Experiment of a lateral semi-insulating GaAs photoconductive semiconductor switch (SI-GaAs PCSS) with different
electrode gaps triggered by 900nm semiconductor laser is reported. With the biased voltage of 0.2KV~3.0KV, the linear
electrical pulse is outputted by SI-GaAs PCSS. When laser energy is very low, the semi-insulating GaAs PCSS with
1.5mm electrode gap is triggered by laser pulse, the output electrical pulse samples is instable. When the energy of the
laser increases, the amplitude and the width of the electrical pulse also increase. It indicates that a stable electrical pulse
is obtained while laser energy is high. With the biased voltage of 2.8kV, the SI-GaAs PCSS with 3mm electrode gap is
triggered by laser pulse about 10nJ in 200ns at 900nm. The SI-GaAs PCSS switches a electrical pulse with a voltage up
to 80V. The absorption mechanism by Franz-Keldysh effect under high-intensity electric field and EL2 deep level
defects is discussed.
The structure and working mechanism of a photoconductive photodetector are compared with a p+-i-n+ (PIN) photodiode
and a metal-semiconductor-metal (MSM) photodetector which is regarded as two back-to-back Schottky barrier
photodiodes. Because a photoconductive photodetector has the features of high critical field strength, especially no
junction capacitance and no dead zone, it has the main merits of high signal-noise ratio, ultrafast response and high
quantum efficiency. We fabricate two photoconductive photodetectors in a lateral configuration on a semi-insulating (SI)
gallium arsenide (GaAs) wafer, which wavelength range of response is from UV to 1.73μm due to two-photon
absorption. It is shown by the volt-ampere characteristics curve that the dark leakage current of 30μm-gap SI GaAs
photoconductive photodetector at a bias field of 66 V/cm is less than 1.2 μA. Our experiment has demonstrated that SI
GaAs photoconductive photodetectors are noteworthily superior to high-speed Si PIN photodetectors to measure
ultrashort pulse lasers with the properties of ultrafast response, ultrawide spectral range, high signal-noise ratio and ease
Experiments of a lateral semi-insulating GaAs photoconductive semiconductor switch triggered by nanosecond serial laser pulses were reported. The switches were insulated by solid multi-layer transparent dielectrics. Jitter-free electrical pulses with steady voltage amplitude from the 0.5 mm-gap GaAs switches were observed. Its change of amplitude was less than 1.1%, the triggered jitter-time was less than 10ps, and pulse width was up to sub-nanosecond. The Jitter-free and steady speciality of electrical pulses from the photoconductive semiconductor switch was analyzed. It was indicated that ultra-fast electrical pulse with steady voltage amplitude and pico-second triggered jitter-time can be obtained by controlling switch trigger condition and optimizing switch design.
Monte-Carlo method is adopted in GaAs PCSS's simulation, In the case of high optical fluence, space-charge field can intensity influence the movement of the carrier. Thus, space-charge field can intensity influence not only the shape of photo-electric current of PCSS's, but also the terahertz out put of photo-conducting antenna. In this paper, the forming and movement of space-charge field are simulated by means of Monte-Carlo method. And the result of simulate indicates that optically activated charge multi-domain exists in photoconductor. The forming of multi-domain is also explained in this paper.