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Gallium arsenide
IUPAC name Gallium arsenide
Identifiers
CAS number [1303-00-0]
SMILES Ga#As
Properties
Molecular formula GaAs
Molar mass 144. IUPAC Nomenclature is a system of naming Chemical compounds and of describing the science of Chemistry in general CAS registry numbers are unique numerical identifiers for Chemical compounds Polymers biological sequences mixtures and Alloys They are also referred to A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes Molar mass, symbol M, is the Mass of one mole of a substance ( Chemical element or Chemical compound) 645 g/mol
Appearance Gray cubic crystals
Melting point

1238°C (1511 K)
Boiling point

°C (? K)
Solubility in water < 0. The melting point of a solid is the temperature range at which it changes state from solid to Liquid. The boiling point of a liquid is the temperature at which the Vapor pressure of the liquid equals the environmental pressure surrounding the liquid Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. Water is a common Chemical substance that is essential for the survival of all known forms of Life. 1 g/100 ml (20°C)
Structure
Crystal structure Zinc Blende
Molecular shape Linear
Hazards
MSDS External MSDS
Main hazards Carcinogenic
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references

Gallium arsenide (GaAs) is a compound of two elements, gallium and arsenic. In Mineralogy and Crystallography, a crystal structure is a unique arrangement of Atoms in a Crystal. The cubic crystal system (or isometric) is a Crystal system where the Unit cell is in the shape of a Cube. Molecular geometry or molecular structure is the three- Dimensional arrangement of the Atoms that constitute a Molecule. A material safety data sheet ( MSDS) is a form containing data regarding the properties of a particular substance Occupational safety and health is a cross-disciplinary area concerned with protecting the Safety, Health and welfare of people engaged in In Chemistry, the standard state of a material is its state at 1 bar (100 Kilopascals exactly A chemical compound is a substance consisting of two or more different elements chemically bonded together in a fixed proportion by Mass. Gallium (ˈgæliəm is a Chemical element that has the symbol Ga and Atomic number 31 Arsenic (ˈɑrsənɪk is a Chemical element that has the symbol As and Atomic number of 33 It is an important semiconductor and is used to make devices such as microwave frequency integrated circuits (ie, MMICs), infrared light-emitting diodes, laser diodes and solar cells. A semiconductor' is a Solid material that has Electrical conductivity in between a conductor and an insulator; it can vary over that Microwaves are electromagnetic waves with Wavelengths ranging from 1 mm to 1 m or frequencies between 0 Microchipsjpg|right|thumb|200px|Microchips ( EPROM memory with a transparent window showing the integrated circuit inside MMIC s or Monolithic Microwave Integrated Circuit s are a type of Integrated circuit (IC devices that operate at Microwave frequencies (300 Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of A laser diode is a Laser where the active medium is a Semiconductor similar to that found in a Light-emitting diode. A solar cell or photovoltaic cell is a device that converts Solar energy into Electricity by the photovoltaic effect.

Contents

Preparation and chemistry

Gallium arsenide can be prepared from the elements and a number of industrial processes use this, for example[1]:

Alternative methods for producing films of GaAs include[2][1] :

2Ga + 2AsCl3 → 2GaAs + 3Cl2
Ga(CH3)3 + AsH3 → GaAs + CH4

Wet etching of GaAs industrially uses an oxidising agent e. The Czochralski process is a method of Crystal growth used to obtain Single crystals of Semiconductors (e Chemical vapor deposition (CVD is a Chemical process used to produce high-purity high-performance solid materials Arsenic trichloride is the Chemical compound with the formula As[[Chlorine Cl3]] Metalorganic vapour phase epitaxy (MOVPE is a Chemical vapour deposition method of epitaxial growth of materials especially Compound semiconductors from Trimethylgallium, Ga(CH33 often abbreviated to TMG, is the preferred Metalorganic source of Gallium for Metalorganic Arsine is the chemical compound with the formula As[[hydrogen H]]3 g. hydrogen peroxide or bromine water[3], and the same strategy has been described in a patent relating to processing scrap components containing GaAs where the Ga3+ is complexed with a hydroxamic acid, "HA"[4]e. Hydrogen peroxide (H2O2 is a very pale blue liquid which appears colorless in a dilute solution slightly more Viscous than water A hydroxamic acid is a class of Chemical compounds sharing the same Functional group in which an Amine is inserted into an Carboxylic acid. g. :

GaAs + H2O2 + "HA" → "GaA" complex + H3AsO4 + 4H2O

Oxidation of GaAs occurs in air and degrades 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 (tBuGaS)7[5]

Applications

GaAs advantages

GaAs has some electronic properties which are superior to those of silicon. Arsenic acid is the Chemical compound with the formula H3AsO4 Gallium(II sulfide, GaS is a Chemical compound of Gallium and Sulfur. Silicon (ˈsɪlɪkən or /ˈsɪlɪkɒn/ silicium is the Chemical element that has the symbol Si and Atomic number 14 It has a higher saturated electron velocity and higher electron mobility, allowing transistors made from it to function at frequencies in excess of 250 GHz. In Physics, electron mobility (or simply mobility) is a quantity relating the Drift velocity of Electrons to the applied Electric field Also, GaAs devices generate less noise than silicon devices when operated at high frequencies. In Science, and especially in Physics and Telecommunication, noise is fluctuations in and the addition of external factors to the stream of target They can also be operated at higher power levels than the equivalent silicon device because they have higher breakdown voltages. Breakdown Voltage of an Insulator is the minimum voltage that causes a portion of an insulator to become electrically conductive. These properties recommend GaAs circuitry in mobile phones, satellite communications, microwave point-to-point links, and some radar systems. A communications satellite (sometimes abbreviated to comsat) is an artificial Satellite stationed in space for the purposes of Telecommunications. Radar is a system that uses electromagnetic waves to identify the range altitude direction or speed of both moving and fixed objects such as Aircraft, ships It is used in the manufacture of Gunn diodes for generation of microwaves. A Gunn diode, also known as a transferred electron device ( TED) is a form of Diode used in high-frequency Electronics.

Another advantage of GaAs is that it has a direct band gap, which means that it can be used to emit light efficiently. In Semiconductor Physics, a direct Bandgap means that the minimum energy of the Conduction band lies directly above the maximum energy of the Silicon has an indirect bandgap and so is very poor at emitting light. In Semiconductor Physics, an indirect bandgap is a Bandgap in which the minimum energy in the Conduction band is shifted by a (Nonetheless, recent advances may make silicon LEDs and lasers possible). A laser is a device that emits Light ( Electromagnetic radiation) through a process called Stimulated emission.

Due to its high switching speed, GaAs would seem to be ideal for computer applications, and for some time in the 1980s many thought that the microelectronics market would switch from silicon to GaAs. The first attempted changes were implemented by the supercomputer vendors Cray Computer Corporation, Convex, and Alliant in an attempt to stay ahead of the ever-improving CMOS microprocessor. A supercomputer is a Computer that is at the frontline of processing capacity particularly speed of calculation (at the time of its introduction Cray Inc ( is a Supercomputer manufacturer based in Seattle Washington. Convex Computer was a company that produced a number of vector Minisupercomputers Supercomputers for small-to-medium-sized businesses Alliant Computer Systems was a computer company that designed and manufactured Parallel computing systems Complementary metal–oxide–semiconductor ( CMOS) (pronounced "see-moss" siːmɔːs ˈsiːmɒs is a major class of Integrated circuits CMOS technology 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. The Cray-3 was a Supercomputer intended to be Cray Research 's successor to the Cray-2.

Silicon's advantages

Silicon has three major advantages over GaAs for integrated circuit manufacture. First, silicon is abundant and cheap to process. Si is highly abundant in the Earth's crust, in the form of silicate minerals. For the Artificial intelligence Androids of the 1990s Science fiction series Space Above and Beyond, see Silicate (AI The economy of scale available to the silicon industry has also reduced the adoption of GaAs.

The second major advantage of Si is the existence of silicon dioxide—one of the best insulators. The Chemical compound silicon dioxide, also known as silica or silox (from the Latin " Silex " is an Oxide An insulator, also called a Dielectric, is a material that resists the flow of Electric current. Silicon dioxide can easily be incorporated onto silicon circuits, and such layers are adherent to the underlying Si. GaAs does not form a stable adherent insulating layer.

The third, and perhaps most important, advantage of silicon is that it possesses a much higher hole mobility. An electron hole is the conceptual and mathematical Opposite of an Electron, useful in the study of Physics and Chemistry. This high mobility allows the fabrication of higher-speed P-channel field effect transistors, which are required for CMOS logic. The field-effect transistor (FET is a type of Transistor that relies on an Electric field to control the shape and hence the conductivity of a 'channel' Complementary metal–oxide–semiconductor ( CMOS) (pronounced "see-moss" siːmɔːs ˈsiːmɒs is a major class of Integrated circuits CMOS technology Because they lack a fast CMOS structure, GaAs logic circuits have much higher power consumption, which has made them unable to compete with silicon logic circuits.

Complex layered structures of gallium arsenide in combination with aluminium arsenide (AlAs) or the alloy AlxGa1-xAs can be grown using molecular beam epitaxy (MBE) or using metalorganic vapour phase epitaxy (MOVPE). Aluminium arsenide (also aluminum arsenide) AlAs, is a Semiconductor material with almost the same Lattice constant as GaAs and Aluminium gallium arsenide (also aluminum gallium arsenide) ( Al x Ga 1-x As) is a Semiconductor material with very Molecular beam Epitaxy (MBE, is one of several methods of depositing Single crystals It was invented in the late 1960s at Bell Telephone Laboratories Metalorganic vapour phase epitaxy (MOVPE is a Chemical vapour deposition method of epitaxial growth of materials especially Compound semiconductors from Because GaAs and AlAs have almost the same lattice constant, the layers have very little induced strain, which allows them to be grown almost arbitrarily thick. The Lattice Constant refers to the constant distance between Unit cells in a Crystal lattice. In Chemistry a Molecule experiences strain when in a Chemical conformation there exist unfavorable bond angles or bond distances By adding several percent manganese to GaAs, GaMnAs can be grown, which is an important magnetic semiconductor. Gallium manganese arsenide (abbreviated GaMnAs, or (GaMnAs, or Ga1-xMnxAs) is a dilute III-V Magnetic semiconductor based Magnetic semiconductors are materials that exhibit both Ferromagnetism (or a similar response and useful Semiconductor properties

Solar cells and detectors

Another important application of GaAs is for high efficiency solar cells. A solar cell or photovoltaic cell is a device that converts Solar energy into Electricity by the photovoltaic effect. In 1970, the first GaAs heterostructure solar cells were created by Zhores Alferov and his team in the USSR. Year 1970 ( MCMLXX) was a Common year starting on Thursday (link shows full calendar of the Gregorian calendar. Zhores Ivanovich Alferov (Жоре́с Ива́нович Алфёров ʐɐˈrʲɛs ɪˈvanəvʲɪtɕ ɐlˈfʲorəf (born March 15 1930) is a Russian The Union of Soviet Socialist Republics (USSR was a constitutionally Socialist state that existed in Eurasia from 1922 to 1991 [6][7][8] In the early 1980s, the efficiency of the best GaAs solar cells surpassed that of silicon solar cells, and in the 1990s GaAs solar cells took over from silicon as the cell type most commonly used for Photovoltaic arrays for satellite applications. A photovoltaic array is a linked collection of Photovoltaic modules which are in turn made of multiple interconnected Solar cells The cells convert 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. Germanium (dʒɚˈmeɪniəm is a Chemical element with the symbol Ge and Atomic number 32 Indium gallium phosphide ( InGaP) is a Semiconductor composed of Indium, Gallium and Phosphorus. This kind of solar cell powers the rovers Spirit and Opportunity, which are exploring Mars' surface. A rover is a Space exploration vehicle designed to move across the surface of a Planet or other Astronomical body. MER-A ( Mars Exploration Rover - A) known as Spirit, is the first of the two rovers of NASA 's Mars Exploration Rover MER-B ( Mars Exploration Rover - B) known as Opportunity, is the second of the two rovers of NASA 's Mars Exploration Also many solar cars utilize GaAs in solar arrays. Notable distance races The two most notable solar car distance (overland races are the World Solar Challenge and the North American Solar Challenge.

Complex designs of AlxGa1-xAs-GaAs devices can be sensitive to infrared radiation (QWIP). A quantum well infrared photodetector ( QWIP) is an Infrared Photodetector made from Semiconductor materials which contain one or more Quantum

GaAs diodes can be used for the detection of x-rays. [9]

Light emission devices

GaAs has been used to produce (near-infrared) laser diodes since the early 1960s. [10]

Single crystals of gallium arsenide can be manufactured by the Bridgeman technique, as the Czochralski process is difficult for this material due to its mechanical properties. A single crystal, also called monocrystal, is a Crystalline Solid in which the Crystal lattice of the entire sample is continuous and unbroken The Bridgman-Stockbarger technique is a method of growing Single crystal Ingots or boules. The Czochralski process is a method of Crystal growth used to obtain Single crystals of Semiconductors (e However, an encapsulated Czochralski method is used to produce ultra-high purity GaAs for semi-insulators.

GaAs is often used a substrate material for the epitaxial growth of other III-V semiconductors including: InGaAs and GaInNAs.

Safety

The toxicological properties of gallium arsenide have not been thoroughly investigated. On one hand, due to its arsenic content, it is considered highly toxic and carcinogenic. Toxicity is the degree to which a substance is able to damage an exposed organism The term carcinogen refers to any substance Radionuclide or radiation that is an agent directly involved in the promotion of Cancer or in the fatation of its propagation On the other hand, the crystal is stable enough that ingested pieces may be passed with negligible absorption by the body. When ground into very fine particles, such as in wafer-polishing processes, the high surface area enables more reaction with water releasing some arsine and/or dissolved arsenic. 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 recently in a review. Trimethylgallium, Ga(CH33 often abbreviated to TMG, is the preferred Metalorganic source of Gallium for Metalorganic Arsine is the chemical compound with the formula As[[hydrogen H]]3 Organometallic chemistry is the study of Chemical compounds containing bonds between Carbon and a Metal. [11]

See also

Related materials

References

  1. ^ a b S. Electronics refers to the flow of charge (moving Electrons through Nonmetal conductors (mainly Semiconductors, whereas electrical The field-effect transistor (FET is a type of Transistor that relies on an Electric field to control the shape and hence the conductivity of a 'channel' The Heterojunction-emitter Bipolar transistor (HEBT is a somewhat unique arrangement with respect to emitter blocking of minority carriers Microchipsjpg|right|thumb|200px|Microchips ( EPROM memory with a transparent window showing the integrated circuit inside A semiconductor' is a Solid material that has Electrical conductivity in between a conductor and an insulator; it can vary over that Semiconductor devices are Electronic components that exploit the electronic properties of Semiconductor materials principally Silicon, Germanium A solar cell or photovoltaic cell is a device that converts Solar energy into Electricity by the photovoltaic effect. Magnetic semiconductors are materials that exhibit both Ferromagnetism (or a similar response and useful Semiconductor properties Photomixing is a technique that uses two lasers to generate Terahertz radiation. Aluminium arsenide (also aluminum arsenide) AlAs, is a Semiconductor material with almost the same Lattice constant as GaAs and Indium arsenide, InAs, or indium monoarsenide, is a Semiconductor material, a Semiconductor composed of Indium and Arsenic Gallium antimonide (GaSb is a semiconducting compound of Gallium and Antimony of the III-V family Gallium phosphide () a Phosphide of Gallium, is a compound Semiconductor material with an indirect Band gap Aluminium gallium arsenide (also aluminum gallium arsenide) ( Al x Ga 1-x As) is a Semiconductor material with very Indium gallium arsenide ( InGaAs) is a Semiconductor composed of Indium, Gallium and Arsenic. Gallium arsenide phosphide () is a Semiconductor material, an alloy of Gallium arsenide and Gallium phosphide. Gallium nitride ( is a very hard material commonly used in bright LEDs since the 1990s Metalorganic vapour phase epitaxy (MOVPE is a Chemical vapour deposition method of epitaxial growth of materials especially Compound semiconductors from Trimethylgallium, Ga(CH33 often abbreviated to TMG, is the preferred Metalorganic source of Gallium for Metalorganic Arsine is the chemical compound with the formula As[[hydrogen H]]3 J. Moss, A. Ledwith (1987) The Chemistry of the Semiconductor Industry, Springer, ISBN 0216920051
  2. ^ Lesley Smart, Elaine A. Moore, (2005), Solid State Chemistry: An Introduction ,CRC, ISBN 0748775161
  3. ^ M. R. Brozel, G. E. Stillman (1996)Properties of Gallium Arsenide, IEE Inspec, ISBN 085296885X
  4. ^ Oxidative dissolution of gallium arsenide and separation of gallium from arsenic, United States Patent 4759917, Coleman, J. P. ,Monzyk, B. F (1988)
  5. ^ 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)
  6. ^ Alferov, Zh. I. , V. M. Andreev, M. B. Kagan, I. I. Protasov, and V. G. Trofim, 1970, ‘‘Solar-energy converters based on p-n AlxGa1-xAs-GaAs heterojunctions,’’ Fiz. Tekh. Poluprovodn. 4, 2378 (Sov. Phys. Semicond. 4, 2047 (1971))]
  7. ^ Nanotechnology in energy applications, pdf, p. 24
  8. ^ Nobel Lecture by Zhores Alferov, pdf, p. Zhores Ivanovich Alferov (Жоре́с Ива́нович Алфёров ʐɐˈrʲɛs ɪˈvanəvʲɪtɕ ɐlˈfʲorəf (born March 15 1930) is a Russian 6
  9. ^ Glasgow University report on CERN detector
  10. ^ R. C. Miller, F. M. Ryan and P. R. Emtage, “Uniaxial Strain Effects in Gallium Arsenide Laser Diodes,” 7th Intl. Conf. Phys. Semicond. , Academic Press, Paris, 1964.
  11. ^ Environment, health and safety issues for sources used in MOVPE growth of compound semiconductors; D V Shenai-Khatkhate, R Goyette, R L DiCarlo and G Dripps, Journal of Crystal Growth, vol. 1-4, pp. 816-821 (2004); doi:10.1016/j.jcrysgro.2004.09.007

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