Characteristics of fast gate controlled switches

Gate turn-off np np devices have been fabricated and studied under various load current and gate turn-off current conditions. High-speed gate turn-off has been achieved by a selective and controlled gold diffusion. In gate turn-off of pnpn structures there is a delay time and a fall time associated with the decay of the load current. Both of these times are inversely related to the gate current used in turn-off. The fall time is characterized by two time constants determined by the transit time of minority carriers in the two base regions of the pnpn structure. One of these time constants is usually long (about 20 microseconds) because of the wide base necessary to attain high breakover voltages.