Multiterminal P-N-P-N Switches

A silicon p-n-p-n switch (two or three terminal) whose operation depends in part upon electric field transport of minority carriers is described. In a p-n-p-n structure relying upon an electric field to increase one internal alpha sufficiently to produce switching, the "turn-on" current is related to minority-carrier lifetime (diffusion length) and to the resistivity, area, and base width of the section depending upon field transport. It is shown that at least one base region can be of relatively large dimension. This increases "turn-on" current, "on" impedance, and "turn-off" time, but allows greater freedom in some aspects of device design and fabrication at not a great increase of the characteristics mentioned. In particular, two and three terminal p-n-p-n switches, dependent in part upon field transport, can be designed as signal devices or as power devices. Certain features of three-terminal p-n-p-n operation are discussed and experimental results presented.