Abstract: A mode for the periodicity and weakening surge in semi-insulating GaAs photoconductive semiconductor switches is proposed based on the transferred-electron effect.It is shown that the periodicity and weakening surge is caused by the interaction between the self-excitation of the resonant circuit and transferred electron oscillation of the switch.The bias electric field (larger than Gunn threshold) across the switch is modulated by the AC electric field,when the instantaneous bias electric field E is swinging below Gunn electric field threshold ET but greater than the sustaining field ES (the minimum electric field required to support the domain) at the time of the domain reaching the anode,and then the delayed-dipole domain mode of switch is obtained.It is the photon-activated carriers that satisfy the requirement of charge domain formation on carrier concentration and device length product of 1e12cm-2,and the semi-insulating GaAs photoconductive semiconductor switch is essentially a type of photon-activated charge domain device.

Key words: semi-insulating GaAs photoconductive switch, Gunn effect, self-excitation, delayed-dipole domain mode