voltage and capacitance-voltage characteristics

An Ni Schottky contact on the AlGaN/GaN heterostructure is fabricated. The flat-band voltage for the Schottky contact on the AlGaN/GaN heterostructure is obtained from the forward current-voltage characteristics. With the measured capacitance-voltage curve and the flat-band voltage, the polarization charge density in the AlGaN/GaN heterostructure is investigated, and a simple formula for calculating the polarization charge density is obtained and analyzed. With the approach described in this paper, the obtained polarization charge density agrees well with the one calculated by self-consistently solving Schrodinger's and Poisson's equations.