Dark current characterization of photoconductive switches

Abstract

Dark current characterization of GaAs photoconductive switches is examined with an emphasis on low frequency current oscillations caused by travelling charge domains in the semiconductor. The voltage controlled negative differential resistance responsible for this phenomenon is due to field enhanced capture of deep level traps and is utilized for extraction of trap parameters using simple thermionic measurements. The GaAs switch investigated is of the avalanche variety and has been shown to produce current filament.ation in the on state. Since this latter effect is associated with a current controlled negative differential resistance region, we speculate on the nature of the transition between the two states.

Lock-on physics in semi-insulating GaAs: Combination of trap-to-band impact ionization, moving electric fields and photon recycling

“…Experimental observations of GaAs photoconductive semiconductor switches (PCSS) have shown the presence of nonuniformities in the electric field, 11 filamentary current flow when operated at fields above $10 kV/cm (Ref. 12) and a "Lock-On" effect. 13 lock-on, which occurs when the switch is operated above a characteristic average electric field, results in a continuous flow of current even after the termination of the external optical pulse.…”

Roles of voltage in semi-insulating GaAs photoconductive semiconductor switch

“…[7][8][9] Conversely, the increase in leakage current at high voltage can degrade the high resistivity of PCSS, [7] and then the lifetime, [10] which is one of the important issues for highgain PCSS. [6] Many efforts have been made to study the dark current-voltage characteristics to emphasize performances of GaAs PCSS, such as current oscillations of low frequency, [11] the effects of different geometries, [12] and the response time of PCSS at high voltage bias. [13] Always seen as a constant, the dark resistance has not been taken into account in those researches.…”