Light-controlled thyristor with anode-base surface firing

Claim 1

A light-controlled thyristor comprising: a pair of main electrodes comprising a cathode electrode and an anode electrode; a semiconductor chip having at least four zones of alternating opposite conductivity types, the first zone contacted by said cathode electrode and the fourth zone contacted by said anode electrode, the first and fourth zones acting as emitter zones, the second zone adjoining the first zone, and the third zone of lowest doping lying between the second and fourth zones, a forward blocking PN-junction being formed between the second and third zones, both the second and the third zones together with the forward blocking PN-junction formed between them extending to a surface of the semiconductor chip on the side with the first zone, and current concentration means comprising at least a part of said third zone extending to the surface forming a curve, said curve at least substantially circumscribing a part of said second zone extending to said surface, the thyristor triggering when the portion of the forward blocking PN-junction reaching the surface is irradiated with light; a highly doped zone of the conductivity type of the first zone provided in the surface of the semiconductor chip, the part of the third zone extending to the surface at least partially circumscribing a part of the highly doped zone whereby irradiation of said forward blocking PN-junction produces a current in said second zone, which current is concentrated by said curve toward said highly doped zone; and, an electrical contact connecting the highly doped zone with the second zone outside the part of the second zone surrounded by the third zone at the surface.