Light-ignitable thyristor with anode-base duct portion extending on cathode surface between thyristor portions

Claim 1

A light-ignitable thyristor formed of a main thyristor and an auxiliary thyristor integrated with said main thyristor on a common semiconductor wafer for ignition boosting of said main thyristor, said integrated main and auxiliary thyristors each consisting of four zones of opposite conductivity type including a cathode zone facing a cathode side surface, a cathode base zone, a common anode base zone and a common anode zone facing an anode side surface, respectively, wherein the anode base zone reaches up to the cathode side surface in a narrow duct forming a duct PN junction with said cathode base zone on the side of the main thyristor cathode zone exposed to the cathode side surface, and the cathode zone of said auxiliary thyristor is surrounded by a gate zone of the main thyristor and in contact therewith, comprising: said gate zone being of the same conductivity type as said cathode base zone but more heavily doped than the latter; means for concentrating current from said gate zone to said cathode zone to raise the ignition sensitivity of said main thyristor, comprising said narrow duct of said anode base zone having a cathode side surface area formed between the gate zone and the cathode zone of the main thyristor; and said cathode side surface area of said anode base zone duct having a width D selected such that a narrow space charge zone is at least partially maintained around the duct PN junction throughout the ignition of said main thyristor.