The Research Of GaAs PCSS Timing Jitter And The Positive And Negative Symmetrical Output With Fast Front

GaAs photoconductive semiconductor switch(PCSS)which comprises a photoconductive semiconductor and an ultra-fast laser is one of the most promising devices in the fields of ultra-fast electronics,pulsed power and terahertz technology.When there is a need for a combination of ultra-fast rising edge,free triggering jitter,ultra-short pulse width,high repetition frequency,high power and anti-electromagnetic interference,a photoconductive semiconductor switch is the optimal selection for a power switch.In the dissertation,the factor of influencing the jitter time of GaAs PCSS and fast frontier output positive and negative symmetry using GaAs PCSS are discussed.In this paper,the specific do the following:(1)The analysis shows the scattering rate,the spatial distribution and time distribution of the photo-generated carrier concentration have a direct effect on the electric conductivity and timing jitter of the PCSS by the working principle.The scattering of the carrier as well as production and compound are random process which cause the jitter time as the switch conduction.In this dissertation,the laser is split into two optical beams by a cross grating to excite two 3mm gap GaAs PCSSs in parallel at the same time.The jitter time of our GaAs PCSS decreases from 0.94 ns to 0.40 ns as the trigger laser pulse width decreases from 30 ns to 11 ns.That is,the jitter time of the GaAs PCSS reduces as the trigger laser pulse width decreases.The formula of timing jitter in GaAs PCSS is deduced according to the probability distribution of the output electrical pulse and the corresponding relation between the time and electrical waveform In theory,when the trigger laser is equal,the gradient of the current waveform at half of the rising edge increases as the trigger laser pulse width decreases.Therefore,the jitter time of GaAs PCSS decrease accordingly.It is pointed out laser pulse width is a dominat factor which affect the timing jitter of GaAs PCSS.(2)The up-and-down of trigger light wave amplitude affect the output electrical pulse amplitude fluctuation.From the experiment result,the fluctuation of laser pulse energy has a linear relationship with the output electrical pulse amplitude fluctuation.Test the jitter time of GaAs PCSS with 3 mm gap when the laser pulse energy increases from 0.40 mJ to 1.60 mJ.The jitter time decreases from 0.68 ns to 0.38 ns as the incident pulse energy increases from 0.40 mJ to 1.6 mJ.When the laser pulse width is fixed,the carriers number in unit time increases as the laser pulse energy increase.As the same time,the relative deviation decreases when the laser pulse energy increases.Therefore,the jitter time of GaAs PCSS decrease accordingly.(3)The authors used 1064 nm and 532 nm laser pulses to investigate the timing jitter in a GaAs photoconductive switch with 2 mm gap.As laser pulse energy increases from ten odds ?J and hundreds ?J,the jitter time of GaAs PCSS triggered by 1064 nm pulse wavelength laser decreased from 96.4 ps to 86.6 ps and by 532 nm pulse wavelength laser decreased from71.6 ps to 63.3 ps.The conclusion is that under excitation of a laser pulse,the jitter decreases significant as the laser wavelength decreases.It is pointed out that the shallower the absorption depth is,the more the carriers number in unit time.Thus,it is found that jitter is closely linked to the absorption depth of the GaAs,the weaker absorption corresponds to a smaller jitter.(4)It used a femotosecond laser pulse to trigger GaAs PCSS with a gap of 2.5 mm and 3.5 mm.The positive and negative bilateral electrical pulse with 149 ps rise time and 92.9%voltage transmission efficiency output symmetrically by differerent capacitive storage.In addition,when the bias voltage is ±1700 V,the laser pulse with 99 ?J energy and the 1kHz frequency triggers GaAs PCSS.According to the 10 times overlap of output electrical pulse,GaAs PCSS operates at linear mode despite laser pulse energy and bias electrical field are greater than the nonlinear moder thereshold.It is due to the load resistance and GaAs PCSS share the bias volage together.