Numerical simulation of spatially nonuniform switching in silicon avalanche sharpening diodes

The process of spatially nonuniform switching in high-voltage silicon diodes operating in the delayed avalanche regime has been numerically simulated. The dependence of the transient process on the ratio between the total diode cross-section area and the area of the region where the switching takes place has been studied. The switching time (60–70 ps) and qualitative form of the transient characteristic agree with the available experimental data. It is established that a rapid drop of the diode voltage begins after the ionization front has traveled over most of the base and then continues due to secondary avalanche breakdown of the base filled with free carriers. Thus the time of switching to the conducting state exhibits no direct correlation with the velocity of ionization front propagation.