Properties of Switching Transient in the Semi-Insulating GaAs Photoconductive Semiconductor Switch With Opposed Contacts

The properties of switching transient in the gallium arsenide photoconductive semiconductor switch (GaAs PCSS) are significant for improving the device lifetime. In this article, the properties of switching transient in the opposed-contact semi-insulating (SI) GaAs PCSS, including the physical process of the ultrafast switching, the characteristics of delayed breakdown, and the current density distribution, are studied, based on an effective 2-D, time-dependent numerical model. The numerical results demonstrate that there exists a positive feedback loop between the increase of the carrier density and the formation and evolution of the avalanche domains, which achieves the ultrafast switching of the opposed-contact SI-GaAs PCSS. The higher bias voltage and triggering optical intensity can promote the earlier formation of the avalanche domains and accelerate the evolution of the domains, leading to a shorter delay time and switching time. The triggering positions determine the distribution of the avalanche domains in the opposed structure, affecting the delay time, among which the cathode triggering leads to the shortest delay time. Current crowding in the opposed structure mainly occurs in the vicinity of the contacts, which first damages the edges of the contacts and makes the areas near the contacts present different failure characteristics. Our analysis indicates that anode triggering is effective for suppressing the current crowding to improve the lifetime of the opposed-contact PCSS.