Editing Metalloid (section)

===Semiconductors and electronics===
[[File:Semiconductor-1.jpg|thumb|left|[[Semiconductor]]-based electronic components. From left to right: a [[transistor]], an [[integrated circuit]], and an [[LED]]. The elements commonly recognised as metalloids find widespread use in such devices, as elemental or [[compound semiconductor]] constituents ([[silicon|Si]], [[germanium|Ge]] or [[GaAs]], for example) or as [[doping (semiconductor)|doping agents]] ([[boron|B]], [[antimony|Sb]], [[tellurium|Te]], for example).|alt=A small square plastic piece with three parallel wire protrusions on one side; a larger rectangular plastic chip with multiple plastic and metal pin-like legs; and a small red light globe with two long wires coming out of its base.]]

All the elements commonly recognised as metalloids (or their compounds) have been used in the semiconductor or solid-state electronic industries.<ref>[[#Berger1997|Berger 1997, p.&nbsp;91]]; [[#Hampel1968|Hampel 1968, passim]]</ref>

Some properties of boron have limited its use as a semiconductor. It has a high melting point, single [[crystal]]s are relatively hard to obtain, and introducing and retaining controlled impurities is difficult.<ref>[[#Rochow1966|Rochow 1966, p.&nbsp;41]]; [[#Berger1997|Berger 1997, pp.&nbsp;42–43]]</ref>

Silicon is the leading commercial semiconductor; it forms the basis of modern electronics (including standard solar cells)<ref name=Bom>[[#Bomgardner|Bomgardner 2013, p.&nbsp;20]]</ref> and information and communication technologies.<ref>[[#Russell2005|Russell & Lee 2005, p.&nbsp;395]]; [[#Brown2009|Brown et al. 2009, p.&nbsp;489]]</ref> This was despite the study of semiconductors, early in the 20th century, having been regarded as the "physics of dirt" and not deserving of close attention.<ref>[[#Haller 2006|Haller 2006, p.&nbsp;4]]: "The study and understanding of the physics of semiconductors progressed slowly in the 19th and early 20th centuries&nbsp;... Impurities and defects&nbsp;... could not be controlled to the degree necessary to obtain reproducible results. This led influential physicists, including [[Wolfgang Pauli|W. Pauli]] and [[Isidor Isaac Rabi|I. Rabi]], to comment derogatorily on the 'Physics of Dirt'."; [[#Hoddeson2007|Hoddeson 2007, pp.&nbsp;25–34 (29)]]</ref>

Germanium has largely been replaced by silicon in semiconducting devices, being cheaper, more resilient at higher operating temperatures, and easier to work during the microelectronic fabrication process.<ref name=Russell2005401>[[#Russell2005|Russell & Lee 2005, p.&nbsp;401]]; [[#Büchel2003|Büchel, Moretto & Woditsch 2003, p.&nbsp;278]]</ref> Germanium is still a constituent of semiconducting [[silicon-germanium]] "alloys" and these have been growing in use, particularly for wireless communication devices; such alloys exploit the higher carrier mobility of germanium.<ref name=Russell2005401/> The synthesis of gram-scale quantities of semiconducting [[germanane]] was reported in 2013. This consists of one-atom thick sheets of hydrogen-terminated germanium atoms, analogous to [[graphane]]. It conducts electrons more than ten times faster than silicon and five times faster than germanium, and is thought to have potential for optoelectronic and sensing applications.<ref>[[#Bianco2013|Bianco et al. 2013]]</ref> The development of a germanium-wire based anode that more than doubles the capacity of [[lithium-ion battery|lithium-ion batteries]] was reported in 2014.<ref>[[#Limerick|University of Limerick 2014]]; [[#Kennedy|Kennedy et al. 2014]]</ref> In the same year, Lee et al. reported that defect-free crystals of [[graphene]] large enough to have electronic uses could be grown on, and removed from, a germanium substrate.<ref>[[#Lee|Lee et al. 2014]]</ref>

Arsenic and antimony are not semiconductors in their [[standard state#Liquids and solids|standard states]]. Both form [[compound semiconductor|type III-V semiconductors]] (such as GaAs, [[AlSb]] or GaInAsSb) in which the average number of valence electrons per atom is the same as that of [[Group 14]] elements, but they have [[direct band gap]]s. These compounds are preferred for optical applications.<ref>[[#Russell2005|Russell & Lee 2005, pp.&nbsp;421–22, 424]]</ref> Antimony nanocrystals may enable [[lithium-ion batteries]] to be replaced by more powerful [[sodium-ion battery|sodium ion batteries]].<ref>[[#He|He et al. 2014]]</ref>

Tellurium, which is a semiconductor in its standard state, is used mainly as a component in [[list of semiconductor materials|type II/VI]] semiconducting-[[chalcogenide]]s; these have applications in electro-optics and electronics.<ref>[[#Berger1997|Berger 1997, p.&nbsp;91]]</ref> [[Cadmium telluride]] (CdTe) is used in solar modules for its high conversion efficiency, low manufacturing costs, and large [[band gap]] of 1.44 eV, letting it absorb a wide range of wavelengths.<ref name=Bom/> [[Bismuth telluride]] (Bi<sub>2</sub>Te<sub>3</sub>), alloyed with selenium and antimony, is a component of [[thermoelectric materials|thermoelectric devices]] used for refrigeration or portable power generation.<ref>[[#ScienceDaily|ScienceDaily 2012]]</ref>

Five metalloids – boron, silicon, germanium, arsenic, and antimony – can be found in cell phones (along with at least 39 other metals and nonmetals).<ref>[[#Reardon2005|Reardon 2005]]; [[#Meskers|Meskers, Hagelüken & Van Damme 2009, p.&nbsp;1131]]</ref> Tellurium is expected to find such use.<ref>[[#The Economist|The Economist 2012]]</ref> Of the less often recognised metalloids, phosphorus, gallium (in particular) and selenium have semiconductor applications. Phosphorus is used in trace amounts as a [[dopant]] for [[n-type semiconductor]]s.<ref>[[#Whitten2007|Whitten 2007, p.&nbsp;488]]</ref> The commercial use of gallium compounds is dominated by semiconductor applications –  in integrated circuits, cell phones, [[laser diode]]s, [[light-emitting diode]]s, [[photodetector]]s, and [[solar cell]]s.<ref>[[#Jaskula|Jaskula 2013]]</ref> Selenium is used in the production of solar cells<ref>[[#GES|German Energy Society 2008, pp.&nbsp;43–44]]</ref> and in high-energy [[surge protector]]s.<ref>[[#Patel|Patel 2012, p.&nbsp;248]]</ref>

Boron, silicon, germanium, antimony, and tellurium,<ref>[[#Moore2014|Moore 2104]]; [[#Utah|University of Utah 2014]]; [[#Xu|Xu et al. 2014]]</ref> as well as heavier metals and metalloids such as Sm, Hg, Tl, Pb, Bi, and Se,<ref>[[#Yang|Yang et al. 2012, p.&nbsp;614]]</ref> can be found in [[topological insulator]]s. These are alloys<ref>[[#Moore2010|Moore 2010, p.&nbsp;195]]</ref> or compounds which, at ultracold temperatures or room temperature (depending on their composition), are metallic conductors on their surfaces but insulators through their interiors.<ref>[[#Moore2011|Moore 2011]]</ref> [[Cadmium arsenide]] Cd<sub>3</sub>As<sub>2</sub>, at about 1 K, is a Dirac-semimetal – a bulk electronic analogue of graphene – in which electrons travel effectively as massless particles.<ref>[[#Liu|Liu 2014]]</ref> These two classes of material are thought to have potential [[topological quantum computing|quantum computing]] applications.<ref>[[#Bradley|Bradley 2014]]; [[#Utah|University of Utah 2014]]</ref>
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