Photoexcited carrier dynamics in a GaAs photoconductive switch under nJ excitation

In this article, the bunched transport of photoexcited carriers in a GaAs photoconductive semiconductor switch (PCSS) with interdigitated electrodes is investigated under femtosecond laser excitation. Continuous outputs featuring high gain are obtained for single shots and at 1 kHz by varying the optical excitation energy. An ensemble three-valley Monte Carlo simulation is utilized to investigate the transient characteristics and the dynamic process of photoexcited carriers. It demonstrates that the presence of a plasma channel can be attributed to the bunching of high-density electron–hole pairs, which are transported in the form of a high-density filamentary current. The results provide a picture of the evolution of photoexcited carriers during transient switching. A photoinduced heat effect is analyzed, which reveals the related failure mechanism of GaAs PCSS at various repetition rates.