Indium phosphide (InP) is a binary
semiconductor
A semiconductor is a material which has an electrical resistivity and conductivity, electrical conductivity value falling between that of a electrical conductor, conductor, such as copper, and an insulator (electricity), insulator, such as glas ...
composed of
indium
Indium is a chemical element with the symbol In and atomic number 49. Indium is the softest metal that is not an alkali metal. It is a silvery-white metal that resembles tin in appearance. It is a post-transition metal that makes up 0.21 parts p ...
and
phosphorus
Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...
. It has a face-centered cubic ("
zincblende
Sphalerite (sometimes spelled sphaelerite) is a sulfide mineral with the chemical formula . It is the most important ore of zinc. Sphalerite is found in a variety of deposit types, but it is primarily in sedimentary exhalative, Mississippi-Va ...
")
crystal structure
In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystal, crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric pat ...
, identical to that of
GaAs
Gallium arsenide (GaAs) is a III-V direct band gap semiconductor with a zinc blende crystal structure.
Gallium arsenide is used in the manufacture of devices such as microwave frequency integrated circuits, monolithic microwave integrated circui ...
and most of the
III-V semiconductors
Semiconductor materials are nominally small band gap insulators. The defining property of a semiconductor material is that it can be compromised by doping it with impurities that alter its electronic properties in a controllable way.
Because of t ...
.
Manufacturing
Indium phosphide can be prepared from the reaction of
white phosphorus
Elemental phosphorus can exist in several allotropes, the most common of which are white and red solids. Solid violet and black allotropes are also known. Gaseous phosphorus exists as diphosphorus and atomic phosphorus.
White phosphorus
White ...
and
indium iodide There are three sets of Indium halides, the trihalides, the monohalides, and several intermediate halides. In the monohalides the oxidation state of indium is +1 and their proper names are indium(I) fluoride, indium(I) chloride, indium(I) bromide a ...
at 400 °C., also by direct combination of the purified elements at high temperature and pressure, or by thermal decomposition of a mixture of a trialkyl indium compound and
phosphine
Phosphine (IUPAC name: phosphane) is a colorless, flammable, highly toxic compound with the chemical formula , classed as a pnictogen hydride. Pure phosphine is odorless, but technical grade samples have a highly unpleasant odor like rotting ...
.
Uses
InP is used in high-power and high-frequency electronics because of its superior
electron velocity
In physics, a drift velocity is the average velocity attained by charged particles, such as electrons, in a material due to an electric field. In general, an electron in a conductor will propagate randomly at the Fermi velocity, resulting in an a ...
with respect to the more common semiconductors
silicon
Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic tab ...
and
gallium arsenide
Gallium arsenide (GaAs) is a III-V direct band gap semiconductor with a Zincblende (crystal structure), zinc blende crystal structure.
Gallium arsenide is used in the manufacture of devices such as microwave frequency integrated circuits, monoli ...
.
It was used with
indium gallium arsenide
Indium gallium arsenide (InGaAs) (alternatively gallium indium arsenide, GaInAs) is a ternary alloy (chemical compound) of indium arsenide (InAs) and gallium arsenide (GaAs). Indium and gallium are ( group III) elements of the periodic table whil ...
to make a record breaking
pseudomorphic heterojunction bipolar transistor The heterojunction bipolar transistor (HBT) is a type of bipolar junction transistor (BJT) which uses differing semiconductor materials for the emitter and base regions, creating a heterojunction. The HBT improves on the BJT in that it can handle ...
that could operate at 604 GHz.
It also has a
direct bandgap
In semiconductor physics, the band gap of a semiconductor can be of two basic types, a direct band gap or an indirect band gap. The minimal-energy state in the conduction band and the maximal-energy state in the valence band are each characteriz ...
, making it useful for
optoelectronics
Optoelectronics (or optronics) is the study and application of electronic devices and systems that find, detect and control light, usually considered a sub-field of photonics. In this context, ''light'' often includes invisible forms of radiatio ...
devices like
laser diode
file:Laser diode chip.jpg, The laser diode chip removed and placed on the eye of a needle for scale
A laser diode (LD, also injection laser diode or ILD, or diode laser) is a semiconductor device similar to a light-emitting diode in which a di ...
s. The company
Infinera
Infinera Corporation is a San Jose, California-based vertically integrated manufacturer of Wavelength division multiplexing (WDM)-based packet optical transmission equipment and IP transport technologies for the telecommunications service provide ...
uses indium phosphide as its major technological material for manufacturing
photonic integrated circuit
A photonic integrated circuit (PIC) or integrated optical circuit is a microchip containing two or more photonic components which form a functioning circuit. This technology detects, generates, transports, and processes light. Photonic integrated c ...
s for the
optical telecommunications industry, to enable
wavelength-division multiplexing
In fiber-optic communications, wavelength-division multiplexing (WDM) is a technology which multiplexes a number of optical carrier signals onto a single optical fiber by using different wavelengths (i.e., colors) of laser light. This techniq ...
[The Light Brigade](_blank)
appeared in ''Red Herring'' in 2002. applications.
InP is also used as a substrate for
epitaxial
Epitaxy refers to a type of crystal growth or material deposition in which new crystalline layers are formed with one or more well-defined orientations with respect to the crystalline seed layer. The deposited crystalline film is called an epit ...
indium gallium arsenide
Indium gallium arsenide (InGaAs) (alternatively gallium indium arsenide, GaInAs) is a ternary alloy (chemical compound) of indium arsenide (InAs) and gallium arsenide (GaAs). Indium and gallium are ( group III) elements of the periodic table whil ...
based opto-electronic devices.
Another use of Indium Phosphide (InP) is in photonic integrated circuits (PICs). InP photonic integrated circuits have active laser generation, amplification, control, and detection. This makes them an ideal component for communication and sensing applications.
Applications
The application fields of InP splits up into three main areas. It is used as the basis for optoelectronic components, high-speed electronics, and photovoltaics
There is still a vastly under-utilized, yet technically exciting zone in the
electromagnetic spectrum
The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies.
The electromagnetic spectrum covers electromagnetic waves with frequencies ranging from ...
between
microwaves
Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency rang ...
and
infrared
Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...
, often referred to as
terahertz.
Electromagnetic waves
In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visible) lig ...
in this range possess hybrid properties they show high-frequency- and optical characteristics simultaneously. InP based components unlock this spectral range for important new applications.
Optoelectronic applications
InP based lasers and LEDs can emit light in the very broad range of 1200 nm up to 12 µm. This light is used for fibre based Telecom and Datacom applications in all areas of the digitalised world. Light is also used for sensing applications. On one hand there are spectroscopic applications, where a certain wavelength is needed to interact with matter to detect highly diluted gases for example. Optoelectronic terahertz is used in ultra-sensitive spectroscopic analysers, thickness measurements of polymers and for the detection of multilayer coatings in the automotive industry. On the other hand there is a huge benefit of specific InP lasers because they are eye safe. The radiation is absorbed in the vitreous body of the human eye and cannot harm the retina.
Telecommunications/Data communications
Indium Phosphide (InP) is used to produce efficient lasers, sensitive photodetectors and modulators in the wavelength window typically used for telecommunications, i.e., 1550 nm wavelengths, as it is a direct bandgap III-V compound semiconductor material. The wavelength between about 1510 nm and 1600 nm has the lowest attenuation available on optical fibre (about 0.2 dB/km). InP is a commonly used material for the generation of laser signals and the detection and conversion of those signals back to electronic form. Wafer diameters range from 2-4 inches.
Applications are:
• Long-haul optical fibre connections over great distance up to 5000 km typically >10 Tbit/s
• Metro ring access networks
• Company networks and data center
• Fibre to the home
• Connections to wireless 3G, LTE and 5G base stations
• Free space satellite communication
Optical sensing
Spectroscopic Sensing aiming environmental protection and identification of dangerous substances
• A growing field is sensing based on the wavelength regime of InP. One example for Gas Spectroscopy is drive test equipment with real-time measurement of (CO, CO
2, NO
X 2">r NO + NO2.
• Another example is FT-IR-Spectrometer VERTEX with a terahertz source. The terahertz radiation is generated from the beating signal of 2 InP lasers and an InP antenna that transforms the optical signal to the terahertz regime.
• Stand-Off detection of traces of explosive substances on surfaces, e.g. for safety applications on airports or crime scene investigation after assassination attempts.
• Quick verification of traces of toxic substances in gases and liquids (including tap water) or surface contaminations down to the ppb level.
• Spectroscopy for non-destructive product control of e.g. food (early detection of spoiled foodstuff). Researchers of
Eindhoven University of Technology
The Eindhoven University of Technology ( nl, Technische Universiteit Eindhoven), abbr. TU/e, is a public technical university in the Netherlands, located in the city of Eindhoven. In 2020–21, around 14,000 students were enrolled in its BSc a ...
and MantiSpectra have already demonstrated the application of an integrated near-infrared spectral sensor for milk. In addition, it has been proven that this technology can also be applied to plastics and illicit drugs.
• Spectroscopy for many novel applications, especially in air pollution control are being discussed today and implementations are on the way.
LiDAR systems for the automotive sector and industry 4.0
Widely discussed in the LiDAR arena is the wavelength of the signal. While some players have opted for 830-to-940-nm wavelengths to take advantage of available optical components, companies (including Blackmore,
Neptec, Aeye, and
Luminar) are increasingly turning to longer wavelengths in the also-well-served 1550-nm wavelength band, as those wavelengths allow laser powers roughly 100 times higher to be employed without compromising public safety. Lasers with emission wavelengths longer than ≈ 1.4 μm are often called “eye-safe” because light in that wavelength range is strongly absorbed in the eye's cornea, lens and vitreous body and therefore cannot damage the sensitive retina).
• LiDAR-based sensor technology can provide a high level of object identification and classification with three-dimensional (3D) imaging techniques.
• The automotive industry will adopt a chip-based, low cost solid state LiDAR sensor technology instead of large, expensive, mechanical LiDAR systems in the future.
• For the most advanced chip-based LiDAR systems, InP will play an important role and will enable autonomous driving. (Report: Blistering Growth for Automotive Lidar, Stewart Wills). The longer eye safe wavelength is also more appropriate dealing with real world conditions like dust, fog and rain.
High-speed electronics
Today's semiconductor technology allows the creation and detection of very high frequencies of 100 GHz and higher. Such components find their applications in wireless high-speed data communication (directional radio), radars (compact, energy-efficient and highly resolving), and radiometric sensing e. g. for weather- or atmospheric observations.
InP is also used to realize high-speed microelectronics and such semiconductor devices are the fastest devices available today. Typically, microelectronics on InP is based on
High-electron-mobility transistors (HEMT) or on
Heterojunction bipolar transistors (HBT). The sizes and volumes of both transistors based on InP material is very small: 0.1 µm x 10 µm x 1 µm. Typical substrate thicknesses are < 100 µm. These transistors are assembled into circuits and modules for the following applications:
• Security scanning systems: Imaging systems for airport security imaging and scanners for civil security applications
• Wireless communications: High-speed 5G wireless communications will explore InP technology due to its superior performance. Such systems operate at frequencies beyond 100 GHz in order to support high data rates
• Biomedical applications: Millimeter-wave and THz spectrometers are employed for non-invasive diagnostics in medical applications from cancer tissue identification, diabetes detection, to medical diagnostics using human exhaled air.
• Non-destructive testing: Industrial applications employ scanning systems for quality control in e.g. automotive paint thickness applications and defects in composite materials in aerospace
• Robotics: Robotic vision is essentially based on high resolution imaging radar systems at millimetre-waves
• Radiometric sensing: Almost all components and pollutions in the atmosphere show characteristic absorptions/emissions (fingerprints) in the microwave range. InP allows to fabricate small, lightweight and mobile systems to identify such substances.
Photovoltaic applications
Photovoltaic cells with highest efficiencies of up to 46% (Press Release, Fraunhofer ISE, 1. December 2014) implement InP substrates to achieve an optimal bandgap combination to efficiently convert solar radiation into electrical energy. Today, only InP substrates achieve the lattice constant to grow the required low bandgap materials with high crystalline quality. Research groups all over the world are looking for replacements due to the high costs of these materials. However, up to now all other options yield lower material qualities and hence lower conversion efficiencies. Further research focusses on the re-use of the InP substrate as template for the production of further solar cells.
Also today’s state-of-the-art high-efficiency solar cells for concentrator photovoltaics (CPV) and for space applications use (Ga)InP and other III-V compounds to achieve the required bandgap combinations. Other technologies, such as Si solar cells, provide only half the power than III-V cells and furthermore show much stronger degradation in the harsh space environment. Finally, Si-based solar cells are also much heavier than III-V solar cells and yield to a higher amount of space debris. One way to significantly increase conversion efficiency also in terrestrial PV systems is the use of similar III-V solar cells in CPV systems where only about one-tenth of a percent of the area is covered by high-efficiency III-V solar cells.
Chemistry
Indium phosphide also has one of the longest-lived
optical phonon
In physics, a phonon is a collective excitation in a periodic, elastic arrangement of atoms or molecules in condensed matter, specifically in solids and some liquids. A type of quasiparticle, a phonon is an excited state in the quantum mechani ...
s of any compound with the
zincblende crystal structure
Sphalerite (sometimes spelled sphaelerite) is a sulfide mineral with the chemical formula . It is the most important ore of zinc. Sphalerite is found in a variety of deposit types, but it is primarily in sedimentary exhalative, Mississippi-Va ...
.
Quaternary compounds
Indium phosphide is sometimes alloyed with indium antimonide and Indium arsenide to create a quaternary alloy with a range of band gaps that depend on the different concentration ratios of its components (InP, InAs and InSb), such quaternary alloys was under extensive theoretical studies to study the effect of pressure and temperature
on its properties.
References
External links
Extensive site on the physical properties of indium phosphide(Ioffe institute)
Band structure and carrier concentration of InP.InP conference seriesat IEEE
Indium Phosphide: Transcending frequency and integration limits. Semiconductor TODAY Compounds&AdvancedSilicon • Vol. 1 • Issue 3 • September 2006
{{Phosphides
Phosphides
Indium compounds
Inorganic phosphorus compounds
Optoelectronics
III-V semiconductors
III-V compounds
IARC Group 2A carcinogens
Zincblende crystal structure