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实验用波长1064nm,触发光能为1.0mJ的激光脉冲触发电极间隙为4mm的半绝缘GaAs光电导开关,当光电导开关的偏置电压达到3800V时,开关进入非线性(lock-on)工作模式,在偏置电场和触发光能不变的条件下,开关输出稳定的非线性电脉冲,1500次触发后GaAs开关表面出现因丝状电流引起损伤的痕迹.分析认为:在一定触发光能和电场阈值条件下,开关芯片内存在两种瞬态热效应:热弛豫效应和光激发电荷畴-声子曳引效应.热弛豫时间很短,在皮秒甚至亚皮秒量级,热弛豫过程导致了热传导的弛豫行为;当光激发电荷畴以107cm/s的速度从阴极向阳极渡越时,在这两种效应的作用下使得开关芯片瞬态温度变化发生了弛豫振荡现象.光激发电荷畴-声子曳引效应在位错运动方向上传播,声子流携带的热能集中在移动的平面内,使得移动区域温度升高,移动轨迹经多次叠加累积呈现出丝状的损伤痕迹.
Experiments with a wavelength of 1064nm, the trigger light energy of 1.0mJ laser pulse trigger electrode gap of 4mm semi-insulating GaAs photoconductive switch, when the photoconductive switch bias voltage reaches 3800V, the switch into the lock-on mode , Under the condition that the bias electric field and the triggering light energy are not changed, the switch outputs a stable non-linear electric pulse, and the traces of the filament current caused by the filament current appear on the surface of the GaAs switch after 1500 shots.According to the analysis, Under the threshold of electric field, there are two kinds of transient thermal effects in the switch chip: thermal relaxation effect and photoexcited charge-domain-phonon-trapping effect.The thermal relaxation time is very short, and in the picosecond or even sub-picosecond order, thermal relaxation The process leads to the relaxation behavior of the thermal conduction. When the photoexcited charge domain traverses from the cathode to the anode at a rate of 107 cm / s, the transient oscillations of the switch chip occur under the action of these two effects. The photo-excited charge-domain-phonon-trapping effect propagates in the direction of dislocation motion, and the thermal energy carried by the phonon flow is concentrated in the moving plane, causing the temperature in the moving region to increase. The moving trajectory accumulates in a filamentous damage Track.