Sublinear Current–Voltage Characteristics of Linear Photoconductive Semiconductor Switch

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.