Germanium P-N-P-N switches

Transistors having bases from 90 to 220 mils wide, with the base contact placed near the collector, have shown marked current gain increases with current, peaking at values from 0.1 to 0.3. This effect is due to drift of the injected carriers in the base electric field set up by the emitter current. If the base contact is placed near the emitter, only very small values of α are obtained. Germanium p-n-p-n diode and triode switches were made to operate primarily on the base field mechanism. They had one very wide (p-type) and one very narrow (n-type) base. The base contact for the switching triode may be placed either on the wide base but near the narrow base, or on the narrow base. In the latter case, much less current is required to switch the device from the high resistance to the high conductance region. When used as n transistor, the dc grounded base current gain of the p-n-p-n triode passes through unity at the turn-off current. A p-n-p-p+ structure, as a component part of the p-n-p-n triode with base contact on the wide base region, is shown to act as a switching diode in much the same way as the germanium p-n-pm unit. When the base contact is made to a narrow base bar-type transistor structure, overlap onto emitter and collector regions often results in a current gain that increases with current. This effect may also be utilized in making p-n-p-n switches.