Epitaxy generally involves the growth of a coating on a single crystalline substrate, with the coating crystal structure adapting to that of the substrate. Crystalline layers are deposited on wafers in semiconductor technology through metal organic vapour phase epitaxy. The name is derived from metal organic chemical vapour deposition or the synonym metal organic chemical vapour phase epitaxy (MOCVP). The procedure competes with molecular beam epitaxy, which involves the growth of crystals in a high vacuum, while separation of mainly single crystalline layers in the vapour phase occurs at moderate pressures in MOCVD. The technique is used in the production of III-V connection semiconductors such as gallium nitride (GaN), the most important base material today for blue, white and green LED’s. This method also improves the quality of results in single wafer processes. The wafer is held by susceptors during this. These are generally made of graphite coated with silicon carbide. In addition to this, uncoated graphite, quartz glass and silicon carbide are also used. The materials should provide an extremely high degree of purity, temperature and chemical resistance. Use of quartz glass is therefore also limited to fluorine-free processes for this reason.