Switching mechanism in the n-p-n-p silicon controlled rectifier

The OFF state current-voltage characteristics of a two-terminal n-p-n-p silicon controlled rectifier are predicted by considering one-dimensional diffusion of minority carriers in the bulk regions and recombination and generation of carriers in the junction space-charge regions. It is concluded that the temperature dependence of the breakover voltage is strongly dependent on the lifetimes in the space-charge regions of the junctions. Evidence is shown that the carrier lifetime in the space-charge region of an alloyed junction may be less than 10-9seconds even though the lifetime in the bulk is of the order of 10-6seconds. The effect of gate current on the device characteristic and gated turn-off are treated in a very approximate manner.