Wikipedia:WikiProject Chemicals/Chembox validation/VerifiedDataSandbox and Gallium arsenide: Difference between pages

{{Redirect|GaAs||Gaas (disambiguation){{!}}Gaas}}

| verifiedrevid = 476995185

| Name =

| ImageFile =

| ImageFile2 = Gallium Arsenide (GaAs) 2" wafer.jpg

| ImageCaption2=GaAs wafer of (100) orientation

| OtherNames =

| IUPACName =

| SystematicName =

| CASNo = 1303-00-0

| CASNo_Ref = {{cascite|correct|CAS}}

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = 27FC46GA44

| PubChem = 14770

| ChemSpiderID = 14087

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| EINECS = 215-114-8

| UNNumber = 1557

| MeSHName = gallium+arsenide

| RTECS = LW8800000

| SMILES = [Ga]#[As]

| SMILES1 = [Ga+3].[As-3]

| StdInChI = 1S/AsH3.Ga.3H/h1H3;;;;

| StdInChI_Ref = {{stdinchicite|changed|chemspider}}

| StdInChIKey = SHVQQKYXGUBHBI-UHFFFAOYSA-N

| StdInChIKey_Ref = {{stdinchicite|changed|chemspider}}

| Formula = GaAs

| MolarMass = 144.645 g/mol<ref name=crc>Haynes, p. 4.64</ref>

| Appearance = Gray crystals<ref name=crc/>

| Odor = garlic-like when moistened

| Density = 5.3176 g/cm³<ref name=crc/>

| Solubility = insoluble

| SolubleOther = soluble in [[hydrochloric acid|HCl]] <br> insoluble in [[ethanol]], [[methanol]], [[acetone]]

| MeltingPtC = 1238

| MeltingPt_ref =<ref name=crc/>

| BandGap = 1.424 eV (at 300 K)<ref name="Blakemore1982">Blakemore, J. S. "Semiconducting and other major properties of gallium arsenide", Journal of Applied Physics, (1982) vol 53 Nr 10 pages R123-R181</ref>

| ElectronMobility = 9000 cm²/(V·s) (at 300 K)<ref name=crc4>Haynes, p. 12.90</ref>

| ThermalConductivity = 0.56 W/(cm·K) (at 300 K)<ref name=crc2/>

| RefractIndex = 3.3<ref name=crc3/>

| MagSus = -16.2{{e|-6}} cgs<ref name=crc3>Haynes, p. 12.86</ref>

| Structure_ref =<ref name=crc2>Haynes, p. 12.81</ref>

| MolShape = Linear

| CrystalStruct = [[Zincblende (crystal structure)|Zinc blende]]

| SpaceGroup = ''T''²_d-''F''-4''3m''

| LattConst_a = 565.315 pm

| Coordination = Tetrahedral

| Section4 =

| Section5 =

| Section6 =

| GHSPictograms = {{GHS health hazard}}

| GHSSignalWord = '''DANGER'''

| HPhrases = {{H-phrases|350|372|360F}}

| PPhrases = {{P-phrases|261|273|301+310|311|501}}

| ExternalSDS = [http://www.wafertech.co.uk/galliumarsenide.htm External MSDS]

| NFPA-F = 0

| NFPA-H = 3

| NFPA-R = 0

| NFPA-S =

|Section8={{Chembox Related

| OtherAnions = [[Gallium nitride]]<br />[[Gallium phosphide]]<br />[[Gallium antimonide]]

| OtherCations =

}}

'''[[Gallium]] [[arsenide]]''' ('''GaAs''') is a [[III-V]] [[direct band gap]] [[semiconductor]] with a [[Zincblende (crystal structure)|zinc blende]] crystal structure.

Gallium arsenide is used in the manufacture of devices such as [[microwave]] frequency [[integrated circuit]]s, [[monolithic microwave integrated circuit]]s, [[infrared]] [[light-emitting diode]]s, [[laser diode]]s, [[solar cells]] and optical windows.<ref name = "Moss"/>

GaAs is often used as a substrate material for the epitaxial growth of other III-V semiconductors, including [[indium gallium arsenide]], [[aluminum gallium arsenide]] and others.

==Preparation and chemistry==

In the compound, gallium has a +3 [[oxidation state]]. Gallium arsenide [[single crystal]]s can be prepared by three industrial processes:<ref name = "Moss">{{cite book|author1=Moss, S. J. |author2=Ledwith, A. | title = The Chemistry of the Semiconductor Industry| publisher = Springer| year = 1987| isbn = 978-0-216-92005-7}}</ref>

* The vertical gradient freeze (VGF) process.<ref>{{cite book|author1=Scheel, Hans J. |author2=Tsuguo Fukuda. | title = Crystal Growth Technology| publisher = Wiley| year = 2003| isbn = 978-0471490593}}</ref>

* Crystal growth using a horizontal zone furnace in the [[Bridgman-Stockbarger technique]], in which gallium and arsenic vapors react, and free molecules deposit on a seed crystal at the cooler end of the furnace.

* Liquid encapsulated [[Czochralski process|Czochralski]] (LEC) growth is used for producing high-purity single crystals that can exhibit semi-insulating characteristics (see below). Most GaAs wafers are produced using this process.

Alternative methods for producing films of GaAs include:<ref name = "Moss"/><ref>{{cite book|author1=Smart, Lesley |author2=Moore, Elaine A. | title = Solid State Chemistry: An Introduction| publisher = CRC Press| year = 2005| isbn = 978-0-7487-7516-3}}</ref>

* [[Chemical vapor deposition|VPE]] reaction of gaseous gallium metal and [[arsenic trichloride]]: 2 Ga + 2 {{chem|AsCl|3}} → 2 GaAs + 3 {{chem|Cl|2}}

* [[MOCVD]] reaction of [[trimethylgallium]] and [[arsine]]: {{chem|Ga(CH|3|)|3}} + {{chem|AsH|3}} → GaAs + 3 {{chem|CH|4}}

* [[Molecular beam epitaxy]] (MBE) of [[gallium]] and [[arsenic]]: 4 Ga + {{chem|As|4}} → 4 GaAs or 2 Ga + {{chem|As|2}} → 2 GaAs

Oxidation of GaAs occurs in air, degrading performance of the semiconductor. The surface can be passivated by depositing a cubic [[gallium(II) sulfide]] layer using a tert-butyl gallium sulfide compound such as ({{chem|^t|BuGaS)|7}}.<ref>"Chemical vapor deposition from single organometallic precursors" A. R. Barron, M. B. Power, A. N. MacInnes, A. F.Hepp, P. P. Jenkins {{US patent|5300320}} (1994)</ref>

===Semi-insulating crystals===

In the presence of excess arsenic, GaAs [[Boule (crystal)|boules]] grow with [[crystallographic defect]]s; specifically, arsenic antisite defects (an arsenic atom at a gallium atom site within the crystal lattice). The electronic properties of these defects (interacting with others) cause the [[Fermi level]] to be [[Fermi level pinning|pinned]] to near the center of the band gap, so that this GaAs crystal has very low concentration of electrons and holes. This low carrier concentration is similar to an intrinsic (perfectly undoped) crystal, but much easier to achieve in practice. These crystals are called "semi-insulating", reflecting their high resistivity of 10⁷–10⁹ Ω·cm (which is quite high for a semiconductor, but still much lower than a true insulator like glass).<ref name=DD-2012>McCluskey, Matthew D. and Haller, Eugene E. (2012) ''Dopants and Defects in Semiconductors'', pp. 41 and 66, {{ISBN|978-1439831526}}</ref>

===Etching===

Wet etching of GaAs industrially uses an oxidizing agent such as [[hydrogen peroxide]] or [[bromine]] water,<ref>{{cite book|author1=Brozel, M. R. |author2=Stillman, G. E. | title = Properties of Gallium Arsenide| publisher = IEEE Inspec| year = 1996| isbn = 978-0-85296-885-7}}</ref> and the same strategy has been described in a patent relating to processing scrap components containing GaAs where the {{chem|Ga||3+}} is complexed with a [[hydroxamic acid]] ("HA"), for example:<ref>"Oxidative dissolution of gallium arsenide and separation of gallium from arsenic" J. P. Coleman and B. F. Monzyk {{US patent|4759917}} (1988)</ref>

:GaAs + {{chem|H|2|O|2}} + "HA" → "GaA" complex + {{chem|H|3|AsO|4}} + 4 {{chem|H|2|O}}

This reaction produces [[arsenic acid]].<ref>{{cite journal |last1=Lova |first1=Paola |last2=Robbiano |first2=Valentina |last3=Cacialli |first3=Franco |last4=Comoretto |first4=Davide |last5=Soci |first5=Cesare |title=Black GaAs by Metal-Assisted Chemical Etching |journal=ACS Applied Materials & Interfaces |date=3 October 2018 |volume=10 |issue=39 |pages=33434–33440 |doi=10.1021/acsami.8b10370 |pmid=30191706 |s2cid=206490133 |issn=1944-8244|url=https://discovery.ucl.ac.uk/id/eprint/10059695/ }}</ref>

==Electronics==

===GaAs digital logic===

GaAs can be used for various transistor types:<ref name=Fisher1995>{{cite book

| title = Gallium Arsenide IC Applications Handbook

|author1=Dennis Fisher |author2=I. J. Bahl | publisher = Elsevier

| year = 1995

| isbn = 978-0-12-257735-2

| page = 61

| url = https://books.google.com/books?id=KSKJ56kvcSYC&q=source-coupled-fet-logic&pg=PA61

| volume = 1

}} 'Clear search' to see pages</ref>

* [[Metal–semiconductor field-effect transistor]] (MESFET)

* [[High-electron-mobility transistor]] (HEMT)

* [[Junction field-effect transistor]] (JFET)

* [[Heterojunction bipolar transistor]] (HBT)

* [[Metal–oxide–semiconductor field-effect transistor]] (MOSFET)<ref>{{cite book |last1=Ye |first1=Peide D. |last2=Xuan |first2=Yi |last3=Wu |first3=Yanqing |last4=Xu |first4=Min |chapter=Atomic-Layer Deposited High-k/III-V Metal-Oxide-Semiconductor Devices and Correlated Empirical Model |editor-last1=Oktyabrsky |editor-first1=Serge |editor-last2=Ye |editor-first2=Peide |title=Fundamentals of III-V Semiconductor MOSFETs |date=2010 |publisher=[[Springer Science & Business Media]] |pages=173–194 |doi=10.1007/978-1-4419-1547-4_7 |isbn=978-1-4419-1547-4 |chapter-url=https://books.google.com/books?id=sk2SrZH3xEcC&pg=PA173}}</ref>

The HBT can be used in [[integrated injection logic]] (I²L).

The earliest GaAs logic gate used [[Buffered FET Logic]] (BFL).<ref name=Fisher1995/>

From {{circa|1975}} to 1995 the main logic families used were:<ref name=Fisher1995/>

* [[Source-coupled FET logic]] (SCFL) fastest and most complex, (used by TriQuint & Vitesse)

* [[Capacitor–diode FET logic]] (CDFL) (used by Cray for [[Cray-3]])

* [[Direct-coupled FET logic]] (DCFL) simplest and lowest power (used by Vitesse for VLSI gate arrays)

===Comparison with silicon for electronics===

====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.{{citation needed|date=December 2022}} 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.{{citation needed|date=September 2023}}

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|page=[https://archive.org/details/processorarchite0000silc/page/34 34]|url=https://archive.org/details/processorarchite0000silc|url-access=registration|title=Processor architecture: from dataflow to superscalar and beyond|author1=Šilc, Von Jurij |author2=Robič, Borut |author3=Ungerer, Theo |publisher=Springer|year=1999|isbn=978-3-540-64798-0}}</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_xGa_1−xAs]] 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|url=https://arstechnica.com/information-technology/2016/06/cheaper-better-faster-stronger-ars-meets-the-latest-military-bred-chip/|title=A reprieve for Moore's Law: milspec chip writes computing's next chapter|website=Ars Technica|access-date=2016-06-14|date=2016-06-09}}</ref>

====Silicon advantages====

Silicon has three major advantages over GaAs for integrated circuit manufacture. First, silicon is abundant and cheap to process in the form of [[silicate]] minerals. The [[economies of scale]] available to the silicon industry has also hindered the adoption of GaAs.{{citation needed|date=September 2023}}

In addition, a Si crystal has a very stable structure and can be grown to very large diameter [[boule (crystal)|boule]]s and processed with very good yields. It is also a fairly good thermal conductor, thus enabling very dense packing of transistors that need to get rid of their heat of operation, all very desirable for design and manufacturing of very large [[Integrated circuit|IC]]s. Such good mechanical characteristics also make it a suitable material for the rapidly developing field of [[nanoelectronics]]. Naturally, a GaAs surface cannot withstand the high temperatures needed for diffusion; however a viable and actively pursued alternative as of the 1980s was ion implantation.<ref name="Morgan&Board">{{cite book|last1=Morgan|first1=D. V.|last2=Board|first2=K.|title=An Introduction To Semiconductor Microtechnology|date=1991|publisher=John Wiley & Sons|location=Chichester, West Sussex, England|isbn=978-0471924784|page=137|edition=2nd}}</ref>

The second major advantage of Si is the existence of a native oxide ([[silicon dioxide]], SiO₂), which is used as an [[Insulator (electricity)|insulator]]. Silicon dioxide can be incorporated onto silicon circuits easily, and such layers are adherent to the underlying silicon. SiO₂ is not only a good insulator (with a [[band gap]] of 8.9 [[electron volt|eV]]), but the Si-SiO₂ interface can be easily engineered to have excellent electrical properties, most importantly low density of interface states. GaAs does not have a native oxide, does not easily support a stable adherent insulating layer, and does not possess the dielectric strength or surface passivating qualities of the Si-SiO₂.<ref name="Morgan&Board" />

[[Aluminum oxide]] (Al₂O₃) has been extensively studied as a possible gate oxide for GaAs (as well as [[indium gallium arsenide|InGaAs]]).

The third advantage of silicon is that it possesses a higher [[Electron hole|hole]] mobility compared to GaAs (500 versus 400&nbsp;cm²V⁻¹s⁻¹).<ref>Sze, S. M. (1985). ''Semiconductor Devices Physics and Technology''. John Wiley & Sons. Appendix G. {{ISBN|0-471-87424-8}}</ref> This high mobility allows the fabrication of higher-speed P-channel [[field-effect transistor]]s, which are required for [[CMOS]] logic. Because they lack a fast CMOS structure, GaAs circuits must use logic styles which have much higher power consumption; this has made GaAs logic circuits unable to compete with silicon logic circuits.

For manufacturing solar cells, silicon has relatively low [[Molar absorptivity|absorptivity]] for sunlight, meaning about 100 micrometers of Si is needed to absorb most sunlight. Such a layer is relatively robust and easy to handle. In contrast, the absorptivity of GaAs is so high that only a few micrometers of thickness are needed to absorb all of the light. Consequently, GaAs thin films must be supported on a substrate material.<ref name=adv>[https://web.archive.org/web/20100211014421/http://www.eere.energy.gov/solar/tf_single_crystalline.html Single-Crystalline Thin Film]. US Department of Energy</ref>

Silicon is a pure element, avoiding the problems of stoichiometric imbalance and thermal unmixing of GaAs.<ref>{{cite book |last1=Cabrera |first1=Rowan |title=Electronic Devices and Circuits |date=2019 |publisher=EDTECH |isbn=9781839473838 |page=35 |url=https://books.google.com/books?id=EeTEDwAAQBAJ&dq=Silicon+is+a+pure+element,+avoiding+the+problems+of+stoichiometric+imbalance+and+thermal+unmixing+of+GaAs&pg=PA35 |access-date=20 January 2022}}</ref>

Silicon has a nearly perfect lattice; impurity density is very low and allows very small structures to be built (down to [[5 nm process|5&nbsp;nm]] in commercial production as of 2020<ref>{{Cite web|last=Cutress|first=Dr Ian|title='Better Yield on 5nm than 7nm': TSMC Update on Defect Rates for N5|url=https://www.anandtech.com/show/16028/better-yield-on-5nm-than-7nm-tsmc-update-on-defect-rates-for-n5|access-date=2020-08-28|website=www.anandtech.com}}</ref>). In contrast, GaAs has a very high impurity density,<ref>{{cite book |last1=Schlesinger |first1=T.E. |title=Encyclopedia of Materials: Science and Technology |date=2001 |publisher=Elsevier |isbn=9780080431529 |pages=3431–3435 |url=https://doi.org/10.1016/B0-08-043152-6/00612-4 |access-date=27 January 2021 |chapter=Gallium Arsenide|doi=10.1016/B0-08-043152-6/00612-4 }}</ref> which makes it difficult to build integrated circuits with small structures, so the 500&nbsp;nm process is a common process for GaAs.{{Citation needed|date=May 2016}}

Silicon has about three times the thermal conductivity of GaAs, with less risk of local overheating in high power devices.<ref name=at-2016-radar/>

==Other applications==

[[File:MidSTAR-1.jpg|thumb|upright=0.67|[[Multijunction photovoltaic cell|Triple-junction]] GaAs cells covering [[MidSTAR-1]]]]

===Transistor uses===

Gallium arsenide (GaAs) transistors are used in the RF power amplifiers for cell phones and wireless communicating.<ref>{{cite news |date=15 December 2010 |url=https://seekingalpha.com/article/242049-its-a-gaas-critical-component-for-cell-phone-circuits-grows-in-2010|title=It's a GaAS: Critical Component for Cell Phone Circuits Grows in 2010|website=Seeking Alpha }}</ref>

===Solar cells and detectors===

Gallium arsenide is an important semiconductor material for high-cost, high-efficiency [[solar cell]]s and is used for single-crystalline [[thin-film solar cell]]s and for [[multi-junction solar cells]].<ref>{{cite journal |last1=Yin |first1=Jun |last2=Migas |first2=Dmitri B. |last3=Panahandeh-Fard |first3=Majid |last4=Chen |first4=Shi |last5=Wang |first5=Zilong |last6=Lova |first6=Paola |last7=Soci |first7=Cesare |title=Charge Redistribution at GaAs/P3HT Heterointerfaces with Different Surface Polarity |journal=The Journal of Physical Chemistry Letters |date=3 October 2013 |volume=4 |issue=19 |pages=3303–3309 |doi=10.1021/jz401485t }}</ref>

The first known operational use of GaAs solar cells in space was for the [[Venera 3]] mission, launched in 1965. The GaAs solar cells, manufactured by Kvant, were chosen because of their higher performance in high temperature environments.<ref>{{cite book|isbn=978-3-540-79359-5|doi= 10.1007/978-3-540-79359-5 |author1=Strobl, G.F.X. |author2=LaRoche, G. |author3=Rasch, K.-D. |author4=Hey, G. |chapter=2: From Extraterrestrial to Terrestrial Applications|title=High-Efficient Low-Cost Photovoltaics: Recent Developments|publisher= Springer |year=2009|chapter-url= https://cds.cern.ch/record/1338850 }}</ref> GaAs cells were then used for the [[Lunokhod programme|Lunokhod rovers]] for the same reason.{{citation needed|date=September 2023}}

In 1970, the GaAs heterostructure solar cells were developed by the team led by [[Zhores Alferov]] in the [[USSR]],<ref>Alferov, Zh. I., V. M. Andreev, M. B. Kagan, I. I. Protasov and V. G. Trofim, 1970, ‘‘Solar-energy converters based on p-n Al_xGa_1−xAs-GaAs heterojunctions,’’ ''Fiz. Tekh. Poluprovodn. 4'', 2378 (''Sov. Phys. Semicond. 4'', 2047 (1971))</ref><ref>[https://web.archive.org/web/20090225094509/http://www.im.isu.edu.tw/seminar/2005.11.16.pdf Nanotechnology in energy applications]. im.isu.edu.tw. 16 November 2005 (in Chinese) p. 24</ref><ref>[http://nobelprize.org/nobel_prizes/physics/laureates/2000/alferov-lecture.pdf Nobel Lecture] by [[Zhores Alferov]] at nobelprize.org, p. 6</ref> achieving much higher efficiencies. In the early 1980s, the efficiency of the best GaAs solar cells surpassed that of conventional, [[crystalline silicon]]-based solar cells. In the 1990s, GaAs solar cells took over from silicon as the cell type most commonly used for [[photovoltaic array]]s for satellite applications. Later, dual- and triple-junction solar cells based on GaAs with [[germanium]] and [[indium gallium phosphide]] layers were developed as the basis of a triple-junction solar cell, which held a record efficiency of over 32% and can operate also with light as concentrated as 2,000 suns. This kind of solar cell powered the [[Mars Exploration Rover]]s [[Spirit rover|Spirit]] and [[Opportunity rover|Opportunity]], which explored [[Mars]]' surface. Also many [[Solar car racing|solar car]]s utilize GaAs in solar arrays, as did the Hubble Telescope.<ref>{{Cite web |title=Hubble's Instruments Including Control and Support Systems (Cutaway) |url=https://hubblesite.org/contents/media/images/4521-Image |access-date=2022-10-11 |website=HubbleSite.org |language=en}}</ref>

GaAs-based devices hold the world record for the highest-efficiency single-junction solar cell at 29.1% (as of 2019). This high efficiency is attributed to the extreme high quality GaAs epitaxial growth, surface passivation by the AlGaAs,<ref>{{Cite journal|author=Schnitzer, I. |title=Ultrahigh spontaneous emission quantum efficiency, 99.7 % internally and 72 % externally, from AlGaAs/GaAs/AlGaAs double heterostructures |journal=Applied Physics Letters |volume=62 |issue=2 |year=1993 |page = 131 |doi=10.1063/1.109348| display-authors=1|last2=Yablonovitch|first2=E|last3=Caneau|first3=C|last4=Gmitter|first4=T.J|s2cid=14611939 |bibcode = 1993ApPhL..62..131S }}</ref> and the promotion of photon recycling by the thin film design.<ref>{{Cite journal|author=Wang, X.|title=Design of GaAs Solar Cells Operating Close to the Shockley–Queisser Limit |journal=IEEE Journal of Photovoltaics |volume=3 |issue=2 |year=2013 |page = 737 |doi=10.1109/JPHOTOV.2013.2241594| display-authors=1|last2=Khan|first2=M.R|last3=Gray|first3=J|last4=Alam|first4=M.A.|last5=Lundstrom|first5=M.S|s2cid=36523127 }}</ref> GaAs-based [[photovoltaics]] are also responsible for the highest efficiency (as of 2022) of conversion of light to electricity, as researchers from the [[Fraunhofer Institute for Solar Energy Systems]] achieved a 68.9% efficiency when exposing a GaAs [[thin film]] photovoltaic cell to monochromatic laser light with a wavelength of 858 nanometers.<ref>{{Cite web |title=Record Efficiency of 68.9% for GaAs Thin Film Photovoltaic Cell Under Laser Light - Fraunhofer ISE |url=https://www.ise.fraunhofer.de/en/press-media/press-releases/2021/record-efficiency-68-9-percent-for-gaas-thin-film-photovoltaic-cell.html |access-date=2022-10-11 |website=Fraunhofer Institute for Solar Energy Systems ISE |date=28 June 2021 |language=en}}</ref>

Today, multi-junction GaAs cells have the highest efficiencies of existing photovoltaic cells and trajectories show that this is likely to continue to be the case for the foreseeable future.<ref>{{Citation |last=Yamaguchi |first=Masafumi |title=High-Efficiency GaAs-Based Solar Cells |date=2021-04-14 |url=https://www.intechopen.com/books/post-transition-metals/high-efficiency-gaas-based-solar-cells |work=Post-Transition Metals |editor-last=Muzibur Rahman |editor-first=Mohammed |publisher=IntechOpen |language=en |doi=10.5772/intechopen.94365 |isbn=978-1-83968-260-5 |s2cid=228807831 |access-date=2022-10-11 |editor2-last=Mohammed Asiri |editor2-first=Abdullah |editor3-last=Khan |editor3-first=Anish |editor4-last=Inamuddin|doi-access=free }}</ref> In 2022, [[Rocket Lab]] unveiled a solar cell with 33.3% efficiency<ref>{{Cite web |title=Rocket Lab unveils space solar cell with 33.3% efficiency |url=https://isolarparts.com/ko/blogs/nwes2/rocket-lab-unveils-space-solar-cell-with-33-3-efficiency |access-date=2022-10-12 |website=solarparts |date=10 March 2022 |language=ko}}</ref> based on inverted metamorphic multi-junction (IMM) technology. In IMM, the lattice-matched (same lattice parameters) materials are grown first, followed by mismatched materials. The top cell, GaInP, is grown first and lattice matched to the GaAs substrate, followed by a layer of either GaAs or GaInAs with a minimal mismatch, and the last layer has the greatest lattice mismatch.<ref>{{Cite web |last1=Duda |first1=Anna |last2=Ward |first2=Scott |last3=Young |first3=Michelle |date=February 2012 |title=Inverted Metamorphic Multijunction (IMM) Cell Processing Instructions |url=https://www.nrel.gov/docs/fy12osti/54049.pdf |access-date=October 11, 2022 |website=National Renewable Energy Laboratory}}</ref> After growth, the cell is mounted to a secondary handle and the GaAs substrate is removed. A main advantage of the IMM process is that the inverted growth according to lattice mismatch allows a path to higher cell efficiency.

Complex designs of Al_xGa_1−xAs-GaAs devices using [[quantum well]]s can be sensitive to infrared radiation ([[QWIP]]).

GaAs diodes can be used for the detection of X-rays.<ref>[http://ppewww.physics.gla.ac.uk/preprints/97/05/psd1/psd1.html Glasgow University report on CERN detector]. Ppewww.physics.gla.ac.uk. Retrieved on 2013-10-16.</ref>

==== Future outlook of GaAs solar cells ====

Despite GaAs-based photovoltaics being the clear champions of efficiency for solar cells, they have relatively limited use in today's market. In both world electricity generation and world electricity generating capacity, solar electricity is growing faster than any other source of fuel (wind, hydro, biomass, and so on) for the last decade.<ref>{{Cite journal |last1=Haegel |first1=Nancy |last2=Kurtz |first2=Sarah |date=November 2021 |title=Global Progress Toward Renewable Electricity: Tracking the Role of Solar |journal=IEEE Journal of Photovoltaics |publication-date=20 September 2021 |volume=11 |issue=6 |pages=1335–1342 |doi=10.1109/JPHOTOV.2021.3104149 |s2cid=239038321 |issn=2156-3381 |doi-access=free }}</ref> However, GaAs solar cells have not currently been adopted for widespread solar electricity generation. This is largely due to the cost of GaAs solar cells - in space applications, high performance is required and the corresponding high cost of the existing GaAs technologies is accepted. For example, GaAs-based photovoltaics show the best resistance to gamma radiation and high temperature fluctuations, which are of great importance for spacecraft.<ref>{{Cite journal |last1=Papež |first1=Nikola |last2=Gajdoš |first2=Adam |last3=Dallaev |first3=Rashid |last4=Sobola |first4=Dinara |last5=Sedlák |first5=Petr |last6=Motúz |first6=Rastislav |last7=Nebojsa |first7=Alois |last8=Grmela |first8=Lubomír |date=2020-04-30 |title=Performance analysis of GaAs based solar cells under gamma irradiation |url=https://www.sciencedirect.com/science/article/pii/S0169433220300854 |journal=Applied Surface Science |language=en |volume=510 |pages=145329 |doi=10.1016/j.apsusc.2020.145329 |bibcode=2020ApSS..51045329P |s2cid=213661192 |issn=0169-4332}}</ref> But in comparison to other solar cells, III-V solar cells are two to three orders of magnitude more expensive than other technologies such as silicon-based solar cells.<ref name="Horowitz-2018">{{Cite journal |last1=Horowitz |first1=Kelsey A. |last2=Remo |first2=Timothy W. |last3=Smith |first3=Brittany |last4=Ptak |first4=Aaron J. |date=2018-11-27 |title=A Techno-Economic Analysis and Cost Reduction Roadmap for III-V Solar Cells |doi=10.2172/1484349 |osti=1484349 |s2cid=139380070 |url=http://dx.doi.org/10.2172/1484349}}</ref> The primary sources of this cost are the [[Epitaxy|epitaxial growth]] costs and the substrate the cell is deposited on.

GaAs solar cells are most commonly fabricated utilizing epitaxial growth techniques such as [[Metalorganic vapour-phase epitaxy|metal-organic chemical vapor deposition]] (MOCVD) and [[Hydride vapour phase epitaxy|hydride vapor phase epitaxy]] (HVPE). A significant reduction in costs for these methods would require improvements in tool costs, throughput, material costs, and manufacturing efficiency.<ref name="Horowitz-2018" /> Increasing the deposition rate could reduce costs, but this cost reduction would be limited by the fixed times in other parts of the process such as cooling and heating.<ref name="Horowitz-2018" />

The substrate used to grow these solar cells is usually germanium or gallium arsenide which are notably expensive materials. One of the main pathways to reduce substrate costs is to reuse the substrate. An early method proposed to accomplish this is epitaxial lift-off (ELO),<ref>{{Cite journal |last1=Konagai |first1=Makoto |last2=Sugimoto |first2=Mitsunori |last3=Takahashi |first3=Kiyoshi |date=1978-12-01 |title=High efficiency GaAs thin film solar cells by peeled film technology |url=https://dx.doi.org/10.1016/0022-0248%2878%2990449-9 |journal=Journal of Crystal Growth |language=en |volume=45 |pages=277–280 |doi=10.1016/0022-0248(78)90449-9 |bibcode=1978JCrGr..45..277K |issn=0022-0248|doi-access=free }}</ref> but this method is time-consuming, somewhat dangerous (with its use of [[hydrofluoric acid]]), and requires multiple post-processing steps. However, other methods have been proposed that use phosphide-based materials and hydrochloric acid to achieve ELO with [[surface passivation]] and minimal post-[[Etching (microfabrication)|etching]] residues and allows for direct reuse of the GaAs substrate.<ref>{{Cite journal |last1=Cheng |first1=Cheng-Wei |last2=Shiu |first2=Kuen-Ting |last3=Li |first3=Ning |last4=Han |first4=Shu-Jen |last5=Shi |first5=Leathen |last6=Sadana |first6=Devendra K. |date=2013-03-12 |title=Epitaxial lift-off process for gallium arsenide substrate reuse and flexible electronics |journal=Nature Communications |language=en |volume=4 |issue=1 |pages=1577 |doi=10.1038/ncomms2583 |pmid=23481385 |bibcode=2013NatCo...4.1577C |s2cid=205315999 |issn=2041-1723|doi-access=free }}</ref> There is also preliminary evidence that [[spalling]] could be used to remove the substrate for reuse.<ref>{{Cite book |last1=Metaferia |first1=Wondwosen |last2=Chenenko |first2=Jason |last3=Packard |first3=Corinne E. |last4=Ptak |first4=Aaron J. |last5=Schulte |first5=Kevin L. |title=2021 IEEE 48th Photovoltaic Specialists Conference (PVSC) |chapter=(110)-Oriented GaAs Devices and Spalling as a Platform for Low-Cost III-V Photovoltaics |date=2021-06-20 |chapter-url=https://ieeexplore.ieee.org/document/9518754 |location=Fort Lauderdale, FL, USA |publisher=IEEE |pages=1118–1120 |doi=10.1109/PVSC43889.2021.9518754 |osti=1869274 |isbn=978-1-6654-1922-2|s2cid=237319505 }}</ref> An alternative path to reduce substrate cost is to use cheaper materials, although materials for this application are not currently commercially available or developed.<ref name="Horowitz-2018" />

Yet another consideration to lower GaAs solar cell costs could be [[concentrator photovoltaics]]. Concentrators use lenses or parabolic mirrors to focus light onto a solar cell, and thus a smaller (and therefore less expensive) GaAs solar cell is needed to achieve the same results.<ref>{{Cite journal |last1=Papež |first1=Nikola |last2=Dallaev |first2=Rashid |last3=Ţălu |first3=Ştefan |last4=Kaštyl |first4=Jaroslav |date=2021-06-04 |title=Overview of the Current State of Gallium Arsenide-Based Solar Cells |journal=Materials |language=en |volume=14 |issue=11 |pages=3075 |doi=10.3390/ma14113075 |issn=1996-1944 |pmc=8200097 |pmid=34199850|bibcode=2021Mate...14.3075P |doi-access=free }}</ref> Concentrator systems have the highest efficiency of existing photovoltaics.<ref>{{Cite journal |last1=Philipps |first1=Simon P. |last2=Bett |first2=Andreas W. |last3=Horowitz |first3=Kelsey |last4=Kurtz |first4=Sarah |date=2015-12-01 |title=Current Status of Concentrator Photovoltaic (CPV) Technology |doi=10.2172/1351597 |osti=1351597 |url=http://dx.doi.org/10.2172/1351597|doi-access=free }}</ref>

So, technologies such as concentrator photovoltaics and methods in development to lower epitaxial growth and substrate costs could lead to a reduction in the cost of GaAs solar cells and forge a path for use in terrestrial applications.

===Light-emission devices===

[[File:Bandstruktur GaAs en.svg|thumb|Band structure of GaAs. The direct gap of GaAs results in efficient emission of infrared light at 1.424 eV (~870 nm).]]

GaAs has been used to produce near-infrared laser diodes since 1962.<ref>{{cite journal |last=Hall |first=Robert N. |author-link=Robert N. Hall |author2=Fenner, G. E. |author3=Kingsley, J. D. |author4= Soltys, T. J. |author5=Carlson, R. O. |year=1962 |title=Coherent Light Emission From GaAs Junctions |journal=Physical Review Letters |volume=9 |issue=9 |pages=366–369 |doi=10.1103/PhysRevLett.9.366 |bibcode=1962PhRvL...9..366H|doi-access=free }}</ref> It is often used in alloys with other semiconductor compounds for these applications.

''N''-type GaAs doped with silicon donor atoms (on Ga sites) and boron acceptor atoms (on As sites) responds to ionizing radiation by emitting scintillation photons. At cryogenic temperatures it is among the brightest scintillators known<ref name="Derenzo, S. 2018">Derenzo, S.; Bourret, E.; Hanrahan, S.; Bizarri, G. (2018). "Cryogenic scintillation properties of ''n''-type GaAs for the direct detection of MeV/c2 dark matter". Journal of Applied Physics. 123 (11): 114501. arXiv:1802.09171. Bibcode:2018JAP...123k4501D. doi:10.1063/1.5018343. S2CID 56118568</ref><ref name="Vasiukov, S. 2019">Vasiukov, S.; Chiossi, F.; Braggio, C.; Carugno, G.; Moretti, F.; Bourret, E.; Derenzo, S. (2019). "GaAs as a Bright Cryogenic Scintillator for the Detection of Low-Energy Electron Recoils from MeV/c2 Dark Matter". IEEE Transactions on Nuclear Science. 66 (11): 2333–2337. Bibcode:2019ITNS...66.2333V. doi:10.1109/TNS.2019.2946725. S2CID 208208697</ref><ref name="Derenzo, S. 2021">Derenzo, S.; Bourret, E.; Frank-Rotsch, C.; Hanrahan, S.; Garcia-Sciveres, M. (2021). "How silicon and boron dopants govern the cryogenic scintillation properties of ''n''-type GaAs". Nuclear Instruments and Methods in Physics Research Section A. 989: 164957. arXiv:2012.07550. Bibcode:2021NIMPA.98964957D. doi:10.1016/j.nima.2020.164957. S2CID 229158562</ref> and is a promising candidate for detecting rare electronic excitations from interacting dark matter, due to the following six essential factors:

# Silicon donor electrons in GaAs have a binding energy that is among the lowest of all known ''n''-type semiconductors. Free electrons above {{val|8|e=15}} per cm³ are not “frozen out" and remain delocalized at cryogenic temperatures.<ref>Benzaquen, M.; Walsh, D.; Mazuruk, K. (1987). "Conductivity of ''n''-type GaAs near the Mott transition". Physical Review B. 36 (9): 4748–4753. Bibcode:1987PhRvB..36.4748B. doi:10.1103/PhysRevB.36.4748. PMID 9943488</ref>

# Boron and gallium are group III elements, so boron as an impurity primarily occupies the gallium site. However, a sufficient number occupy the arsenic site and act as acceptors that efficiently trap ionization event holes from the valence band.<ref>Pätzold, O.; Gärtner, G.; Irmer, G. (2002). "Boron Site Distribution in Doped GaAs". Physica Status Solidi B. 232 (2): 314–322. Bibcode:2002PSSBR.232..314P. doi:10.1002/1521-3951(200208)232:2<314::AID-PSSB314>3.0.CO;2-#.</ref>

# After trapping an ionization event hole from the valence band, the boron acceptors can combine radiatively with delocalized donor electrons to produce photons 0.2 eV below the cryogenic band-gap energy (1.52 eV). This is an efficient radiative process that produces scintillation photons that are not absorbed by the GaAs crystal.<ref name="Vasiukov, S. 2019"/><ref name="Derenzo, S. 2021"/>

# There is no afterglow, because metastable radiative centers are quickly annihilated by the delocalized electrons. This is evidenced by the lack of thermally induced luminescence.<ref name="Derenzo, S. 2018"/>

# ''N''-type GaAs has a high refractive index (~3.5) and the narrow-beam absorption coefficient is proportional to the free electron density and typically several per cm.<ref>Spitzer, W. G.; Whelan, J. M. (1959). "Infrared Absorption and Electron Effective Mass in ''n''-type Gallium Arsenide". Physical Review. 114 (1): 59–63. Bibcode:1959PhRv..114...59S. doi:10.1103/PhysRev.114.59</ref><ref>Sturge, M. D. (1962). "Optical Absorption of Gallium Arsenide between 0.6 and 2.75 eV". Physical Review. 127 (3): 768–773. Bibcode:1962PhRv..127..768S. doi:10.1103/PhysRev.127.768</ref><ref>Osamura, Kozo; Murakami, Yotaro (1972). "Free Carrier Absorption in ''n''-GaAs". Japanese Journal of Applied Physics. 11 (3): 365–371. Bibcode:1972JaJAP..11..365O. doi:10.1143/JJAP.11.365. S2CID 120981460</ref> One would expect that almost all of the scintillation photons should be trapped and absorbed in the crystal, but this is not the case. Recent Monte Carlo and Feynman path integral calculations have shown that the high luminosity could be explained if most of the narrow beam absorption is not absolute absorption but a '''''novel''''' type of optical scattering from the conduction electrons with a cross section of about 5 x 10⁻¹⁸ cm² that allows scintillation photons to escape total internal reflection.<ref>{{cite journal | arxiv=2203.15056 | doi=10.1016/j.nima.2022.166803 | title=Monte Carlo calculations of the extraction of scintillation light from cryogenic ''n''-type GaAs | year=2022 | last1=Derenzo | first1=Stephen E. | journal=Nuclear Instruments and Methods in Physics Research Section A | volume=1034 | page=166803 | bibcode=2022NIMPA103466803D | s2cid=247779262 }}</ref><ref>S. E. Derenzo (2023), “Feynman photon path integral calculations of optical reflection, diffraction, and scattering from conduction electrons,” Nuclear Instruments and Methods, vol. A1056, pp. 168679. arXiv2309.09827</ref> This cross section is about 10⁷ times larger than Thomson scattering but comparable to the optical cross section of the conduction electrons in a metal mirror.<ref>M. K. Pogodaeva, S. V. Levchenko, V. P. Drachev, and I. R. Gabitov, 3032, “Dielectric function of six elemental metals,” J. Phys.: Conf. Ser., vol. 1890, pp. 012008.</ref>

# ''N''-type GaAs(Si,B) is commercially grown as 10&nbsp;kg crystal ingots and sliced into thin wafers as substrates for electronic circuits. Boron oxide is used as an encapsulant to prevent the loss of arsenic during crystal growth, but also has the benefit of providing boron acceptors for scintillation.

===Fiber optic temperature measurement===

For this purpose an optical fiber tip of an optical fiber temperature sensor is equipped with a gallium arsenide crystal. Starting at a light wavelength of 850&nbsp;nm GaAs becomes optically translucent. Since the spectral position of the band gap is temperature dependent, it shifts about 0.4&nbsp;nm/K. The measurement device contains a light source and a device for the spectral detection of the band gap. With the changing of the band gap, (0.4&nbsp;nm/K) an algorithm calculates the temperature (all 250 ms).<ref name="cc_galliumsensor">[http://www.optocon.de/en/support/documentation-publications/?no_cache=1&cid=293&did=105&sechash=1439a6e7 A New Fiber Optical Thermometer and Its Application for Process Control in Strong Electric, Magnetic, and Electromagnetic Fields] {{Webarchive|url=https://web.archive.org/web/20141129043955/http://www.optocon.de/en/support/documentation-publications/?no_cache=1&cid=293&did=105&sechash=1439a6e7 |date=2014-11-29 }}. optocon.de (PDF; 2,5&nbsp;MB)</ref>

===Spin-charge converters===

GaAs may have applications in [[spintronics]] as it can be used instead of [[platinum]] in [[spin-charge converter]]s and may be more tunable.<ref>[https://web.archive.org/web/20140905101631/http://www.compoundsemiconductor.net/article/94939-gaas-forms-basis-of-tunable-spintronics.html GaAs forms basis of tunable spintronics]. compoundsemiconductor.net. September 2014</ref>

==Safety==

The environment, health and safety aspects of gallium arsenide sources (such as [[trimethylgallium]] and [[arsine]]) and industrial hygiene monitoring studies of [[metalorganic]] precursors have been reported.<ref>{{cite journal|title=Environment, health and safety issues for sources used in MOVPE growth of compound semiconductors|author1=Shenai-Khatkhate, D V |author2=Goyette, R |author3=DiCarlo, R L |author4=Dripps, G |journal=Journal of Crystal Growth|volume=272|issue=1–4|pages=816–821|year=2004|doi=10.1016/j.jcrysgro.2004.09.007|bibcode=2004JCrGr.272..816S}}</ref> California lists gallium arsenide as a [[carcinogen]],<ref>{{cite web|title = Chemicals Listed Effective August 1, 2008 as Known to the State of California to Cause Cancer or Reproductive Toxicity: gallium arsenide, hexafluoroacetone, nitrous oxide and vinyl cyclohexene dioxide|date = 2008-08-01|publisher = OEHHA|url = http://www.oehha.ca.gov/prop65/prop65_list/080108list.html}}</ref> as do [[International Agency for Research on Cancer|IARC]] and [[European Chemicals Agency|ECA]],<ref name=Bomhard/> and it is considered a known carcinogen in animals.<ref>{{cite web|title = NTP Technical Report On The Toxicology And Carcinogenesis Studies Of Gallium Arsenide (Cas No. 1303-00-0) In F344/N Rats And B6c3f1 Mice (Inhalation Studies)|date = September 2000|publisher = U.S. Department Of Health And Human Services: Public Health Service: National Institutes of Health|url = http://ntp.niehs.nih.gov/ntp/htdocs/lt_rpts/tr492.pdf}}</ref><ref>{{cite web|title = Safety Data Sheet: Gallium Arsenide|date = 2015-02-28|publisher = Sigma-Aldrich|url = http://www.sigmaaldrich.com/MSDS/MSDS/DisplayMSDSPage.do?country=US&language=en&productNumber=329010&brand=ALDRICH&PageToGoToURL=http%3A%2F%2Fwww.sigmaaldrich.com%2Fcatalog%2Fproduct%2Faldrich%2F329010%3Flang%3Den}}</ref> On the other hand, a 2013 review (funded by industry) argued against these classifications, saying that when rats or mice inhale fine GaAs powders (as in previous studies), they get cancer from the resulting lung irritation and inflammation, rather than from a primary carcinogenic effect of the GaAs itself—and that, moreover, fine GaAs powders are unlikely to be created in the production or use of GaAs.<ref name=Bomhard>{{cite journal|title=Evaluation of the carcinogenicity of gallium arsenide|author1=Bomhard, E. M. |author2=Gelbke, H. |author3=Schenk, H. |author4=Williams, G. M. |author5=Cohen, S. M. |journal=Critical Reviews in Toxicology|volume=43|issue=5|pages=436–466|year=2013|doi=10.3109/10408444.2013.792329|pmid=23706044|s2cid=207505903 }}</ref>

==See also==

{{div col|colwidth=22em}}

* [[Aluminium arsenide]]

* [[Aluminium gallium arsenide]]

* [[Arsine]]

* [[Cadmium telluride]]

* [[Gallium antimonide]]

* [[Gallium arsenide phosphide]]

* [[Gallium manganese arsenide]]

* [[Gallium nitride]]

* [[Gallium phosphide]]

* [[Heterostructure emitter bipolar transistor]]

* [[Indium arsenide]]

* [[Indium gallium arsenide]]

* [[Indium phosphide]]

* [[Light-emitting diode]]

* [[MESFET]] (metal–semiconductor field-effect transistor)

* [[MOVPE]]

* [[Multijunction solar cell]]

* [[Photomixing]] to generate THz

* [[Trimethylgallium]]

{{div col end}}

==References==

{{reflist|30em}}

==Cited sources==

* {{cite book | editor= Haynes, William M. | year = 2011 | title = CRC Handbook of Chemistry and Physics | edition = 92nd | publisher = [[CRC Press]] | isbn = 978-1439855119| title-link = CRC Handbook of Chemistry and Physics }}

==External links==

{{Commons category}}

* [https://www.atsdr.cdc.gov/csem/csem.html Case Studies in Environmental Medicine: Arsenic Toxicity]

* [http://www.ioffe.ru/SVA/NSM/Semicond/GaAs/index.html Physical properties of gallium arsenide (Ioffe Institute)]

* [https://web.archive.org/web/20060721233640/http://www.logitech.uk.com/gallium_arsenide.asp Facts and figures on processing gallium arsenide]

{{Gallium compounds}}

{{Arsenic compounds}}

{{Arsenides}}

{{Semiconductor laser}}

{{Authority control}}

[[Category:Arsenides]]

[[Category:Inorganic compounds]]

[[Category:Gallium compounds]]

[[Category:IARC Group 1 carcinogens]]

[[Category:Optoelectronics]]

[[Category:III-V semiconductors]]

[[Category:III-V compounds]]

[[Category:Solar cells]]

[[Category:Light-emitting diode materials]]

[[Category:Zincblende crystal structure]]