Theoretical optimization of EBS targets

The analysis of the external circuit response and internal behavior of an electron-bombarded semiconductor diode (EBS target) has been extended using static and dynamic computer simulation techniques. This work complements the previous simplest case analytical treatment of target operation and makes possible the accurate evaluation of high-level target response with any or all of the following effects: arbitrary input current waveform; arbitrary pair-creation profile corresponding to arbitrary values of incident electron energy and drift-region width; operation where both electrons and holes contribute significantly to the target current; electric-field-dependent carrier drift velocities; arbitrary profile of drift-region doping; and effects due to carrier diffusion and recombination. Operation of the computer programs is briefly described for the static and time-dependent cases. Output waveforms and time-varying internaI electric field profiles are shown for two representative cases that violate the assumptions of the simplest case analytical treatment. The first target design shows that 500 A of output current can be switched into a 0.5-Ω load with 0.5-ns risetime. The second target design illustrates the effects that occur when the beam-generated electron-hole pair creation extends completely across the drift region. The analysis of this target also shows that current pulses of 30 A can be switched with a 40-ps risetime into a 1.4-Ω load. A comparison with experimental results shows good agreement under static and dynamic conditions.