Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard-brittle, grayish-white metalloid in the carbon group, chemically similar to its group neighbours silicon and tin. Pure Ge is a semiconductor with an appearance similar to elemental silicon. Like silicon, It naturally reacts and forms complexes with oxygen in nature.
It is widely distributed in nature but is too reactive to occur free. Primary minerals include argyrodite (from which it was first isolated), germanite, renierite, and canfieldite, all of them rare; only germanite and renierite have been used as commercial sources for the element. Trace quantities of Ge are found in certain zinc blended, in sulfidic ores of copper and arsenic, and in coals, the latter possibly a consequence of the concentration of the element by plants of the Carboniferous Period in geologic history. Certain present-day plants are known to concentrate Ge. Both zinc-process concentrates and ash and flue dusts from coal-burning installations provide commercial sources of germanium.
Characteristics of Germanium
- It is a brittle, silvery-white, semi-metallic element. This form constitutes an allotrope known as a Ge, which has a metallic luster and a diamond cubic crystal structure, the same as diamond.
- At pressures above 120 kbar, It becomes the allotrope β-germanium with the same structure as β-tin. Like silicon, gallium, bismuth, antimony, and water, It is one of the few substances that expands as it solidifies from the molten state.
- It is a semiconductor. Zone refining techniques have led to the production of crystalline germanium for semiconductors that has an impurity of only one part in 1010, making it one of the purest materials ever obtained.
- Pure Ge suffers from the forming of whiskers by spontaneous screw dislocations. If a whisker grows long enough to touch another part of the assembly or a metallic packaging, it can effectively shunt out a p-n junction. This is one of the primary reasons for the failure of old germanium diodes and transistors.