Metalorganic vapour phase epitaxy (MOVPE) is a chemical vapour deposition method of
epitaxial growthEpitaxy refers to the method of depositing a monocrystalline film on a monocrystalline substrate. The deposited film is denoted as epitaxial film or epitaxial layer. The term epitaxy comes from the Greek roots epi, meaning "above", and taxis, meaning "in ordered manner". It can be translated "to...
of materials, especially
compound semiconductorA compound semiconductor is a semiconductor compound composed of elements from two or more different groups of the periodic table . For groups 13-15 ,...
s from the surface reaction of
organic compoundAn organic compound is any member of a large class of chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of compounds such as carbonates, simple oxides of carbon and cyanides, as well as the allotropes of carbon, are considered inorganic...
s or
metalorganicsMetalorganic compounds are a class of chemical compounds that contain metals and organic ligands. Metalorganic compounds are used extensively in materials science in applications such as metalorganic vapour phase epitaxy or sol-gel processing using alkoxides...
and metal hydrides containing the required
chemical elementA chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. The term is also used to refer to a pure chemical substance composed of atoms with the same number of protons.Common examples of elements...
s. For example, indium phosphide could be grown in a reactor on a substrate by introducing
TrimethylindiumTrimethylindium , In3, is the preferred metalorganic source of Indium for metalorganic vapour phase epitaxy of indium-containing compound semiconductors, such as InP, InAs, InN, InSb, GaInAs, InGaN, AlGaInP, AlInP, AlInGaNP etc. TMI is a white, crystalline and sublimable solid, with...
((CH
3)
3In) and
phosphinePhosphine is the common name for phosphorus trihydride , also known by the IUPAC name phosphane and, occasionally, phosphamine. It is a colorless, flammable gas with a boiling point of −88 °C at standard pressure...
(PH
3). Alternative names for this process include
organometallic vapour phase epitaxy (
OMVPE),
metalorganic chemical vapour deposition (
MOCVD) and
organometallic chemical vapour deposition (
OMCVD).
Metalorganic vapour phase epitaxy (MOVPE) is a chemical vapour deposition method of
epitaxial growthEpitaxy refers to the method of depositing a monocrystalline film on a monocrystalline substrate. The deposited film is denoted as epitaxial film or epitaxial layer. The term epitaxy comes from the Greek roots epi, meaning "above", and taxis, meaning "in ordered manner". It can be translated "to...
of materials, especially
compound semiconductorA compound semiconductor is a semiconductor compound composed of elements from two or more different groups of the periodic table . For groups 13-15 ,...
s from the surface reaction of
organic compoundAn organic compound is any member of a large class of chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of compounds such as carbonates, simple oxides of carbon and cyanides, as well as the allotropes of carbon, are considered inorganic...
s or
metalorganicsMetalorganic compounds are a class of chemical compounds that contain metals and organic ligands. Metalorganic compounds are used extensively in materials science in applications such as metalorganic vapour phase epitaxy or sol-gel processing using alkoxides...
and metal hydrides containing the required
chemical elementA chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. The term is also used to refer to a pure chemical substance composed of atoms with the same number of protons.Common examples of elements...
s. For example, indium phosphide could be grown in a reactor on a substrate by introducing
TrimethylindiumTrimethylindium , In3, is the preferred metalorganic source of Indium for metalorganic vapour phase epitaxy of indium-containing compound semiconductors, such as InP, InAs, InN, InSb, GaInAs, InGaN, AlGaInP, AlInP, AlInGaNP etc. TMI is a white, crystalline and sublimable solid, with...
((CH
3)
3In) and
phosphinePhosphine is the common name for phosphorus trihydride , also known by the IUPAC name phosphane and, occasionally, phosphamine. It is a colorless, flammable gas with a boiling point of −88 °C at standard pressure...
(PH
3). Alternative names for this process include
organometallic vapour phase epitaxy (
OMVPE),
metalorganic chemical vapour deposition (
MOCVD) and
organometallic chemical vapour deposition (
OMCVD). Formation of the epitaxial layer occurs by final pyrolisis of the constituent chemicals at the substrate surface. In contrast to
molecular beam epitaxyMolecular beam epitaxy , is one of several methods of depositing single crystals. It was invented in the late 1960s at Bell Telephone Laboratories by J. R. Arthur and Alfred Y. Cho.-Method:...
(MBE) the growth of crystals is by chemical reaction and not physical deposition. This takes place not in a
vacuumIn everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty," but in reality, no volume of space can ever be perfectly empty...
, but from the
gasThis page is about the physical properties of gas as a state of matter. For the uses of gases, and other meanings, see Gas .A gas is one of four states of matter. Near absolute zero, a substance exists as a solid...
phase at moderate
pressurePressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
s (2 to 100 k
PaThe pascal is the SI derived unit of pressure, stress, Young's modulus and tensile strength. It is a measure of force per unit area, defined as one newton per square metre...
). As such this technique is preferred for the formation of devices incorporating thermodynamically metastable alloys. It has become the dominant process for the manufacture of laser diodes, solar cells, and
LEDsLEDS can be initials for:* Law Enforcement Data System* Link Eleven Display System* Low Energy Dislocation Structure* Land Electronic Defence System * LEDs * Life-Events and Difficulties Schedule...
.
Reactor components
- A reactor is a chamber made of a material that does not react with the chemicals being used. It must also withstand high temperatures. This chamber is composed by reactor walls, liner, a susceptor
A susceptor is a material used for its ability to absorb electromagnetic energy and convert it to heat . This energy is typically radiofrequency or microwave radiation used in industrial heating processes, and also occasionally in microwave cooking...
, gas injection units, and temperature control units. Usually, the reactor walls are made from stainless steel or quartz. To prevent over heating, cooling water must be flowing through the channels within the reactor walls. Special glassIn general Glass refers to a solid, brittle, transparent material, commonly used for windows, bottles, or eyewear. Examples of glassy materials include, but are not limited to, soda-lime glass, borosilicate glass, acrylic glass, sugar glass, Muscovy-glass, or aluminium oxynitride. The term glass...
es, such as quartz or ceramic, are often used as the liner in the reactor chamber between the reactor wall and the susceptor. A substrate sits on a susceptor which is at a controlled temperature. The susceptor is made from a material resistant to the metalorganic compounds used; graphiteThe mineral graphite is one of the allotropes of carbon. It was named by Abraham Gottlob Werner in 1789 from the Greek γραφειν : "to draw/write", for its use in pencils, where it is commonly called lead, as distinguished from the actual metallic element lead...
is sometimes used. For growing nitrides and related materials, a special coating on the graphite susceptor is necessary to prevent corrosion by ammonia (NH3) gas.
- Gas inlet and switching system. Gas is introduced via devices known as 'bubblers'. In a bubbler a carrier gas (usually nitrogen
Nitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere.Many industrially important...
or hydrogenHydrogen is the chemical element with atomic number 1. It is represented by the symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly flammable diatomic gas with the molecular formula H
2...
) is bubbled through the metalorganic liquidLiquid is one of the principal states of matter. A liquid is a fluid that has the particles loose and can freely form a distinct surface at the boundaries of its bulk material. The surface is a free surface where the liquid is not constrained by a container....
, which picks up some metalorganic vapour and transports it to the reactor. The amount of metalorganic vapour transported depends on the rate of carrier gas flow and the bubbler temperatureIn physics, temperature is a physical property of a system that underlies the common notions of hot and cold; something that feels hotter generally has the higher temperature. Temperature is one of the principal parameters of thermodynamics...
. Allowance must be made for saturated vapours.
- Pressure maintenance system
- Gas Exhaust and cleaning System. Toxic waste products must be converted to liquid or solid wastes for recycling (preferably) or disposal. Ideally processes will be designed to minimize the production of waste products.
Organometallic precursors
- Aluminium
Aluminium or aluminum is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13. It is not soluble in water under normal circumstances....
- Trimethylaluminium
Trimethylaluminium is the chemical compound with the formula Al26, abbreviated as Al2Me6, 2 or the abbreviation TMA...
(TMA or TMAl), Liquid
- Triethylaluminium
Triethylaluminium or TEA is a volatile organometallic compound which is used in various chemical processing and as an ignitor for jet and rocket engines. It is a colorless liquid with melting point -50 °C, boiling point 128-130 °C at 50 mm Hg, flash point at -18 °C, and a characteristic smell...
(TEA or TEAl), Liquid
- Gallium
Gallium is a chemical element that has the symbol Ga and atomic number 31. Elemental gallium does not occur in nature, but as the Ga salt, in trace amounts in bauxite and zinc ores. A soft silvery metallic poor metal, elemental gallium is a brittle solid at low temperatures. As it liquefies...
- Trimethylgallium
Trimethylgallium, Ga
3, often abbreviated to TMG, is the preferred metalorganic source of gallium for metalorganic vapour phase epitaxy of gallium-containing compound semiconductors, such as GaAs, GaN, GaP, GaSb, InGaAs, InGaN, AlGaInP, InGaP and AlInGaNP.TMG is a clear, colorless,...
(TMG or TMGa), Liquid
- Triethylgallium (TEG or TEGa), Liquid
- Indium
Indium is a chemical element with chemical symbol In and atomic number 49. This rare, soft, malleable and easily fusible post-transition metal is chemically similar to aluminium or gallium but more closely resembles zinc .Indium's current primary application is to form transparent electrodes from...
- Trimethylindium
Trimethylindium , In3, is the preferred metalorganic source of Indium for metalorganic vapour phase epitaxy of indium-containing compound semiconductors, such as InP, InAs, InN, InSb, GaInAs, InGaN, AlGaInP, AlInP, AlInGaNP etc. TMI is a white, crystalline and sublimable solid, with...
(TMI or TMIn), Solid
- Triethylindium (TEI or TEIn), Liquid
- Di-isopropylmethylindium (DIPMeIn), Liquid
- Ethyldimethylindium (EDMIn), Liquid
- Germanium
Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon. Germanium has five naturally occurring isotopes ranging in atomic mass number from 70 to 76...
- Isobutylgermane
Isobutylgermane, , 2CHCH2GeH3, is a germanium-containing liquid MOVPE precursor - a novel alternative to the toxic germane gas...
(IBGe), Liquid
- Dimethylamino germanium trichloride (DiMAGeC), Liquid
- Tetramethylgermane (TMGe), Liquid
- Tetraethylgermane (TEGe), Liquid
- Nitrogen
Nitrogen is a chemical element that has the symbol N and atomic number 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78% by volume of Earth's atmosphere.Many industrially important...
- Phenyl hydrazine, Liquid
- Dimethylhydrazine (DMHy), Liquid
- Tertiarybutylamine (TBAm), Liquid
- Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula NH
3. It is normally encountered as a gas with a characteristic pungent odor. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to foodstuffs and fertilizers...
NH3, Gas
- Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus is commonly found in inorganic phosphate rocks. Elemental phosphorus exists in two major forms - white phosphorus and red phosphorus...
- Phosphine
Phosphine is the common name for phosphorus trihydride , also known by the IUPAC name phosphane and, occasionally, phosphamine. It is a colorless, flammable gas with a boiling point of −88 °C at standard pressure...
PH3, Gas
- Tertiarybutyl phosphine (TBP), Liquid
- Bisphosphinoethane (BPE), Liquid
- Arsenic
Arsenic is the chemical element that has the symbol As, atomic number 33 and atomic mass 74.92. Arsenic was first documented by Albertus Magnus in 1250. Arsenic is a notoriously poisonous metalloid with many allotropic forms, including a yellow and several black and grey forms...
- Arsine
Arsine is the chemical compound with the formula AsH3. This flammable, pyrophoric, and highly toxic gas is one of the simplest compounds of arsenic...
AsH3, Gas
- Tertiarybutyl arsine (TBAs), Liquid
- Monoethyl arsine (MEAs), Liquid
- Trimethyl arsine (TMAs), Liquid
- Antimony
Antimony is a chemical element with the symbol Sb and atomic number 51. A metalloid, antimony has four allotropic forms. The stable form of antimony is a blue-white metalloid. Yellow and black antimony are unstable non-metals...
- Trimethyl antimony (TMSb), Liquid
- Triethyl antimony (TESb), Liquid
- Tri-isopropyl antimony (TIPSb), Liquid
- Stibine
Stibine is the chemical compound with the formula SbH3. This colourless gas is the principal covalent hydride of antimony and a heavy analogue of ammonia. The molecule is pyramidal with H–Sb–H angles of 91.7° and Sb–H distances of 1.707 Å...
SbH3, Gas
- Cadmium
Cadmium is a chemical element with the symbol Cd and atomic number 48. The soft, bluish-white transition metal is chemically similar to the two other metals in group 12, zinc and mercury. Similar to zinc it prefers oxidation state +2 in most of its compounds and similar to mercury it shows a low...
- Dimethyl cadmium (DMCd), Liquid
- Diethyl cadmium (DECd), Liquid
- Methyl Allyl Cadmium (MACd), Liquid
- Tellurium
Tellurium is a chemical element that has the symbol Te and atomic number 52. A brittle silver-white metalloid which looks similar to tin, tellurium is chemically related to selenium and sulfur. Tellurium is primarily used in alloys and as a semiconductor.-Characteristics:Tellurium is extremely...
- Selenium
Selenium is a chemical element with the atomic number 34, represented by the chemical symbol Se, an atomic mass of 78.96. It is a nonmetal, chemically related to sulfur and tellurium, and rarely occurs in its elemental state in nature....
- Dimethyl selenide (DMSe), Liquid
- Diethyl selenide (DESe), Liquid
- Di-isopropyl selenide (DIPSe), Liquid
- Zinc
Zinc , also known as spelter, is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
- Dimethylzinc
Zinc methyl is a colorless mobile liquid Zn2, formed by the action of methyl iodide on a zinc at elevated temperature or on zinc sodium alloy....
(DMZ), Liquid
- Diethylzinc
Diethylzinc 2Zn, or DEZ, is an organozinc compound composed of zinc bonded to two ethyl groups. This colourless liquid is an important reagent in organic chemistry and available commercially as solutions of hexanes, heptane, or toluene.-Synthesis:Edward Frankland first reported the...
(DEZ), Liquid
III-V semiconductors
- AlGaAs
Aluminium gallium arsenide is a semiconductor material with very nearly the same lattice constant as GaAs, but a larger bandgap. The x in the formula above is a number between 0 and 1 - this indicates an arbitrary alloy between GaAs and AlAs.The bandgap varies between 1.42 eV and 2.16 eV...
- AlGaInP
- AlGaN
Aluminium gallium nitride is a semiconductor material. It is an alloy of aluminium nitride and gallium nitride.AlGaN is used to manufacture light-emitting diodes operating in blue to ultraviolet region, where wavelengths down to 250 nm were achieved. It is also used in blue semiconductor lasers...
- AlGaP
- GaAsP
Gallium arsenide phosphide is a semiconductor material, an alloy of gallium arsenide and gallium phosphide.Gallium arsenide phosphide is used for manufacturing red, orange and yellow light-emitting diodes. It is often grown on gallium phosphide substrate to form a GaP/GaAsP heterostructure...
- GaAs
- GaN
- GaP
- InAlAs
- InAlP
- InSb
- InGaN
Indium gallium nitride is a semiconductor material made of a mix of gallium nitride and indium nitride . It is a ternary group III/group V direct bandgap semiconductor. Its band gap can be tuned by varying the amount of indium in the alloy...
- GaInAlAs
- GaInAlN
- GaInAsN
- GaInAsP
- GaInAs
- GaInP
- InN
- InP
II-VI semiconductors
- Zinc selenide
Zinc selenide , is a light yellow binary solid compound. It is an intrinsic semiconductor with a band gap of about 2.82 eV at 25 °C. ZnSe rarely occurs in nature. It is found in the mineral stilleite named after Hans Stille.-Applications:...
(ZnSe)
- HgCdTe
- ZnO
- Zinc sulfide
Zinc sulfide is a chemical compound with the formula ZnS. Zinc sulfide is a white- to yellow-colored powder or crystal. It is typically encountered in the more stable cubic form, known also as zinc blende or sphalerite. The hexagonal form is also known both as a synthetic material and as the...
(ZnS)
Environment, Health and Safety
As MOVPE has become well-established production technology, there are equally growing concerns associated with its bearing on personnel and community safety, environmental impact and maximum quantities of hazardous materials (such as gases and metalorganics) permissible in the device fabrication operations. The safety as well as responsible environmental care have become major factors of paramount importance in the MOVPE-based crystal growth of compound semiconductors.
Further reading
1. Gerald B. Stringfellow (1999).
Organometallic Vapor-Phase Epitaxy: Theory and Practice (2nd ed.). Academic Press (ISBN 0-12-673842-4).
2. Manijeh Razeghi (1995).
The MOCVD Challenge: Volumes 1 and 2. Institute of Physics Publishing (ISBN 0-7503-0309-3).