The on-state voltage reduction of a light-triggered thyristor was studied from the view-points of reducing the thyristor thickness and using a high-injection, low-lifetime structure. High-injection was achieved by increasing the thickness and concentration of the p emitter. The reduction in thyristor thickness was achieved by using a p- layer punch-through structure in both the p base and p emitter. This structure consists of a shallow, high-concentration p layer and a deep, low-concentration p layer. The depletion layer extends through the low-concentration p layer, and it reaches and is stopped by the high-concentration p layer when a high voltage is applied. This structure reduces the thickness by about 5%. The on-state voltage can be reduced for a 6-kV, 5.5-kA light-triggered thyristor by the p- layer punch-through structure and the thick, high-concentration region of the p emitter.
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