Electronic Applications of Germanium

Abstract

CRYSTAL rectifiers, the essential constituents of which are a metal and semiconductor in contact, are of two types, large-area contact rectifiers, such as copper oxide or selenium rectifiers, and point-contact ones, such as the germanium or silicon type. In both types the semi-conductor, which contains certain impurities, is in the form of a slab making contact on both top and bottom with the metal. For large-area contact rectifiers, rectification is obtained by making the intrinsic rectifications of the two metal-semiconductor contacts of different values, and for the point-contact rectifiers by making the area of one contact, usually the upper one and consisting of a small point at the end of a wire of metal such as tungsten ('cat's whisker'), very much smaller than the area of the other contact, the base electrode.