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108-645: LRDR is a gallium nitride ( GaN )-based, solid-state active electronically scanned array (AESA) early-warning radar that allows for continuous coverage, even when it is undergoing maintenance. The radar consists of individual solid state radar blocks that can be combined to scale up the size of the radar. The multi-purpose GaN device used on the prototype version of the LRDR is from the Japanese electronics company Fujitsu , according to Lockheed Martin. Construction in Alaska for

216-503: A by-product during the processing of the ores of other metals. Its main source material is bauxite , the chief ore of aluminium , but minor amounts are also extracted from sulfidic zinc ores ( sphalerite being the main host mineral). In the past, certain coals were an important source. During the processing of bauxite to alumina in the Bayer process , gallium accumulates in the sodium hydroxide liquor. From this it can be extracted by

324-439: A cut-off frequency of one cycle per second, too low for any practical applications, but an effective application of the available theory. At Bell Labs , William Shockley and A. Holden started investigating solid-state amplifiers in 1938. The first p–n junction in silicon was observed by Russell Ohl about 1941 when a specimen was found to be light-sensitive, with a sharp boundary between p-type impurity at one end and n-type at

432-400: A direct bandgap semiconductor in the 1960s ushered in the most important stage in the applications of gallium. In the late 1960s, the electronics industry started using gallium on a commercial scale to fabricate light emitting diodes, photovoltaics and semiconductors, while the metals industry used it to reduce the melting point of alloys . Gallium does not exist as a free element in

540-628: A passive , protective oxide layer. At higher temperatures, however, it reacts with atmospheric oxygen to form gallium(III) oxide , Ga 2 O 3 . Reducing Ga 2 O 3 with elemental gallium in vacuum at 500 °C to 700 °C yields the dark brown gallium(I) oxide , Ga 2 O . Ga 2 O is a very strong reducing agent , capable of reducing H 2 SO 4 to H 2 S . It disproportionates at 800 °C back to gallium and Ga 2 O 3 . Gallium(III) sulfide , Ga 2 S 3 , has 3 possible crystal modifications. It can be made by

648-716: A phosphor . Gallium also forms sulfides in lower oxidation states, such as gallium(II) sulfide and the green gallium(I) sulfide , the latter of which is produced from the former by heating to 1000 °C under a stream of nitrogen. The other binary chalcogenides, Ga 2 Se 3 and Ga 2 Te 3 , have the zincblende structure. They are all semiconductors but are easily hydrolysed and have limited utility. Gallium reacts with ammonia at 1050 °C to form gallium nitride , GaN. Gallium also forms binary compounds with phosphorus , arsenic , and antimony : gallium phosphide (GaP), gallium arsenide (GaAs), and gallium antimonide (GaSb). These compounds have

756-591: A by-product is defined as that amount which is economically extractable from its host materials per year under current market conditions (i.e. technology and price). Reserves and resources are not relevant for by-products, since they cannot be extracted independently from the main-products. Recent estimates put the supply potential of gallium at a minimum of 2,100 t/yr from bauxite, 85 t/yr from sulfidic zinc ores, and potentially 590 t/yr from coal. These figures are significantly greater than current production (375 t in 2016). Thus, major future increases in

864-513: A common semi-insulator is gallium arsenide . Some materials, such as titanium dioxide , can even be used as insulating materials for some applications, while being treated as wide-gap semiconductors for other applications. The partial filling of the states at the bottom of the conduction band can be understood as adding electrons to that band. The electrons do not stay indefinitely (due to the natural thermal recombination ) but they can move around for some time. The actual concentration of electrons

972-423: A completely full valence band is inert, not conducting any current. If an electron is taken out of the valence band, then the trajectory that the electron would normally have taken is now missing its charge. For the purposes of electric current, this combination of the full valence band, minus the electron, can be converted into a picture of a completely empty band containing a positively charged particle that moves in

1080-499: A complex low-coordinated structure in which each gallium atom is surrounded by 10 others, rather than 11–12 neighbors typical of most liquid metals. The physical properties of gallium are highly anisotropic , i.e. have different values along the three major crystallographic axes a , b , and c (see table), producing a significant difference between the linear (α) and volume thermal expansion coefficients. The properties of gallium are strongly temperature-dependent, particularly near

1188-408: A greater volatility than ZnCl 2 : all of these predictions turned out to be true. Gallium was discovered using spectroscopy by French chemist Paul Emile Lecoq de Boisbaudran in 1875 from its characteristic spectrum (two violet lines) in a sample of sphalerite . Later that year, Lecoq obtained the free metal by electrolysis of the hydroxide in potassium hydroxide solution. He named

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1296-410: A guide to the construction of more capable and reliable devices. Alexander Graham Bell used the light-sensitive property of selenium to transmit sound over a beam of light in 1880. A working solar cell, of low efficiency, was constructed by Charles Fritts in 1883, using a metal plate coated with selenium and a thin layer of gold; the device became commercially useful in photographic light meters in

1404-445: A low-pressure chamber to create plasma . A common etch gas is chlorofluorocarbon , or more commonly known Freon . A high radio-frequency voltage between the cathode and anode is what creates the plasma in the chamber. The silicon wafer is located on the cathode, which causes it to be hit by the positively charged ions that are released from the plasma. The result is silicon that is etched anisotropically . The last process

1512-519: A pair is completed. Such carrier traps are sometimes purposely added to reduce the time needed to reach the steady-state. The conductivity of semiconductors may easily be modified by introducing impurities into their crystal lattice . The process of adding controlled impurities to a semiconductor is known as doping . The amount of impurity, or dopant, added to an intrinsic (pure) semiconductor varies its level of conductivity. Doped semiconductors are referred to as extrinsic . By adding impurity to

1620-437: A person's hands at normal human body temperature of 37.0 °C (98.6 °F). Gallium is predominantly used in electronics . Gallium arsenide , the primary chemical compound of gallium in electronics, is used in microwave circuits, high-speed switching circuits, and infrared circuits. Semiconducting gallium nitride and indium gallium nitride produce blue and violet light-emitting diodes and diode lasers . Gallium

1728-431: A semiconducting material would cause it to leave thermal equilibrium and create a non-equilibrium situation. This introduces electrons and holes to the system, which interact via a process called ambipolar diffusion . Whenever thermal equilibrium is disturbed in a semiconducting material, the number of holes and electrons changes. Such disruptions can occur as a result of a temperature difference or photons , which can enter

1836-426: A semiconductor is doped by Group III elements, they will behave like acceptors creating free holes, known as " p-type " doping. The semiconductor materials used in electronic devices are doped under precise conditions to control the concentration and regions of p- and n-type dopants. A single semiconductor device crystal can have many p- and n-type regions; the p–n junctions between these regions are responsible for

1944-501: A silicon atom in the crystal, a vacant state (an electron "hole") is created, which can move around the lattice and function as a charge carrier. Group V elements have five valence electrons, which allows them to act as a donor; substitution of these atoms for silicon creates an extra free electron. Therefore, a silicon crystal doped with boron creates a p-type semiconductor whereas one doped with phosphorus results in an n-type material. During manufacture , dopants can be diffused into

2052-773: A theory of solid-state physics , which developed greatly in the first half of the 20th century. In 1878 Edwin Herbert Hall demonstrated the deflection of flowing charge carriers by an applied magnetic field, the Hall effect . The discovery of the electron by J.J. Thomson in 1897 prompted theories of electron-based conduction in solids. Karl Baedeker , by observing a Hall effect with the reverse sign to that in metals, theorized that copper iodide had positive charge carriers. Johan Koenigsberger  [ de ] classified solid materials like metals, insulators, and "variable conductors" in 1914 although his student Josef Weiss already introduced

2160-472: A vacuum, though with a different effective mass . Because the electrons behave like an ideal gas, one may also think about conduction in very simplistic terms such as the Drude model , and introduce concepts such as electron mobility . For partial filling at the top of the valence band, it is helpful to introduce the concept of an electron hole . Although the electrons in the valence band are always moving around,

2268-479: A variety of methods. The most recent is the use of ion-exchange resin . Achievable extraction efficiencies critically depend on the original concentration in the feed bauxite. At a typical feed concentration of 50 ppm, about 15% of the contained gallium is extractable. The remainder reports to the red mud and aluminium hydroxide streams. Gallium is removed from the ion-exchange resin in solution. Electrolysis then gives gallium metal. For semiconductor use, it

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2376-567: A variety of proportions. These compounds share with better-known semiconductors the properties of intermediate conductivity and a rapid variation of conductivity with temperature, as well as occasional negative resistance . Such disordered materials lack the rigid crystalline structure of conventional semiconductors such as silicon. They are generally used in thin film structures, which do not require material of higher electronic quality, being relatively insensitive to impurities and radiation damage. Almost all of today's electronic technology involves

2484-415: Is a combination of processes that are used to prepare semiconducting materials for ICs. One process is called thermal oxidation , which forms silicon dioxide on the surface of the silicon . This is used as a gate insulator and field oxide . Other processes are called photomasks and photolithography . This process is what creates the patterns on the circuit in the integrated circuit. Ultraviolet light

2592-424: Is a common starting reagent for the formation of organogallium compounds, such as in carbogallation reactions. Gallium trichloride reacts with lithium cyclopentadienide in diethyl ether to form the trigonal planar gallium cyclopentadienyl complex GaCp 3 . Gallium(I) forms complexes with arene ligands such as hexamethylbenzene . Because this ligand is quite bulky, the structure of the [Ga(η -C 6 Me 6 )]

2700-467: Is a function of the temperature, as the probability of getting enough thermal energy to produce a pair increases with temperature, being approximately exp(− E G / kT ) , where k is the Boltzmann constant , T is the absolute temperature and E G is bandgap. The probability of meeting is increased by carrier traps – impurities or dislocations which can trap an electron or hole and hold it until

2808-489: Is a halogen. They also react with alkyl halides to form carbocations and GaX 4 . When heated to a high temperature, gallium(III) halides react with elemental gallium to form the respective gallium(I) halides. For example, GaCl 3 reacts with Ga to form GaCl : At lower temperatures, the equilibrium shifts toward the left and GaCl disproportionates back to elemental gallium and GaCl 3 . GaCl can also be produced by reacting Ga with HCl at 950 °C;

2916-405: Is also used in semiconductors , as a dopant in semiconductor substrates. The melting point of gallium (29.7646°C, 85.5763°F, 302.9146 K) is used as a temperature reference point. Gallium alloys are used in thermometers as a non-toxic and environmentally friendly alternative to mercury , and can withstand higher temperatures than mercury. A melting point of −19 °C (−2 °F), well below

3024-540: Is also used in the production of artificial gadolinium gallium garnet for jewelry. Gallium is considered a technology-critical element by the United States National Library of Medicine and Frontiers Media . Gallium has no known natural role in biology. Gallium(III) behaves in a similar manner to ferric salts in biological systems and has been used in some medical applications, including pharmaceuticals and radiopharmaceuticals . Elemental gallium

3132-407: Is an ionic compound strongly insoluble in water. However, it dissolves in hydrofluoric acid , in which it forms an adduct with water, GaF 3 ·3H 2 O . Attempting to dehydrate this adduct forms GaF 2 OH· n H 2 O . The adduct reacts with ammonia to form GaF 3 ·3NH 3 , which can then be heated to form anhydrous GaF 3 . Gallium trichloride is formed by

3240-404: Is called diffusion . This is the process that gives the semiconducting material its desired semiconducting properties. It is also known as doping . The process introduces an impure atom to the system, which creates the p–n junction . To get the impure atoms embedded in the silicon wafer, the wafer is first put in a 1,100 degree Celsius chamber. The atoms are injected in and eventually diffuse with

3348-415: Is contained in known reserves of bauxite and zinc ores. Some coal flue dusts contain small quantities of gallium, typically less than 1% by weight. However, these amounts are not extractable without mining of the host materials (see below). Thus, the availability of gallium is fundamentally determined by the rate at which bauxite, zinc ores, and coal are extracted. Gallium is produced exclusively as

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3456-427: Is further purified with zone melting or single-crystal extraction from a melt ( Czochralski process ). Purities of 99.9999% are routinely achieved and commercially available. Its by-product status means that gallium production is constrained by the amount of bauxite, sulfidic zinc ores (and coal) extracted per year. Therefore, its availability needs to be discussed in terms of supply potential. The supply potential of

3564-446: Is in group 13 of the periodic table and is similar to the other metals of the group ( aluminium , indium , and thallium ). Elemental gallium is a relatively soft, silvery metal at standard temperature and pressure . In its liquid state, it becomes silvery white. If enough force is applied, solid gallium may fracture conchoidally . Since its discovery in 1875, gallium has widely been used to make alloys with low melting points. It

3672-410: Is increased by adding a small amount (of the order of 1 in 10 ) of pentavalent ( antimony , phosphorus , or arsenic ) or trivalent ( boron , gallium , indium ) atoms. This process is known as doping, and the resulting semiconductors are known as doped or extrinsic semiconductors . Apart from doping, the conductivity of a semiconductor can be improved by increasing its temperature. This is contrary to

3780-776: Is inert, blocking the passage of other electrons via that state. The energies of these quantum states are critical since a state is partially filled only if its energy is near the Fermi level (see Fermi–Dirac statistics ). High conductivity in material comes from it having many partially filled states and much state delocalization. Metals are good electrical conductors and have many partially filled states with energies near their Fermi level. Insulators , by contrast, have few partially filled states, their Fermi levels sit within band gaps with few energy states to occupy. Importantly, an insulator can be made to conduct by increasing its temperature: heating provides energy to promote some electrons across

3888-605: Is just above room temperature, and is approximately the same as the average summer daytime temperatures in Earth's mid-latitudes. This melting point (mp) is one of the formal temperature reference points in the International Temperature Scale of 1990 (ITS-90) established by the International Bureau of Weights and Measures (BIPM). The triple point of gallium, 302.9166 K (29.7666 °C, 85.5799 °F),

3996-841: Is neither a very good insulator nor a very good conductor. However, one important feature of semiconductors (and some insulators, known as semi-insulators ) is that their conductivity can be increased and controlled by doping with impurities and gating with electric fields. Doping and gating move either the conduction or valence band much closer to the Fermi level and greatly increase the number of partially filled states. Some wider-bandgap semiconductor materials are sometimes referred to as semi-insulators . When undoped, these have electrical conductivity nearer to that of electrical insulators, however they can be doped (making them as useful as semiconductors). Semi-insulators find niche applications in micro-electronics, such as substrates for HEMT . An example of

4104-823: Is not found in nature, but it is easily obtained by smelting . Very pure gallium is a silvery blue metal that fractures conchoidally like glass . Gallium's volume expands by 3.10% when it changes from a liquid to a solid so care must be taken when storing it in containers that may rupture when it changes state. Gallium shares the higher-density liquid state with a short list of other materials that includes water , silicon , germanium , bismuth , and plutonium . Gallium forms alloys with most metals. It readily diffuses into cracks or grain boundaries of some metals such as aluminium, aluminium – zinc alloys and steel , causing extreme loss of strength and ductility called liquid metal embrittlement . The melting point of gallium, at 302.9146 K (29.7646 °C, 85.5763 °F),

4212-399: Is one of the four non-radioactive metals (with caesium , rubidium , and mercury ) that are known to be liquid at, or near, normal room temperature. Of the four, gallium is the only one that is neither highly reactive (as are rubidium and caesium) nor highly toxic (as is mercury) and can, therefore, be used in metal-in-glass high-temperature thermometers . It is also notable for having one of

4320-545: Is that of a half-sandwich . Less bulky ligands such as mesitylene allow two ligands to be attached to the central gallium atom in a bent sandwich structure. Benzene is even less bulky and allows the formation of dimers: an example is [Ga(η -C 6 H 6 ) 2 ] [GaCl 4 ]·3C 6 H 6 . In 1871, the existence of gallium was first predicted by Russian chemist Dmitri Mendeleev , who named it " eka-aluminium " from its position in his periodic table . He also predicted several properties of eka-aluminium that correspond closely to

4428-500: Is typically very dilute, and so (unlike in metals) it is possible to think of the electrons in the conduction band of a semiconductor as a sort of classical ideal gas , where the electrons fly around freely without being subject to the Pauli exclusion principle . In most semiconductors, the conduction bands have a parabolic dispersion relation , and so these electrons respond to forces (electric field, magnetic field, etc.) much as they would in

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4536-463: Is unique among the light isotopes in having only electron capture as a decay mode, as its decay energy is not sufficient to allow positron emission. Gallium-67 and gallium-68 (half-life 67.7 min) are both used in nuclear medicine . Gallium is found primarily in the +3 oxidation state . The +1 oxidation state is also found in some compounds, although it is less common than it is for gallium's heavier congeners indium and thallium . For example,

4644-402: Is used along with a photoresist layer to create a chemical change that generates the patterns for the circuit. The etching is the next process that is required. The part of the silicon that was not covered by the photoresist layer from the previous step can now be etched. The main process typically used today is called plasma etching . Plasma etching usually involves an etch gas pumped in

4752-500: Is used by the US National Institute of Standards and Technology (NIST) in preference to the melting point. The melting point of gallium allows it to melt in the human hand, and then solidify if removed. The liquid metal has a strong tendency to supercool below its melting point / freezing point : Ga nanoparticles can be kept in the liquid state below 90 K. Seeding with a crystal helps to initiate freezing. Gallium

4860-611: The Ticonderoga -class cruiser and Arleigh Burke -class destroyer to beyond the 2040s. In December 2021, the AN/SPY-6 AESA radar from Raytheon was selected to retrofit Flight IIA Arleigh Burke destroyers; the same radar is used on Flight III ships. Gallium Gallium is a chemical element ; it has the symbol Ga and atomic number 31. Discovered by the French chemist Paul-Émile Lecoq de Boisbaudran in 1875, gallium

4968-527: The Annalen der Physik und Chemie in 1835; Rosenschöld's findings were ignored. Simon Sze stated that Braun's research was the earliest systematic study of semiconductor devices. Also in 1874, Arthur Schuster found that a copper oxide layer on wires had rectification properties that ceased when the wires are cleaned. William Grylls Adams and Richard Evans Day observed the photovoltaic effect in selenium in 1876. A unified explanation of these phenomena required

5076-454: The Ga(OH) 4 anion. Gallium hydroxide, which is amphoteric , also dissolves in alkali to form gallate salts. Although earlier work suggested Ga(OH) 6 as another possible gallate anion, it was not found in later work. Gallium reacts with the chalcogens only at relatively high temperatures. At room temperature, gallium metal is not reactive with air and water because it forms

5184-429: The Pauli exclusion principle ). These states are associated with the electronic band structure of the material. Electrical conductivity arises due to the presence of electrons in states that are delocalized (extending through the material), however in order to transport electrons a state must be partially filled , containing an electron only part of the time. If the state is always occupied with an electron, then it

5292-450: The Siege of Leningrad after successful completion. In 1926, Julius Edgar Lilienfeld patented a device resembling a field-effect transistor , but it was not practical. R. Hilsch  [ de ] and R. W. Pohl  [ de ] in 1938 demonstrated a solid-state amplifier using a structure resembling the control grid of a vacuum tube; although the device displayed power gain, it had

5400-445: The band gap , be accompanied by the emission of thermal energy (in the form of phonons ) or radiation (in the form of photons ). In some states, the generation and recombination of electron–hole pairs are in equipoise. The number of electron-hole pairs in the steady state at a given temperature is determined by quantum statistical mechanics . The precise quantum mechanical mechanisms of generation and recombination are governed by

5508-470: The conservation of energy and conservation of momentum . As the probability that electrons and holes meet together is proportional to the product of their numbers, the product is in the steady-state nearly constant at a given temperature, providing that there is no significant electric field (which might "flush" carriers of both types, or move them from neighbor regions containing more of them to meet together) or externally driven pair generation. The product

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5616-406: The crystal structure . When two differently doped regions exist in the same crystal, a semiconductor junction is created. The behavior of charge carriers , which include electrons , ions , and electron holes , at these junctions is the basis of diodes , transistors , and most modern electronics . Some examples of semiconductors are silicon , germanium , gallium arsenide , and elements near

5724-461: The 1930s. Point-contact microwave detector rectifiers made of lead sulfide were used by Jagadish Chandra Bose in 1904; the cat's-whisker detector using natural galena or other materials became a common device in the development of radio . However, it was somewhat unpredictable in operation and required manual adjustment for best performance. In 1906, H.J. Round observed light emission when electric current passed through silicon carbide crystals,

5832-675: The AN/SPY-7(V)1 will be used on the River-class destroyer and the Spanish F-110 frigate . In September 2020, AN/SPY-7(V)1 was chosen by Canada as the primary radar for its future River-class destroyer along with CMS-330 Combat Management System with Aegis Combat System . Lockheed Martin promoted this version of radar as the AN/SPY-1 refurbishment program to the US Navy to extend the lifespan of

5940-498: The Earth's crust, and the few high-content minerals, such as gallite (CuGaS 2 ), are too rare to serve as a primary source. The abundance in the Earth's crust is approximately 16.9  ppm . It is the 34th most abundant element in the crust. This is comparable to the crustal abundances of lead , cobalt , and niobium . Yet unlike these elements, gallium does not form its own ore deposits with concentrations of > 0.1 wt.% in ore. Rather it occurs at trace concentrations similar to

6048-678: The Flight Test Other-26 (FTX-26) was cancelled due to an anomaly with the live ballistic missile target. When operational, the LRDR will be tied into the Ground-Based Midcourse Defense system and the Command and Control, Battle Management and Communications system . The AN/SPY-7(V)1 is the official designation of an LRDR-derivative used with the Aegis Ballistic Missile Defense System . On 30 July 2018,

6156-566: The Japanese government approved a plan to purchase two pairs of AN/SPY-7(V)1 for the Aegis Ashore facility and will be installed in Yamaguchi Prefecture and Akita Prefecture . The first operation is expected to start from 2025, by Japan Ground Self Defense Force . Missile Defense Agency has also decided to use AN/SPY-7(V)1 for the Aegis Ashore to be installed in Hawaii . Derivatives of

6264-505: The LRDR was scheduled to begin in 2019, tentatively at Clear Space Force Station in central Alaska. Each AESA's dimensions are 60 feet high by 60 feet wide; the field of view is 220 degrees. In late February 2021, the Missile Defense Agency said that the radar installation was underway, with Initial Operational Capability to be achieved in 2021. Testing for Full Operational Capability is expected by 2023. In mid-August 2023,

6372-403: The [Ar]3d core. This phenomenon recurs with mercury with its "pseudo-noble-gas" [Xe]4f 5d 6s electron configuration, which is liquid at room temperature. The 3d electrons do not shield the outer electrons very well from the nucleus and hence the first ionisation energy of gallium is greater than that of aluminium. Ga 2 dimers do not persist in the liquid state and liquid gallium exhibits

6480-416: The band gap, inducing partially filled states in both the band of states beneath the band gap ( valence band ) and the band of states above the band gap ( conduction band ). An (intrinsic) semiconductor has a band gap that is smaller than that of an insulator and at room temperature, significant numbers of electrons can be excited to cross the band gap. A pure semiconductor, however, is not very useful, as it

6588-467: The behavior of a metal, in which conductivity decreases with an increase in temperature. The modern understanding of the properties of a semiconductor relies on quantum physics to explain the movement of charge carriers in a crystal lattice . Doping greatly increases the number of charge carriers within the crystal. When a semiconductor is doped by Group V elements, they will behave like donors creating free electrons , known as " n-type " doping. When

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6696-479: The by-product production of gallium will be possible without significant increases in production costs or price. The average price for low-grade gallium was $ 120 per kilogram in 2016 and $ 135–140 per kilogram in 2017. Semiconductor A semiconductor is a material that is between the conductor and insulator in ability to conduct electrical current. In many cases their conducting properties may be altered in useful ways by introducing impurities (" doping ") into

6804-489: The concept of band gaps had been developed. Walter H. Schottky and Nevill Francis Mott developed models of the potential barrier and of the characteristics of a metal–semiconductor junction . By 1938, Boris Davydov had developed a theory of the copper-oxide rectifier, identifying the effect of the p–n junction and the importance of minority carriers and surface states. Agreement between theoretical predictions (based on developing quantum mechanics) and experimental results

6912-855: The construction of light-emitting diodes and fluorescent quantum dots . Semiconductors with high thermal conductivity can be used for heat dissipation and improving thermal management of electronics. They play a crucial role in electric vehicles , high-brightness LEDs and power modules , among other applications. Semiconductors have large thermoelectric power factors making them useful in thermoelectric generators , as well as high thermoelectric figures of merit making them useful in thermoelectric coolers . A large number of elements and compounds have semiconducting properties, including: The most common semiconducting materials are crystalline solids, but amorphous and liquid semiconductors are also known. These include hydrogenated amorphous silicon and mixtures of arsenic , selenium , and tellurium in

7020-425: The crustal value in zinc ores, and at somewhat higher values (~ 50 ppm) in aluminium ores, from both of which it is extracted as a by-product. This lack of independent deposits is due to gallium's geochemical behaviour, showing no strong enrichment in the processes relevant to the formation of most ore deposits. The United States Geological Survey (USGS) estimates that more than 1 million tons of gallium

7128-583: The density of gallium as 4.7 g/cm , the only property that failed to match Mendeleev's predictions; Mendeleev then wrote to him and suggested that he should remeasure the density, and de Boisbaudran then obtained the correct value of 5.9 g/cm , that Mendeleev had predicted exactly. From its discovery in 1875 until the era of semiconductors, the primary uses of gallium were high-temperature thermometrics and metal alloys with unusual properties of stability or ease of melting (some such being liquid at room temperature). The development of gallium arsenide as

7236-453: The electrical properties of materials. The properties of the time-temperature coefficient of resistance, rectification, and light-sensitivity were observed starting in the early 19th century. Thomas Johann Seebeck was the first to notice that semiconductors exhibit special feature such that experiment concerning an Seebeck effect emerged with much stronger result when applying semiconductors, in 1821. In 1833, Michael Faraday reported that

7344-530: The electrons in the conduction band). When ionizing radiation strikes a semiconductor, it may excite an electron out of its energy level and consequently leave a hole. This process is known as electron-hole pair generation . Electron-hole pairs are constantly generated from thermal energy as well, in the absence of any external energy source. Electron-hole pairs are also apt to recombine. Conservation of energy demands that these recombination events, in which an electron loses an amount of energy larger than

7452-526: The element "gallia", from Latin Gallia meaning ' Gaul ', a name for his native land of France. It was later claimed that, in a multilingual pun of a kind favoured by men of science in the 19th century, he had also named gallium after himself: Le coq is French for 'the rooster', and the Latin word for 'rooster' is gallus . In an 1877 article, Lecoq denied this conjecture. Originally, de Boisbaudran determined

7560-486: The exceptions of quartz, graphite, gallium(III) oxide and PTFE ), making it mechanically more difficult to handle even though it is substantially less toxic and requires far fewer precautions than mercury. Gallium painted onto glass is a brilliant mirror. For this reason as well as the metal contamination and freezing-expansion problems, samples of gallium metal are usually supplied in polyethylene packets within other containers. Gallium does not crystallize in any of

7668-474: The excess or shortage of electrons, respectively. A balanced number of electrons would cause a current to flow throughout the material. Homojunctions occur when two differently doped semiconducting materials are joined. For example, a configuration could consist of p-doped and n-doped germanium . This results in an exchange of electrons and holes between the differently doped semiconducting materials. The n-doped germanium would have an excess of electrons, and

7776-514: The fast response of crystal detectors. Considerable research and development of silicon materials occurred during the war to develop detectors of consistent quality. Detector and power rectifiers could not amplify a signal. Many efforts were made to develop a solid-state amplifier and were successful in developing a device called the point contact transistor which could amplify 20 dB or more. In 1922, Oleg Losev developed two-terminal, negative resistance amplifiers for radio, but he died in

7884-470: The freezing point of water, is claimed for the alloy galinstan (62–⁠95% gallium, 5–⁠22% indium , and 0–⁠16% tin by weight), but that may be the freezing point with the effect of supercooling . Gallium does not occur as a free element in nature, but rather as gallium(III) compounds in trace amounts in zinc ores (such as sphalerite ) and in bauxite . Elemental gallium is a liquid at temperatures greater than 29.76 °C (85.57 °F), and will melt in

7992-419: The hydrated gallium ion, [Ga(H 2 O) 6 ] . Gallium(III) hydroxide , Ga(OH) 3 , may be precipitated from gallium(III) solutions by adding ammonia . Dehydrating Ga(OH) 3 at 100 °C produces gallium oxide hydroxide, GaO(OH). Alkaline hydroxide solutions dissolve gallium, forming gallate salts (not to be confused with identically named gallic acid salts) containing

8100-495: The invention of the transistor in 1947 and the integrated circuit in 1958. Semiconductors in their natural state are poor conductors because a current requires the flow of electrons, and semiconductors have their valence bands filled, preventing the entire flow of new electrons. Several developed techniques allow semiconducting materials to behave like conducting materials, such as doping or gating . These modifications have two outcomes: n-type and p-type . These refer to

8208-404: The largest liquid ranges for a metal, and for having (unlike mercury) a low vapor pressure at high temperatures. Gallium's boiling point, 2676 K, is nearly nine times higher than its melting point on the absolute scale , the greatest ratio between melting point and boiling point of any element. Unlike mercury, liquid gallium metal wets glass and skin, along with most other materials (with

8316-431: The longest-lived (half-life 3.261 days). Isotopes lighter than gallium-69 usually decay through beta plus decay (positron emission) or electron capture to isotopes of zinc , while isotopes heavier than gallium-71 decay through beta minus decay (electron emission), possibly with delayed neutron emission , to isotopes of germanium . Gallium-70 can decay through both beta minus decay and electron capture. Gallium-67

8424-543: The material's majority carrier . The opposite carrier is called the minority carrier , which exists due to thermal excitation at a much lower concentration compared to the majority carrier. For example, the pure semiconductor silicon has four valence electrons that bond each silicon atom to its neighbors. In silicon, the most common dopants are group III and group V elements. Group III elements all contain three valence electrons, causing them to function as acceptors when used to dope silicon. When an acceptor atom replaces

8532-452: The melting point. For example, the coefficient of thermal expansion increases by several hundred percent upon melting. Gallium has 30 known isotopes, ranging in mass number from 60 to 89. Only two isotopes are stable and occur naturally, gallium-69 and gallium-71. Gallium-69 is more abundant: it makes up about 60.1% of natural gallium, while gallium-71 makes up the remaining 39.9%. All the other isotopes are radioactive, with gallium-67 being

8640-509: The order Al > Ga > In and as a result organogallium compounds do not form bridged dimers as organoaluminium compounds do. Organogallium compounds are also less reactive than organoaluminium compounds. They do form stable peroxides. These alkylgalliums are liquids at room temperature, having low melting points, and are quite mobile and flammable. Triphenylgallium is monomeric in solution, but its crystals form chain structures due to weak intermolecluar Ga···C interactions. Gallium trichloride

8748-588: The other, showing variable resistance, and having sensitivity to light or heat. Because the electrical properties of a semiconductor material can be modified by doping and by the application of electrical fields or light, devices made from semiconductors can be used for amplification, switching, and energy conversion . The term semiconductor is also used to describe materials used in high capacity, medium- to high-voltage cables as part of their insulation, and these materials are often plastic XLPE ( Cross-linked polyethylene ) with carbon black. The conductivity of silicon

8856-449: The other. A slice cut from the specimen at the p–n boundary developed a voltage when exposed to light. The first working transistor was a point-contact transistor invented by John Bardeen , Walter Houser Brattain , and William Shockley at Bell Labs in 1947. Shockley had earlier theorized a field-effect amplifier made from germanium and silicon, but he failed to build such a working device, before eventually using germanium to invent

8964-417: The p-doped germanium would have an excess of holes. The transfer occurs until an equilibrium is reached by a process called recombination , which causes the migrating electrons from the n-type to come in contact with the migrating holes from the p-type. The result of this process is a narrow strip of immobile ions , which causes an electric field across the junction. A difference in electric potential on

9072-508: The point-contact transistor. In France, during the war, Herbert Mataré had observed amplification between adjacent point contacts on a germanium base. After the war, Mataré's group announced their " Transistron " amplifier only shortly after Bell Labs announced the " transistor ". In 1954, physical chemist Morris Tanenbaum fabricated the first silicon junction transistor at Bell Labs . However, early junction transistors were relatively bulky devices that were difficult to manufacture on

9180-708: The presence of dimethyl ether as solvent, GaH 3 polymerizes to (GaH 3 ) n . If no solvent is used, the dimer Ga 2 H 6 ( digallane ) is formed as a gas. Its structure is similar to diborane , having two hydrogen atoms bridging the two gallium centers, unlike α- AlH 3 in which aluminium has a coordination number of 6. Gallane is unstable above −10 °C, decomposing to elemental gallium and hydrogen . Organogallium compounds are of similar reactivity to organoindium compounds, less reactive than organoaluminium compounds, but more reactive than organothallium compounds. Alkylgalliums are monomeric. Lewis acidity decreases in

9288-524: The principle behind the light-emitting diode . Oleg Losev observed similar light emission in 1922, but at the time the effect had no practical use. Power rectifiers, using copper oxide and selenium, were developed in the 1920s and became commercially important as an alternative to vacuum tube rectifiers. The first semiconductor devices used galena , including German physicist Ferdinand Braun's crystal detector in 1874 and Indian physicist Jagadish Chandra Bose's radio crystal detector in 1901. In

9396-564: The product can be condensed as a red solid. Gallium(I) compounds can be stabilized by forming adducts with Lewis acids. For example: The so-called "gallium(II) halides", GaX 2 , are actually adducts of gallium(I) halides with the respective gallium(III) halides, having the structure Ga [GaX 4 ] . For example: Like aluminium , gallium also forms a hydride , GaH 3 , known as gallane , which may be produced by reacting lithium gallanate ( LiGaH 4 ) with gallium(III) chloride at −30 °C: In

9504-574: The pure semiconductors, the electrical conductivity may be varied by factors of thousands or millions. A 1 cm specimen of a metal or semiconductor has the order of 10 atoms. In a metal, every atom donates at least one free electron for conduction, thus 1 cm of metal contains on the order of 10 free electrons, whereas a 1 cm sample of pure germanium at 20   °C contains about 4.2 × 10 atoms, but only 2.5 × 10 free electrons and 2.5 × 10 holes. The addition of 0.001% of arsenic (an impurity) donates an extra 10 free electrons in

9612-494: The reaction of gallium metal with chlorine gas. Unlike the trifluoride, gallium(III) chloride exists as dimeric molecules, Ga 2 Cl 6 , with a melting point of 78 °C. Equivalent compounds are formed with bromine and iodine, Ga 2 Br 6 and Ga 2 I 6 . Like the other group 13 trihalides, gallium(III) halides are Lewis acids , reacting as halide acceptors with alkali metal halides to form salts containing GaX 4 anions, where X

9720-473: The reaction of gallium with hydrogen sulfide ( H 2 S ) at 950 °C. Alternatively, Ga(OH) 3 can be used at 747 °C: Reacting a mixture of alkali metal carbonates and Ga 2 O 3 with H 2 S leads to the formation of thiogallates containing the [Ga 2 S 4 ] anion. Strong acids decompose these salts, releasing H 2 S in the process. The mercury salt, HgGa 2 S 4 , can be used as

9828-547: The real properties of gallium, such as its density , melting point , oxide character, and bonding in chloride. Mendeleev further predicted that eka-aluminium would be discovered by means of the spectroscope , and that metallic eka-aluminium would dissolve slowly in both acids and alkalis and would not react with air. He also predicted that M 2 O 3 would dissolve in acids to give MX 3 salts, that eka- aluminium salts would form basic salts, that eka-aluminium sulfate should form alums , and that anhydrous MCl 3 should have

9936-629: The resistance of specimens of silver sulfide decreases when they are heated. This is contrary to the behavior of metallic substances such as copper. In 1839, Alexandre Edmond Becquerel reported observation of a voltage between a solid and a liquid electrolyte, when struck by light, the photovoltaic effect . In 1873, Willoughby Smith observed that selenium resistors exhibit decreasing resistance when light falls on them. In 1874, Karl Ferdinand Braun observed conduction and rectification in metallic sulfides , although this effect had been discovered earlier by Peter Munck af Rosenschöld ( sv ) writing for

10044-729: The same structure as ZnS , and have important semiconducting properties. GaP, GaAs, and GaSb can be synthesized by the direct reaction of gallium with elemental phosphorus, arsenic, or antimony. They exhibit higher electrical conductivity than GaN. GaP can also be synthesized by reacting Ga 2 O with phosphorus at low temperatures. Gallium forms ternary nitrides ; for example: Similar compounds with phosphorus and arsenic are possible: Li 3 GaP 2 and Li 3 GaAs 2 . These compounds are easily hydrolyzed by dilute acids and water. Gallium(III) oxide reacts with fluorinating agents such as HF or F 2 to form gallium(III) fluoride , GaF 3 . It

10152-534: The same volume and the electrical conductivity is increased by a factor of 10,000. The materials chosen as suitable dopants depend on the atomic properties of both the dopant and the material to be doped. In general, dopants that produce the desired controlled changes are classified as either electron acceptors or donors . Semiconductors doped with donor impurities are called n-type , while those doped with acceptor impurities are known as p-type . The n and p type designations indicate which charge carrier acts as

10260-472: The same way as the electron. Combined with the negative effective mass of the electrons at the top of the valence band, we arrive at a picture of a positively charged particle that responds to electric and magnetic fields just as a normal positively charged particle would do in a vacuum, again with some positive effective mass. This particle is called a hole, and the collection of holes in the valence band can again be understood in simple classical terms (as with

10368-591: The scale at which the materials are used. A high degree of crystalline perfection is also required, since faults in the crystal structure (such as dislocations , twins , and stacking faults ) interfere with the semiconducting properties of the material. Crystalline faults are a major cause of defective semiconductor devices. The larger the crystal, the more difficult it is to achieve the necessary perfection. Current mass production processes use crystal ingots between 100 and 300 mm (3.9 and 11.8 in) in diameter, grown as cylinders and sliced into wafers . There

10476-425: The semiconductor body by contact with gaseous compounds of the desired element, or ion implantation can be used to accurately position the doped regions. Some materials, when rapidly cooled to a glassy amorphous state, have semiconducting properties. These include B, Si , Ge, Se, and Te, and there are multiple theories to explain them. The history of the understanding of semiconductors begins with experiments on

10584-458: The silicon. After the process is completed and the silicon has reached room temperature, the doping process is done and the semiconducting wafer is almost prepared. Semiconductors are defined by their unique electric conductive behavior, somewhere between that of a conductor and an insulator. The differences between these materials can be understood in terms of the quantum states for electrons, each of which may contain zero or one electron (by

10692-481: The simple crystal structures . The stable phase under normal conditions is orthorhombic with 8 atoms in the conventional unit cell . Within a unit cell, each atom has only one nearest neighbor (at a distance of 244  pm ). The remaining six unit cell neighbors are spaced 27, 30 and 39 pm farther away, and they are grouped in pairs with the same distance. Many stable and metastable phases are found as function of temperature and pressure. The bonding between

10800-445: The so-called " metalloid staircase " on the periodic table . After silicon, gallium arsenide is the second-most common semiconductor and is used in laser diodes , solar cells , microwave-frequency integrated circuits , and others. Silicon is a critical element for fabricating most electronic circuits . Semiconductor devices can display a range of different useful properties, such as passing current more easily in one direction than

10908-427: The system and create electrons and holes. The processes that create or annihilate electrons and holes are called generation and recombination, respectively. In certain semiconductors, excited electrons can relax by emitting light instead of producing heat. Controlling the semiconductor composition and electrical current allows for the manipulation of the emitted light's properties. These semiconductors are used in

11016-407: The term Halbleiter (a semiconductor in modern meaning) in his Ph.D. thesis in 1910. Felix Bloch published a theory of the movement of electrons through atomic lattices in 1928. In 1930, B. Gudden  [ de ] stated that conductivity in semiconductors was due to minor concentrations of impurities. By 1931, the band theory of conduction had been established by Alan Herries Wilson and

11124-416: The two nearest neighbors is covalent ; hence Ga 2 dimers are seen as the fundamental building blocks of the crystal. This explains the low melting point relative to the neighbor elements, aluminium and indium. This structure is strikingly similar to that of iodine and may form because of interactions between the single 4p electrons of gallium atoms, further away from the nucleus than the 4s electrons and

11232-406: The use of semiconductors, with the most important aspect being the integrated circuit (IC), which are found in desktops , laptops , scanners, cell-phones , and other electronic devices. Semiconductors for ICs are mass-produced. To create an ideal semiconducting material, chemical purity is paramount. Any small imperfection can have a drastic effect on how the semiconducting material behaves due to

11340-498: The useful electronic behavior. Using a hot-point probe , one can determine quickly whether a semiconductor sample is p- or n-type. A few of the properties of semiconductor materials were observed throughout the mid-19th and first decades of the 20th century. The first practical application of semiconductors in electronics was the 1904 development of the cat's-whisker detector , a primitive semiconductor diode used in early radio receivers. Developments in quantum physics led in turn to

11448-597: The very stable GaCl 2 contains both gallium(I) and gallium(III) and can be formulated as Ga Ga Cl 4 ; in contrast, the monochloride is unstable above 0 °C, disproportionating into elemental gallium and gallium(III) chloride. Compounds containing Ga–Ga bonds are true gallium(II) compounds, such as GaS (which can be formulated as Ga 2 (S ) 2 ) and the dioxan complex Ga 2 Cl 4 (C 4 H 8 O 2 ) 2 . Strong acids dissolve gallium, forming gallium(III) salts such as Ga(NO 3 ) 3 (gallium nitrate). Aqueous solutions of gallium(III) salts contain

11556-467: The years preceding World War II, infrared detection and communications devices prompted research into lead-sulfide and lead-selenide materials. These devices were used for detecting ships and aircraft, for infrared rangefinders, and for voice communication systems. The point-contact crystal detector became vital for microwave radio systems since available vacuum tube devices could not serve as detectors above about 4000 MHz; advanced radar systems relied on

11664-637: Was sometimes poor. This was later explained by John Bardeen as due to the extreme "structure sensitive" behavior of semiconductors, whose properties change dramatically based on tiny amounts of impurities. Commercially pure materials of the 1920s containing varying proportions of trace contaminants produced differing experimental results. This spurred the development of improved material refining techniques, culminating in modern semiconductor refineries producing materials with parts-per-trillion purity. Devices using semiconductors were at first constructed based on empirical knowledge before semiconductor theory provided

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