高压GaAs光导开关的锁定及延迟效应机理分析

Analysis of Lock-On and Time Delay in High-Voltage GaAs PCSS′s

利用二维器件模拟程序MEDICI对GaAs光导开关 (PCSS′s)的动态非线性特性 ,特别是高场下呈现出的锁定及延迟效应的工作机制进行了仿真研究。仿真结果表明深能级陷阱能显著影响开关中的电场、载流子、电流密度等分布 ,引起电流的延迟 ,使开关中某些区域的电场动态增强 ,并足以达到雪崩的强度 ,从而引起载流子雪崩倍增 ,并在外电路的作用下 ,使开关进入锁定状态。仿真结果与实验现象基本相符 ,由此得出结论 :高压GaAs光导开关实验中所观察到的锁定及延迟等现象均与开关材料中故意或非故意引入的深能级陷阱密切相关。

A simulation of dynamic nonlinear characteristics of high-voltage optically controlled photoconductive semiconductor switches (PCSS's) is performed with 2-D simulator MEDICI, and the emphasis is put on the mechanism of lock-on and time delay under high electric field condition. It is found that the deep energy levels play an important role in lock-on and time delay. They can dynamically change the distribution of electric field, carriers and current densities in PCSS's, cause output current to delay and also strengthen the local electric field enough to cause avalanche. The simulated results agree with experimental ones. It is concluded that the observed nonlinear characteristics are closely related to the introduced deep energy levels in PCSS's.