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A study of space-charge and avalanche multiplication processes in germanium Barker, Alfred Stanley, Jr.

Abstract

PNP structures have been investigated and the various effects encountered described in terms of fundamental aspects of carrier flow. The capacitance of a reverse biased junction in a pnp structure is found to rise abruptly with increase of its reverse bias past the punch-through voltage. This effect arises from the addition of the capacitance of the second junction by the low resistance connection of the space charge column across the n region. An unusual phenomenon called "induced breakdown" is found to occur in certain grown junction transistors. Here the punch-through effect of the space-charge spreading from one junction causes the other junction to suffer avalanche breakdown. Negative resistance is observed in some pnp diodes. This is shown to be a result of the current dependence of the hole transmission process occuring in the n-type transmission region combined with the multiplication effect in the high field region at the collector junction. Current flow in the thin base diode is of a space-charge limited nature in the n region. It is shown that the field over most of the n region is large enough to cause the hole mobility to decrease many fold from its low field value. The slope resistance of a typical diode tends asymptotically to a constant value which is approximately consistent with the model based on a saturated drift velocity for holes in the n region.

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