Treatment of soft threshold in impact ionization

The avalanche multiplication and excess noise properties of a range of subm icron Si diodes have been measured and analyzed using a model for impact io nization which includes the effect of dead space, modified to allow for a g radual onset of ionization, with realistic threshold energies. Good agreeme nt is achieved between the predictions of this "soft dead space" model and measurements of multiplication and excess noise, both on a range of submicr on diodes with uniform electric fields and also on a p(+)n diode with a hig hly nonuniform electric field. (C) 2001 American Institute of Physics.