Sublinear Current–Voltage Characteristics of Linear Photoconductive Semiconductor Switch

摘要

This letter presents the measurement of photoconductive semiconductor switch (PCSS) based on semi-insulating (SI) GaAs in its linear mode, through which output voltage saturation and sublinear current–voltage characteristics were obtained. The measurements of its dark-state characteristics were also taken to explore the underlying physical mechanism. Both the resistance and free-carrier concentration of ON-state and dark-state PCSS were extracted and analyzed. Remarkable contrasts between the resistance characteristics and obvious parallels for the features of free-carrier density indicate that the sublinear current–voltage characteristics of PCSS are related to the negative differential mobility and the native defect EL2 levels of SI GaAs. The sublinear current–voltage characteristics and the saturation of output voltage exhibited in terahertz pulse generator based on GaAs PCSS are ascribed to the intrinsic characteristics of PCSS.