<P> As a wide direct band gap material with resulting resistance to radiation damage, GaAs is an excellent material for outer space electronics and optical windows in high power applications . </P> <P> Because of its wide bandgap, pure GaAs is highly resistive . Combined with a high dielectric constant, this property makes GaAs a very good substrate for Integrated circuits and unlike Si provides natural isolation between devices and circuits . This has made it an ideal material for monolithic microwave integrated circuits, MMICs, where active and essential passive components can readily be produced on a single slice of GaAs . </P> <P> One of the first GaAs microprocessors was developed in the early 1980s by the RCA corporation and was considered for the Star Wars program of the United States Department of Defense . These processors were several times faster and several orders of magnitude more radiation proof than silicon counterparts, but were more expensive . Other GaAs processors were implemented by the supercomputer vendors Cray Computer Corporation, Convex, and Alliant in an attempt to stay ahead of the ever - improving CMOS microprocessor . Cray eventually built one GaAs - based machine in the early 1990s, the Cray - 3, but the effort was not adequately capitalized, and the company filed for bankruptcy in 1995 . </P> <P> Complex layered structures of gallium arsenide in combination with aluminium arsenide (AlAs) or the alloy Al Ga As can be grown using molecular beam epitaxy (MBE) or using metalorganic vapor phase epitaxy (MOVPE). Because GaAs and AlAs have almost the same lattice constant, the layers have very little induced strain, which allows them to be grown almost arbitrarily thick . This allows extremely high performance and high electron mobility HEMT transistors and other quantum well devices . </P>

An advantage of silicon over gallium arsenide is that quizlet