Calculation of large-signal transients in avalanche diode oscillators

The evolution in time of hole and electron concentrations is calculated for single and double diffused diodes that are biased into breakdown. Results of such calculations allow a study of efficiency and power output of avalanche oscillators as a function of doping profile, bias, and load conditions. A short movie showing the time evolution of hole and electron concentrations in a representative diode structure will be shown. Given the doping profile and hole and electron concentrations at a particular time, the electric field can be calculated from Poisson´s equation. Carrier concentration gradients and electric field yield particle currents. From particle currents and electric field the carrier generation rate due to impact ionization is obtained. Generation and recombination at Shockley-Read recombination centers is calculated from the carrier concentrations. Net carrier generation rate and divergence of particle currents allow the time derivative of the carrier concentrations, and thus the carrier concentrations a short time later, to be computed, and so on. Electric-field and doping dependence of carrier mobilities are incorporated in the calculations.