Monopole Charge Domain in High-Gain Gallium ArsenidePhotoconductive Switches

Abstract

Considering that semi-insulating galliumarsenide photoconductive switches can be triggered into the high gainmode and no reliable theories can account for the observed transientcharacteristics, we propose the monopole charge domain model to explainthe peculiar switching phenomena occurring in the high gain mode and wediscuss the requirements for the lock-on switching. During operation onthis mode, the applied field across the switch and the lock-on fieldare all larger than the Gunn threshold field. Our developed monopolecharge domain is based on the transferred-electron effect, but thedomain is only composed of large numbers of electrons piled up due tothe negative differential mobility. Using the model and taking thephysical mechanism of the avalanche impact ionization and recombinationradiation into consideration, we interpret the typical phenomena ofthe lock-on effect, such as the time delay between the beginning of opticalillumination and turning-on of the switch, and the conduction mechanism of thesustaining phase. Under different conditions of bias field intensityand incident light energy, the time delay of the switching iscalculated. The results show that the physical mechanisms of impactionization and recombination radiation occurring in the monopole chargedomain are responsible for the lock-on switching.