Peter Roggwiller

Properties of a high-power field-controlled thyristor

Field controlled thyristors (FCTh) have been realized by a recessed gate technique. Static and dynamic characteristics are measured and compared to theoretical results. During turn-off a new latching mechanism is observed which is explained in terms of a comprehensive physical model. New advanced cascode and cascade circuits are proposed with reduced on resistance, very high current gain and fast, snubberless switching.

A highly interdigitated GTO power switch with recessed gate structure

A highly interdigitated power GTO has been realized with a new technology based on reactive ion etching. The characteristic feature of the device are 50 µm wide vertically walled cathode fingers 30 µm apart from each other. The gate level is recessed 20 µm. The gate metalization is contacted directly on the recessed p-base having a doping concentration ≤2 ċ 1016cm-3. With an ohmic load the turn off dI/dt is about 250 A/µsec cm2(related to the shorted anode area). Storage and fall time are well below 1 µsec at turn off gains close to one. The critical current crowding effect observed in conventional GTOs does not occur in the presented highly interdigitated structure.