Diffusion of Impurities in Germanium

A method is described for the study of diffusion of impurities in semiconductors; results are obtained by the observation of the $p-n$ junction formed as the diffusing impurity penetrates the specimen. Studies have been made upon germanium using this technique, and comparisons with the radioactive tracer method have shown the $p-n$ junction method to give valid results. Measurements on indium, gallium, aluminum, arsenic, boron, phosphorus, antimony, and zinc are described. The diffusion coefficients of these elements in germanium range, at 900°C, from ${10}^{-12\mathrm{}}$ ${\mathrm{cm}}^2$/sec to ${10}^{-9\mathrm{}}$ ${\mathrm{cm}}^2$/sec. The activation energy for bulk diffusion in germanium is about 2.5 ev, or 57 000 cal/mole. Applications are given for the study of the $p-n$ junction method to the study of surface and grain-boundary diffusion. The method has also been applied to the study of new elements and their electrical activity in germanium. It is concluded that the rapidity with which results can be obtained by the junction method, and its applicability to elements not conveniently available in radioactive form make it a valuable adjunct to the radioactive tracer method for studying diffusion.