半导体断路开关输出预脉冲的产生机理及其参数影响规律

Pre-pulse mechanism and effects of parameters in semiconductor opening switches

半导体断路开关的输出电压中的预脉冲现象,严重影响了整个系统的输出脉冲前沿陡度和重复频率。针对半导体断路开关在反向截断过程中预脉冲产生的过程和机理进行了研究。利用Silvaco Atlas仿真软件对半导体断路开关正反向泵浦过程中载流子的迁移和电场的变化过程进行了详细考察,发现预脉冲的产生是由双边截断过程中N-N^+结截断所引起的脉冲前沿变缓现象,其长短主要取决于P型轻掺杂区内的少子电子的迁移率,而脉冲前沿的陡度则取决于双边截断过程中的PN结截断过程。同时,对具有不同基区长度的器件,对其在不同泵浦电流密度下的情况进行了模拟和对比,发现器件基区越窄,脉冲前沿越陡,而预脉冲基本相等;低电流密度条件下只发生N-N^+结单边截断,大电流密度条件下则发生双边截断,而双边截断的延迟更长,但脉冲前沿拐点更陡,截断更快。

As the key components of all solid-state pulse sources,semiconductor opening switches have the advantages of high frequency,long life,fast interruption,and large power capacity.The pre-pulse in output pulse voltage of semiconductor opening switches seriously affects the pulse rise time and the repetition frequency of the system.In this paper,the mechanism of the pre-pulse during the reverse interruption process is studied.The evolution process of the carriers and the electric field during the forward and reverse pumping processes of the semiconductor opening switches are investigated by using the simulation software Silvaco-Atlas.It is found that the pre-pulse is caused by the N-N^＋junction interruption in the bilateral interruption process.The length of pre-pulse depends mainly on the mobility of minorities in the P-type region,and the slope of the pulse depends on the PN interruption process.Meanwhile,the devices with different base region lengths and different pumping conditions have been simulated and compared.It is found that the device base region is narrower,the pulse rises faster,and the pre-pulse is almost equal with each other.Under low current density conditions,only N-N^＋junction interruption occurs;under high current density,bilateral interruption occurs.The delay of bilateral interruption is longer,but the pulse rises faster.