Generalized small-signal analysis of avalanche transit-time diodes

The one-dimensional small-signal analysis of avalanche transit-time diodes with distributed multiplication is reduced to the concept of two layers in cascade, each having a constant ionization rate. The interface is located in the distinguished neutral plane of equal direct electron and hole currents. In this configuration the small-signal problem is characterized by two parameters : namely the location of the neutral plane in the depletion layer and a quantity combining the ionization-rate field dependence and the total direct current density. Normalized admittance diagrams and small-signal growth rates are given which show the relative importance of the low-transit-angle mode where the frequency is smaller than the avalanche resonance frequency and the π mode extending almost to 2π for large current densities. Through a transformation the results are applicable to Read type, abrupt and uniform junctions of Si, Ge, and GaAs avalanche diodes.