Light-controlled thyristor with anode-base surface firing

Abstract

A thyristor, with at least four zones of alternating opposite conductivity types, in which the first and fourth zones are contacted by the main electrodes and act as emitter zones, the second zone adjoins the first zone, and the third zone of lowest doping lies between the second and fourth zones. Both the second and the third zones together with the forward blocking PN-junction formed between them extend to the surface of the thyristor semiconductor chip on the side with the first zone. The portion of the forward blocking PN-junction reaching the surface can be irradiated with light so as to trigger the thyristor. There is provided in the surface a highly doped zone of the conductivity type of the first zone, which is connected with the second zone by an electrical contact on the surface. The part of the third zone extending to the surface encloses part of the second zone and the highly doped zone. The electrical contact connects the highly doped zone with the part of the second zone lying outside the region of the second zone enclosed by the third zone at the surface.