Editing Gallium arsenide (section)

====GaAs advantages====
Some electronic properties of gallium arsenide are superior to those of [[silicon]]. It has a higher [[saturation velocity|saturated electron velocity]] and higher [[electron mobility]], allowing gallium arsenide transistors to function at frequencies in excess of 250&nbsp;GHz.<ref name="waferworld">{{Cite web |title=What Are the Applications of Gallium Arsenide Semiconductors? {{!}} Wafer World |url=https://www.waferworld.com/post/what-are-the-applications-of-gallium-arsenide-semiconductors |access-date=2024-09-27 |website=www.waferworld.com |language=en}}</ref> GaAs devices are relatively insensitive to overheating, owing to their wider energy band gap, and they also tend to create less [[noise (physics)|noise]] (disturbance in an electrical signal) in electronic circuits than silicon devices, especially at high frequencies. This is a result of higher carrier mobilities and lower resistive device parasitics. These superior properties are compelling reasons to use GaAs circuitry in [[mobile phone]]s, [[communications satellite|satellite]] communications, microwave point-to-point links and higher frequency [[radar]] systems. It is also used in the manufacture of [[Gunn diode]]s for the generation of [[microwave]]s.{{citation needed|date=September 2023}}

Another advantage of GaAs is that it has a [[direct band gap]], which means that it can be used to absorb and emit light efficiently. Silicon has an [[indirect band gap]] and so is relatively poor at emitting light.{{citation needed|date=September 2023}}

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.<ref name="waferworld" />

Because of its wide band gap, pure GaAs is highly resistive. Combined with a high [[dielectric constant]], this property makes GaAs a very good substrate for [[integrated circuit]]s and unlike Si provides natural isolation between devices and circuits.  This has made it an ideal material for [[monolithic microwave integrated circuit]]s (MMICs), where active and essential passive components can readily be produced on a single slice of GaAs.

One of the first GaAs [[microprocessor]]s was developed in the early 1980s by the [[RCA]] Corporation and was considered for the [[Strategic Defense Initiative|Star Wars program]] of the [[United States Department of Defense]]. These processors were several times faster and several orders of magnitude more [[Radiation hardening|radiation resistant]] than their silicon counterparts, but were more expensive.<ref>{{cite book |author1=Šilc, Von Jurij |url=https://archive.org/details/processorarchite0000silc |title=Processor architecture: from dataflow to superscalar and beyond |author2=Robič, Borut |author3=Ungerer, Theo |publisher=Springer |year=1999 |isbn=978-3-540-64798-0 |page=[https://archive.org/details/processorarchite0000silc/page/34 34] |url-access=registration}}</ref> Other GaAs processors were implemented by the [[supercomputer]] vendors [[Cray]] Computer Corporation, [[Convex Computer|Convex]], and [[Alliant Computer Systems|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.

Complex layered structures of gallium arsenide in combination with [[aluminium arsenide]] (AlAs) or the alloy [[Aluminium gallium arsenide|Al<sub>x</sub>Ga<sub>1−x</sub>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 (chemistry)|strain]], which allows them to be grown almost arbitrarily thick.  This allows extremely high performance and high electron mobility [[High-electron-mobility transistor|HEMT]] transistors and other [[quantum well]] devices.

GaAs is used for monolithic radar power amplifiers (but [[Gallium nitride|GaN]] can be less susceptible to heat damage).<ref name="at-2016-radar">{{Cite web |date=2016-06-09 |title=A reprieve for Moore's Law: milspec chip writes computing's next chapter |author-last1=Gallagher|author-first1=Sean|url=https://arstechnica.com/information-technology/2016/06/cheaper-better-faster-stronger-ars-meets-the-latest-military-bred-chip/ |access-date=2016-06-14 |website=Ars Technica}}</ref>