Optically controllable static induction thyristor device

Claim 1

An optically controllable semiconductor device, comprising at least one optically controllable unit for varying the conduction of a controllable current path connected in series between first and second output terminals of said semiconductor device, said optically controllable unit comprising: a negative bias voltage source having first and second terminals, with said first terminal of said negative bias voltage source being at a lower potential than said second terminal of said negative bias voltage source; a resistor having first and second terminals with its second terminal coupled to said first terminal of said negative bias voltage source to form a series connection; a photo sensitive element having first and second terminals and having a conduction path between said first and second terminals which varies in accordance with optical irradiation of said photo sensitive element, said first terminal of said photo sensitive element being connected to said first terminal of said resistor and said second terminal of said photo sensitive element being connected to said second terminal of said negative bias voltage source, the connection point of said first terminals of said photo sensitive element and resistor providing an optically controlled bias voltage; an optical source for irradiating said photo sensitive element; and at least one static induction thyristor, said thyristor including a channel region (12) having a first region of relatively low impurity concentration and having a plurality of channel region portions within said first region, said channel region having first and second major surfaces, anode means comprising at least one highly-doped semiconductor anode region (11) of a first conductivity type formed adjacent said first major surface, cathode means comprising a plurality of highly-doped cathode regions (13) formed adjacent said second major surface and electrically connected to said second terminal of said negative bias voltage source, said anode, cathode and channel regions being disposed relative to one another in a semiconductor body so as to define respective current paths between said anode region and different ones of said cathode regions through respective portions of said first region, said respective current paths comprising said controllable current path, said static induction thyristor further including gate means responsive to said optically controlled bias voltage for generating depletion regions extending into said portions of said first region to control current flow through said current paths, said gate means comprising a plurality of gate portions (14) of said first conductivity type and having an impurity concentration throughout each gate portion of at least 1×10 19 cm -3 , said gate portions being electrically connected to one another and to said first terminals of said photo sensitive element and resistor, said static induction thyristor turning off in response to a reverse bias between said gate portions and said cathode regions when said photosensitive element provides said bias voltage to said gate means upon irradiation of said photosensitive element for quenching said static induction thyristor.