ELECTRICAL SUPPRESSION OF AVALANCHE CURRENTS IN SEMICONDUCTOR JUNCTIONS

Avalanche currents in the majority of semiconductor junctions can be suppressed by a 'quenching technique.' Use is made of the finite turn-on delay of the avalanche current after an applied voltage exceeds the breakdown voltage. A periodically varying bias voltage will effectively suppress the avalanche current provided it extinguishes the avalanche during each cycle and has a period short compared to the average turn-on delay. This keeps the average avalanche current at a low level. The allowed amplitude range of the quenching signals is found to increase with the avalanche breakdown voltage of the diodes. Measurements of the average avalanche current versus quenching frequency yield values for the turn-on probability of the avalanche. The turn-on probability increases exponentially for voltages above breakdown until saturation sets in. At even higher overvoltages the turn-on rate increases again so that a discharge starts during each cycle. A properly adjusted quenching voltage will not only suppress microplasmas in diodes which contain microplasmas but will also increase the uniformity of breakdown in diodes without microplasmas. Application of the quenching principle to avalanche photodiodes, especially to those containing microplasmas, can significantly increase the gain of the photocurrent. In typical guard ring diodes with microplasmas, current gain improvements at low frequencies by factors of 10-100 were found. © 1969.