Ultrafast rising of output electric impulse of high gain semi-insulated GaAs PCSS

For the high gain semi-insulated Gallium arsenide (GaAs) photoconductive switches (PCSS), the output current pulse has ultra-fast rise character, the rise time can be even less than that of the trigger laser pulse. So PCSS is the most promising generation of THz radiation because of its character of ultra-fast and high peak power. The experiments result show that the high gain electrical pulse whose rise time is 1.086ns is obtained from GaAs PCSS. The streamer mode is proposed to explain the ultra-fast rise character. The electrical field distortion caused by optically activated charge domain and avalanche impact ionization are the key factors for the streamer formation and propagation. The paper hold the fast propagation of streamer built up the ultra-fast rise character of these switches.