Design considerations for large-current GTOs

The current crowding of a GTO during turn-off operation and the limits to operating without breakdown were investigated by a newly developed measurement method of current distribution and by computer simulation. Design considerations for large-current GTOs were clarified as follows: to increase the maximum turnoff current, current crowding is suppressed by a gate structure optimized for the distribution of a steady on-state current, and the maximum current flowing into a unit GTO is reduced in a safe operating area by optimizing the number of unit GTOs. The characteristics of a 4000-A GTO trial-fabricated under these design considerations are shown to confirm the validity of the design assumptions.<
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