Compensation mechanisms and the response of high resistivity GaAs photoconductive switches during high-power applications

Photoconductive semiconductor switches (PCSSs) made from semi-insulating (S I) GaAs are the primary switching component of one class of high-power, ult ra-wideband (UWB) microwave sources, The high resistivity of the GaAs can h e achieved through different processing techniques. The resultant device ch aracteristics of the PCSS such as breakdown voltage, rise time, and turn-on delay will depend on the actual processing technique that was used for the material. Simulation studies comparing an intrinsic material and a high re sistivity SI GaAs PCSS grown through the liquid-encapsulated Czochralski (L EC) process with a deep donor and shallow acceptor compensation mechanism h ighlight these differences. Simulations also elucidate the role of an n(+)- doped layer placed next to the cathode, which increases the breakdown volta ge of the device. Extending the n(+) layer length beyond the cathode does n ot yield further improvement but leads to current confinement along a narro w strip that can initiate local heating or burnout. The doping profile of t he n(+) layer also affects hold-off characteristics, a faster gradient ensu ring better protection of the cathode against the substrate field, and elec tron injection. Doping the n(+) region with a higher concentration of carbo n impurities does not produce the same effect as doping the n(+)-SI interfa ce, These material-related issues are critical to further extending the per formance characteristics of PCSSs.