Rise time considerations for photoconductive switch materials used in high power UWB microwave applications

Summary form only given. Because of its high resistivity undoped semi-insulating (SI) GaAs grown through the liquid encapsulated Czochralski technique has been used as photoconductive semiconductor switches (PCSS) in high power applications. In such cases, the device can withstand an off-state voltage in excess of 20 kV, which can then be transferred to the load during the on state. We present results from the simulation studies of an ´opposed´ contact PCSS, made from EL2/C compensation and compare it with an intrinsic GaAs material. The study presents physical conditions inside the device during the switching operation and looks into the possible effects of low doping verses high resistivity through compensation on the switch rise time. Preliminary results show that the non-compensated (intrinsic) materials behave as ´relaxation´ semiconductors and the recombination mechanism tends to have an adverse effect on the rise time of the device. Effects of bias on the rise time are also investigated.