Simulation Of Laser Induced Charge Domain Evolution And Design Of A Quenched Photoconductive Switch

A photoconductive semiconductor switches(PCSS),as the core device of a high-power and high-repetition-frequency ultra-fast electric pulse source,has a wide of applications prospects in the terahertz technology,the ultra-wideband communication,the underground sensing,the controlled nuclear fusion,the gas pedals,the shock radar,the ultra-wideband electromagnetic interference weapons,the high current ignition and so on.In this dissertation a high-gain quenched(HGQ)PCSS structure is proposed,which operates in the high-gain quenched mode under the control of a gate pulse and a low-energy laser pulse,The device characteristics not only have the advantages such as the low optical excitation energy and the ultra-fast rise edge of a traditional PCSS in the high-gain mode,but also have the advantages such as the high repetition frequency and the long service life of the traditional PCSS in the linear mode.The detail is as follows:Firstly,the models of the high-field mobility with the negative differential mobility region,the impact ionization,the carrier recombination and the optical recombination/generation are considered to build the device simulation model of pulsed laser-activated charge domains in a semi-insulating GaAs:EL2 substrate.The evolution of "a photo-activated charge domain→luminescent domains avalanche luminescent domains" is simulated and observed from a microscopic point of view,and then the sensitive factors to quench the avalanche luminescent domains are analyzed.It is helpful the design of a GaAs:EL2-base HGQ PCSS.Secondly,the HGQ PCSS is designed with a MISFET cell array mading of the four homoepitaxy-epitaxy layers on a semi-insulated GaAs:EL2 substrate.The quenching operation principle is that,the electric field across the avalanche luminescent domains is redistributed since the withdrawal of the gate voltage causes to rupidly expand the PN junction space charge region,and hence the carrier high gain prerequisite becomes to dissatisfying.A half-cell device simulation model is built and compared with a traditional PCSS with the same substrate.The static and the dynamic characteristics are simulated and analyzed.The simulation results show that,the bias voltage maximum of the HGQ-PCSS is 4.8 kV,the optimum bias voltage to maintain the dynamic balance of the avalanche luminescence domains is 4 kV,the static leakage current is 6 orders of magnitude lower than the traditional PCSS,the quenching time is less than 20 ns with a gate-voltage drop rate of 0.5 V/ns,and the maximum repetition frequency is in the order of 10 MHz.Finally,the performance effects from the laser and the device design parameters are analyzed.The main sensitive parameters are optimized and the objectives of suppressing the photocurrent spikes and reducing the epitaxial cost of the device are achieved.