Carrier Transport and Pulse Compression of an Opposed-Contact GaAs Photoconductive Switch at Low-Energy Optical Excitation

The photoconductive semiconductor switch (PCSS) is one of the most promising devices in pulsed power technology, and its transient output characteristics strongly depend on the internal photo-generated carrier transport. In this paper, the transient output characteristics of an opposed-contact GaAs PCSS are obtained at 3.0-5.35 kV at low-energy optical excitation. In contrast to the 8 ns optical pulse, the pulse width of the switching waveform is compressed to 2.2 ns, corresponding to a compression ratio of 72%. The electric field threshold of 38 kV/cm is verified for the pulse compression effect (PCE) in our experiment. The maximum output amplitude is 2.27 kV with a 660 ps rise time, and the relevant transmission efficiency is 43.7%. The transient electric field distribution of the GaAs PCSS at the bias voltage corresponding to the PCE is simulated by a two-dimension model. The influence of carrier transport on pulse compression is analyzed numerically during the spatiotemporal variation of the electric field. Results indicate that the PCE is attributed to the negative differential mobility (NDM) effect and the electric field shielding (EFS) effect. The characteristics of an ultrafast, compressed pulse, along with the increased output, provide the specific guidance for high-power applications at high repetition rates.