Current-induced field enhancement of lateral transistors

A new field-aided lateral p-n-p transistor structure has been developed for integrated circuits that has performance characteristics (hfeand fT) that significantly exceed those of the conventional lateral p-n-p. Two basic mechanisms improve performance: drift-aided base transport and localized emitter injection. Both result from a lateral electric field that is set up within the n-type epitaxial base region by applying a biasing voltage between two n⁺contacts in this high-resistivity epi layer. These contacts straddle the single stripe p-emitter and p-collector regions so as to establish a lateral voltage drop under the emitter. The polarity and magnitude of this voltage gradient will debias the bottom and remote emitter edges causing emission to occur only as the emitter edge closest to the adjacent collector stripe. The effective base width is thereby reduced and, in addition, the p-type minority carriers are accelerated through the base width by drift action of this field. These field-aiding effects theoretically increase both hfeand fTby an order of magnitude, and this has been verified experimentally.