In the world of semiconductors, germanium arsenide (GeAs) is one of the most important elements. A semimetal, it is a crystalline and brittle metalloid with some properties like a metal (such as iron or copper) and some like a nonmetal (such as phosphorus, sulfur or oxygen).
The most common use for this element is in transistors, which convert electrical energy into mechanical motion in devices such as motors, watches, and computers. It is also used in a variety of optical equipment, especially fiber optics and infrared optical systems.
It was predicted by Dmitri Mendeleev in 1869 to fill out the gap between silicon and tin on his periodic table, and it was first discovered in 1886 by Clemens Winkler. It is a metallic silvery-white crystalline mineral that occurs in several sulfide ores, including 7CuS*FeS*GeS2; argyrodite, 4Ag2S*GeS2; and renierite (Cu,Ge,Fe,Zn,As)S.
GeAs is produced by extracting and reducing the oxide of the ores with strong hydrochloric acid, then distilling the resulting liquid, purifying the residue by repeated redistillation, and hydrolysis to form the metal in a powdery form, which is then melted at high temperatures for casting into ingots or billets. It is a relatively inexpensive semiconductor material.
The p-type electrical conductivity of GeAs is growing with temperature, similar to the conductivity of other elements of group 14 and 15. It is particularly useful for transistors because it has a small band gap that efficiently responds to infrared light. It can be fabricated in nanowires and is used in quantum dot lasers for photovoltaic applications.