A Method to Maximize the Amplitude of Generated Terahertz Pulse From LT GaAs Photoconductive Semiconductor Switch

The substrate characteristics of GaAs photoconductive switch has been studied in order to determine the conditions required to generate maximum terahertz pulse amplitude in the device. In particular, the substrate material characteristics, such as trap density, capture cross sections, trap occupancy that determine fields, recombination rate, and photogeneration that influence the pulse rise-time in a low temperature grown gallium arsenide semiinsulating material, are studied. Results show that maximum pulse amplitude occurs when the carriers of both polarities contribute to the terminal currents, and the voltage at this point is referred to as the dual injection voltage (DIV). DIV for a given device is directly dependent on the substrate properties as well as the proximity of the electrodes.