2500-V 600-a gate turn-off thyristor (GTO)

GTO self-turn-off capability provides an advantage over an ordinary thyistor, because of forced commutation circuit removal upon inverter and chopper application, thus substantially reducing equipment size, weight, and mechanical noise. A series of high-power GTO's has been developed, with the present 2500-V-600-A unit as its peak. The most essential design problem for this unit is to establish a principle for increasing maximum gate turn-off current (I
ATO
), while keeping overall thyristor characteristics in reasonable balance. High I
ATO
was attained by decreasing p-base sheet resistance, as well as decreasing n-emitter finger width. Excellent thyristor characteristics were obtained by adopting a low acceptor concentration near the cathode-gate junction. From a device process point of view, introducing a phosphorus redeposition annealing increased carrier lifetime in the p base to a sufficiently high level. This process contributed most strikingly to improving the off-state voltage.