Analysis of the Effect of Fast-Neutron Bombardment on the Current-Voltage Characteristic of a Conductivity-Modulated p-i-n Diode

Fast-neutron bombardment of silicon diodes changes the excess carrier diffusion length without significantly changing other diode parameters. Such bombardment is thus a useful tool for investigating diode theory. The technique is applied to an expression for the current-voltage characteristic developed for the wide-based p-i-n diode. For high level injection, there are two current density ranges of interest. First, a range where the base voltage is independent of current density and the total junction voltage V varies as exp(qV/2kT) with current. This region corresponds to unity emitter efficiency at each of the junctions. For higher current densities, the emitter efficiency decreases, and the base voltage increases as the square root of the current density. Also, the total junction voltage varies as exp(qV/kT) with current. The theoretical results are then shown to fit the current-voltage characteristics of experimental wide-based silicon p-i-n diodes.