Triggering phenomena in avalanche diodes

The operation of a small area p-n junction diode above the breakdown voltage is analyzed. A new formulation in terms of ionization probability is used to derive the rate of turn-on of current in such structures. Two differential equations are given which may be used to compute the probability that a carrier swept into or generated within the space-charge region triggers avalanche breakdown. For a 27-V n⁺-p diode biased 1 V above breakdown, this probability is close to 0.5 for an electron entering from the p side, or 0.1 for a hole entering from n side. Experimental measurements are in good agreement with the theoretical predictions.