Small-signal analysis of punch-through injection microwave devices

A theoretical small-signal analysis of punch-through injection microwave devices is given. A numerical study of a silicon p +− n− p + structure is performed, which shows good agreement with experimental measurements by Snapp and Weissglas for a diode with a doping density of 1·2 × 10 15/cm 3. Negative resistance is also calculated for diodes with doping densities of 0·6 × 10 15/cm 3 and 5 × 10 15/cm 3. A partially analytical mode, including the lowfield region, is developed and compared with the numerical calculation. Ohmic losses for devices with low impurity concentrations and diffusion for devices with high impurity concentrations are shown to be significant factors. The noise spectrum is calculated numerically from the assumption of two noise sources, injection noise and diffusion noise. The noise measure is determined and shown to be in good agreement with experiments by Björkman and Snapp.