Computerized Model for Response of Transistors to a Pulse of Ionizing Radiation

A computer program has been formulated to solve the time-dependent differential equations describing electron and hole concentrations and the electric field in one-dimensional planar semiconductor-device geometry. The usual assumptions of small minority-carrier concentration and requirements for separating devices into neutral and space-charge regions are not required since the depletion layer is a natural result of the computer solution. Problems which have been studied include the relaxation of P-N junction diodes and transistors from an intense short pulse of ionizing radiation. The phenomena observed include an apparent long recovery time of diodes in high-impedance circuits, ambipolar diffusion of electron-hole pairs toward the junction of alloy diodes, and electric-field peaking in the depletion layer of reverse-biased alloy junctions.