Accelerated power aging with lithium–doped point contact transistors

A point contact transistor with electrical properties similar to those obtained using phosphor-bronze collectors can be made by forming a lithium-doped collector point in a conventional manner. The use of lithium-doped points enables the observation of significant changes in transistor parameters during short periods of moderate power aging. In particular, n-type transistors exhibit a large decrease in reverse current with accompanying loss of alpha. It is proposed that changes in the effective donor concentration in the formed region are responsible for these decreases, in view of the high diffusion rate and low solubility of lithium in germanium. These results emphasize that point contact collector characteristics can change appreciably as a result of surface independent mechanisms.