Basic mechanisms for enhanced prompt charge collection in a n⁺p junction following single charged particle interaction

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⁺ 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.