Charge Collection Measurements for Heavy Ions Incident on n- and p-Type Silicon

We present the results of charge collection measurements for heavy ions incident on n- and p-type silicon for a range of doping densities and bias conditions. The total collected charge agrees reasonably well for most particles with the simple model we presented last year. However, the model begins to break down for very highly ionizing particles. The experiments also indicate that the collection time increases with ionization density, so that significant recovery of the struck junction may occur during the collection process. We also found that recombination is only a small effect; and the charge collection does not seem to depend strongly on angle of incidence, at least for the cases where we performed measurements. We discuss the implications of all these findings for circuits operating in a cosmic ray environment.