Computer calculations of avalanche-induced relaxation oscillations in silicon diodes

In a computer study of breakdown in silicon diodes, relaxation oscillations were found to occur. The computer program treats field-dependent ionization coefficients, recombination, field-dependent mobilities, diffusion, and, of course, field distortion due to space charges. The applied voltage Vais impressed across a series resistor R and the sample; the latter is shunted by the capacitance C. Both linear and complementary-error-function doping profiles have been assumed. The breakdown voltage of a 2.5 micron p-n junction was found to vary from about 90 to 100 volts depending largely upon the rate of the applied voltage. The threshold for oscillations is about 90v. Maximum amplitude oscillations occur for V and continue with reduced amplitude well above twice the threshold. The frequency of oscillations varies as and inversely as the total sample and shunt capacitance. The range of frequencies calculated thus far is from 2.7 to 32 GHz. The current and voltage wave forms vary from nearly sinusoidal to nearly saw tooth. Equilibrium voltage excursions of have been obtained. Preliminary evaluation gives a maximum efficiency of about 10% for Ω and F.