Point-contact diodes in terms of p-n junction theory

A "formed" n-type germanium point-contact diode is qualitatively reminiscent of an idealized model that comprises an abrupt hemispherical p-n junction, both regions of which may have moderate resistivity, terminated on the inner (p) and outer (n) sides by hemispherical ohmic contacts. The extent to which this model can be justified quantitatively is investigated. Low-injection analyses of the static and small-signal, frequency-dependent properties suggest that the model is capable of predicting the corresponding experimentally-observed behavior. Consideration of space-charge-layer widening with reverse bias allows the computation of breakdown and punch-through voltages, which correspond in magnitude range to the observed peak inverse voltages of formed germanium point contacts. A high-injection analysis of the static forward characteristic indicates approximate agreement between theory and experiment, even for the nonlinear spreading resistance.