Controlled turn-on thyristor

A multistage amplifying thyristor comprising:

• a semiconductor body comprising a first emitter layer, a first base layer atop said first emitter layer, a second base layer atop said first base layer, a first stage emitter layer atop said second base layer, and a second stage emitter layer atop said second base layer spaced from said first stage emitter layer in a direction of turn on sequence by a portion of said second base layer, said first stage emitter layer having a first edge at its edge toward said second stage emitter layer;
• a first emitter electrode underlying said first emitter layer and in ohmic contact therewith;
• a first stage emitter electrode in a first part overlying said first stage emitter layer and in a second part, situated toward said second stage emitter layer from said first part and in ohmic contact with said second base layer, said first stage emitter electrode having a first edge on its side toward said second stage emitter layer;
• a second stage emitter electrode in ohmic contact with said second stage emitter layer, said second stage emitter layer having a first edge on its side toward said first emitter layer;
• a current control resistor region constituting a portion of said second base region defined on a first side by a projection of said first edge of said first stage emitter electrode onto said second base and on a second side by a projection of said first edge of said second stage emitter layer onto said second base region;
• said current control resistor region having an unmodulated resistance selected to limit to a safe level the turn-on current in each preceding amplifying thyristor stage and having a resistance value R.sub.G of:
• R.sub.G .gtoreq.0.5V.sub.G.sup.2 .DELTA.t.sub.G /C.sub.h .gamma..sub.G (.DELTA.T.sub.MAX)
• wherein V.sub.G is the maximum rated voltage of the device, .DELTA.t.sub.G is the time during which turn-on current flows through the resistor, C.sub.h is the specific thermal capacity of the semiconductor, .gamma..sub.G is the volume of the semiconductor in which the turn-on current for this resistor flows and .DELTA.T.sub.MAX is the maximum permissible temperature rise in this turn-on volume of the semiconductor;
• said first edge of said first stage emitter electrode extending beyond said first edge of said first stage emitter layer toward second stage emitter layer by a predetermined distance of at least the greater of either one thickness of said semiconductor body or two ambipolar diffusion lengths in said first base layer from at least one of:
• an edge of said first stage emitter layer which is on the side of said first stage emitter layer which is away from said second stage emitter layer;
• a first edge of the location occupied by the turn-on plasma beneath said first stage emitter layer during device turn-on, where said first edge of said turn-on plasma is toward said second stage emitter layer;
• and
• said first edge of said first stage emitter layer.