Study On The Linear And Nonlinear Characteristics Of GaAs Photoconductive Switches

Photoconductive Semiconductor Switches(PCSS's) have a very broad prospect of applications in numerous fields such as the generation of high power ultra-wideband pulses and ultra-fast electronics because of their excellent characteristics. GaAs PCSS's have many advantages over others in response speed, the transfer efficiency of light into electricity and high voltage-resistant, especially they can operate in a nonlinear mode with high gain which can reduce the triggering optical energy by 3-5 orders of magnitude comparing to the conventional linear mode. This makes it realistically possible to realize the miniaturization, practicality and integration of the system of PCSS's, therefore they are paid much more attention to. However, up to now, there has been lack of perfect theoretical models for characterization of linear PCSS's, and theoretical explanation of the mechanism of the conduction of nonlinear mode cannot be made very logically. This has seriously hampered the excavation of their application potentials. On account of the status quo for PCSS's home and abroad, the two operational modes of GaAs PCSS's have been investigated theoretically and experimentally in this dissertation. The main contributions are as follows:A numerical model corresponding to the related physical model has been established which can entirely describe the nonlinear operational mode for GaAs PCSS's. The whole course of the variation of characteristics for the nonlinear operational mode of PCSS's in the time domain is tracked by means of simulation and calculation. The details of the dynamic variation of some important electrical parameters have been captured. Very good simulation results have been obtained, which are good agreed with measured output electrical pulse waveforms. As far as we know, such simulation results have not been reported by far.The operation mechanism of deep energy traps in the nonlinear operational mode has been theoretically demonstrated, and the concept of the concentration threshold of deep energy trap has been proposed for the first time. The relation between operational mode and concentration of deep energy trap is quantitatively presented. The existence of ultimate relation between the operational mode and the bias voltage has been argued, and there is a requirement of the threshold of bias voltage as to the nonlinear mode. The quantitative evidences of the existence of close relation between the operational mode and the triggering optical energy has been given, and there exists a requirement of the threshold of triggering optical energy for the nonlinear mode. The main reasons for the different operational modes under the different bias voltage and different triggering /optical energy have well been explained, and the physical essence of the observed threshold of bias voltage and triggering optical energy in the experiment has justly been account for. The relation among the three thresholds of the bias voltage, the triggering optical energy and the concentration of the deep energy level has been studied, and the existence of reverse correlativity among them has been shown. That is to say, increasing the magnitude of one of the three can reduce the thresholds of the other two.The spatial distributions of some important electrical parameters such as electric filed and electric current densities and the dynamical evolvement course of the maximum electric field intensity in the device have been obtained under the different bias voltage, different optical energy and the different concentration of deep energy level trap. This has supplied quantitative supports for explaining the physical mechanism of nonlinear characteristics of PCSS's.Theoretically, an equivalent circuit model for ultrafast linear PCSS's has been proposed. Based on the model, a method for characterizing the performance parameters of linear PCSS's has been presented and the effect of the evolved parameters on the performance parameters of output electric pulses has been investigated. A device model for PSPICE standing for linea...