Breakdown in Silicon

The voltage-current, light multiplication, and small-signal ac impedance characteristics of reverse-biased silicon p-n junctions are studied in the breakdown region. Two types of junctions are considered: a uniform diffused junction, and an alloyed junction specifically designed to contain only one region of localized breakdown (microplasma). The results for the single-microplasma junction are as follows: (i) The voltage-current characteristic, which describes the relations existing during the instant the microplasma is on, consists of a negative-resistance unstable region and a positive-resistance stable region. (ii) The multiplication characteristic indicates that the junction is most sensitive to light in the unstable breakdown region. (iii) The small-signal ac impedance characteristic exhibits an inductive component of current in the unstable breakdown region.The single-microplasma junction V-I characteristic is compared with a previous theoretical prediction which discusses the mechanisms underlying the properties of a microplasma; an explanation of the multiplication and impedance characteristics of the single-microplasma junction in terms of these properties is indicated; and lastly, the behavior of a uniform junction, which contains many microplasmas, is explained in terms of the results obtained with a single-microplasma junction.