This paper describes a complete simulation approach to investigating the physics of heayy-ion charge generation and collection during a single event transient in a PN diode. The simulations explore the effects of Werent ion track models, applied biases, background dopings, and LET on the transient responses of a PN diode. The simulation results show that ion track structure and charge collection via diffusiondominated processes play important roles in determining device transient responses. The simulations show no evidence of rapid charge collection in excess of that deposited in the device depletion region in typical funneling time frames (i.e., by time to peak current or in less than 500 ps). Further, the simulations clearly show that the device transient responses are not simple functions of the ion's incident LET. The simulation results imply that future studies and experiments should consider the effects of ion track structure in addition to LET and extend transient charge collection times tb insure that reported charge collection efficiencies include diffusiondominated collection processes.

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This study shows that in the early stages of a single particle transient, the presence of residual holes in the depletion region of a n ϩ p junction affect depletion profile and terminal currents. Due to their greater mobility, electrons deposited in the depletion region move out faster than holes, leaving residual holes in the region. The resulting charge imbalance in the depletion region may cause the depletion region to briefly extend into the substrate before the beginning of recovery process. This extended depletion region influences prompt collection of carriers in the vicinity. In particular, carrier response to this field produces a conduction and/or displacement current. The sum of the conduction plus displacement current is immediately seen as an enhanced prompt conduction current at the device terminals. Enhanced prompt charge collection depends on substrate doping, junction bias, and the density of charge deposited. Low-doped p-type substrates, with longer hole residence time in the depletion region, are more susceptible to enhanced prompt collection and substrate field disturbances. Response of p-Si and n-Si substrates to single event effects and the effects of laser beams for enhanced prompt collection are also analyzed.