HgCdTe or Mercury cadmium telluride (also Cadmium Mercury Telluride or CMT) is an alloy of CdTe and HgTe and is sometimes claimed to be the third semiconductor of technological importance after Si and GaAs. The amount of cadmium (Cd) in the alloy (the alloy composition) can be chosen so as to tune the optical absorption of the material to the desired infrared wavelength. CdTe is a semiconductor with a bandgap of approximately 1.5 eV at room temperature. HgTe is a semimetal, hence its bandgap energy is zero. Mixing these two elements allows one to obtain any bandgap between 0 and 1.5 eV. General Name, Symbol, Number mercury, Hg, 80 Chemical series transition metals Group, Period, Block 12, 6, d Appearance silvery white Atomic mass 200. ... General Name, Symbol, Number cadmium, Cd, 48 Chemical series transition metals Group, Period, Block 12, 5, d Appearance silvery gray metallic Atomic mass 112. ... Telluride is either: A compound of a metal with the element Tellurium. ... Alloy is a combination, either in solution or compound, of two or more elements, which has a combination of at least one metal, and where the resultant material has metallic properties. ... Cadmium telluride (CdTe) is a crystalline compound formed from cadmium and tellurium with a zinc blende (cubic) crystal structure (space group F43m). ... Mercury telluride (HgTe) is a binary chemical compound of mercury and tellurium. ... Cover of brochure The International System of Units. ... Gallium arsenide (GaAs) is a chemical compound composed of gallium and arsenic. ... Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of microwave radiation. ... The wavelength is the distance between repeating units of a wave pattern. ... A semiconductor is a material with an electrical conductivity that is intermediate between that of an insulator and a conductor. ... In solid state physics and related applied fields, the band gap is the energy difference between the top of the valence band and the bottom of the conduction band in insulators and semiconductors. ... Together with the metals and nonmetals, the metalloids (in Greek metallon = metal and eidos = sort - also called semimetals) form one of the three categories of chemical elements as classified by ionization and bonding properties. ... An electronvolt (symbol: eV) is the amount of kinetic energy gained by a single unbound electron when it passes through an electrostatic potential difference of one volt, in vacuum. ...

HgCdTe is usually referred to as MerCad Telluride, or simply MerCad in the Infrared sensors community. Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of microwave radiation. ...

Energy gap as a function of cadmium composition.

Image File history File links HgCdTe_Eg_vs_x. ... Image File history File links HgCdTe_Eg_vs_x. ...

Properties

Electronic

The electron mobility of HgCdTe with a large Hg content is very high. At room temperature only InSb and InAs of common semeiconductors used for infrared detection surpass HgCdTe's electron mobility. At 80K the electron mobility of Hg_0.8Cd_0.2Te can be several hundred thousand cm²/V/s. Electrons also have a long ballistic length at this temperature; their mean free path can be several micrometres. In physics, electron mobility (or simply, mobility), is used to describe the relation between drift velocity of electrons or holes in a solid material or electrons/ions in a gas, and an applied electric field. ... Indium antimonide (InSb) is a narrow gap semiconductor material from the group the (III-V group) used in infrared detectors, including thermal imaging cameras, FLIR systems, infrared homing missile guidance systems, and in infrared astronomy. ... Indium arsenide, InAs, or indium monoarsenide, is a semiconductor material, a semiconductor composed of indium and arsenic. ... For sound waves in an enclosure, the mean free path is the average distance the wave travels between reflections off of the enclosures walls. ...

Mechanical

HgCdTe is a soft material due to the weak bonds Hg forms with tellurium. It is a softer material than any common III-V semiconductor. The Mohs hardness of HgTe is 1.9, CdTe is 2.9 and Hg_0.5Cd_0.5Te is 4. The hardness of lead salts is lower still. In materials science, hardness is the characteristic of a solid material expressing its resistance to permanent deformation. ...

Thermal

The thermal conductivity of HgCdTe is low. This means that it is unuitable for high power devices. Although, light emitting diodes and lasers have been made in HgCdTe they must be operated cold to be efficient. Various light-emitting diodes (5 mm reds, 3 mm greens and yellows) A light-emitting diode (LED) is a semiconductor device that emits incoherent monochromatic light when electrically biased in the forward direction. ...

Optical

HgCdTe is transparent in the infrared below the energy gap. The refractive index is high reaching nearly 4 for high Hg content HgCdTe. The refractive index of a material is the factor by which the phase velocity of electromagnetic radiation is slowed relative to vacuum. ...

Infrared detection

HgCdTe is the only common material that can detect infrared radiation in both of the accessible atmospheric windows. These are from 3 to 5 µm (the mid-wave infrared window, abbreviated MWIR) and from 10 to 12 µm (the long-wave window, LWIR). Detection in the MWIR and LWIR windows is obtained using 30% [(Hg_0.7Cd_0.3)Te] and 20% [(Hg_0.8Cd_0.2)Te] cadmium respectively. HgCdTe can also detect in the short wave infrared SWIR atmospheric windows of 2.2 to 2.4 µm and 1.5 to 1.8 µm. An infrared detector is a detector that reacts to infrared (IR) radiation. ... Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of microwave radiation. ... Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of microwave radiation. ... Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of microwave radiation. ...

Owing to its cost, the use of HgCdTe has so far been restricted to the military field and infrared astronomy research. Military technology depends on HgCdTe for night vision. In particular, the US air force makes extensive use of HgCdTe on all aircraft, and to equip airborne smart bombs. A variety of heat-seeking missiles are also equipped with HgCdTe detectors. HgCdTe detector arrays can also be found at most of the worlds major research telescopes including several satellites. Infrared astronomy is the branch of astronomy and astrophysics which deals with objects visible in infrared (IR) radiation. ... Night-vision is seeing in the dark. ... Seal of the Air Force. ... BOLT-117 laser guided bomb Precision-guided munitions (smart munitions or smart bombs) are self-guiding weapons intended to maximize damage to the target while minimizing collateral damage. Because the damage effects of an explosive weapon scale as a power law with distance, quite modest improvements in accuracy (and hence... 50 cm refracting telescope at Nice Observatory. ...

The main limitation of LWIR HgCdTe-based detectors is that they need cooling to temperatures near that of liquid nitrogen (77K), to reduce noise due to thermally excited current carriers (see cooled infrared camera). MWIR HgCdTe cameras can be operated at temperatures accessible to thermoelectric coolers with a small performance penalty. Hence, HgCdTe detectors are heavy and require maintenance. On the other side, HgCdTe enjoys much higher speed of detection and is much more sensitive than some of its cheaper competitors. General Name, Symbol, Number Nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15 (VA), 2 , p Density 1. ... An infrared camera, or a thermographic camera, is a device that forms an image using infrared radiation, similar to a common camera that forms an image using visible light. ... Thermoelectricity is the conversion from heat differentials to electricity or vice versa. ...

HgCdTe is often a material of choice for detectors in Fourier Transform Infrared Spectrometer (FTIR) instruments. This is because of the large spectral range of HgCdTe detectors and also the high quantum efficiency.

HgCdTe can be used as a heterodyne detector, in which the interference between a local source and returned laser light is detected. In this case it can detect sources such as CO₂ lasers. In heterodyne detection mode HgCdTe can be uncooled, although greater sensitivity is achieved by cooling. Photodiodes, photoconductors or photoelectromagnetic (PEM) modes can be used. A bandwidth in excess of 1GHz can be achieved with photodiode detectors. In telecommunications, to heterodyne is to generate new frequencies by mixing two or more signals in a nonlinear device such as a vacuum tube, transistor, or diode mixer. ...

The main competitors of HgCdTe are less sensitive Si-based bolometers (see uncooled infrared camera), InSb, III-V semiconductor superlattices and more sensitive quantum dot, quantum well detectors in materials such as GaAs and photon-counting superconducting tunnel junction (STJ) arrays. A bolometer is a device for measuring incident electromagnetic radiation. ... An infrared camera, or a thermographic camera, is a device that forms an image using infrared radiation, similar to a common camera that forms an image using visible light. ... Indium antimonide (InSb) is a narrow gap semiconductor group the (III-V group) used in infrared detectors, including thermal imaging cameras. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Fluorescence induced by exposure to ultraviolet light in vials containing various sized Cadmium selenide (CdSe) quantum dots. ... A quantum well is a potential well that confines particles in one dimension, forcing them to occupy a planar region. ... Gallium arsenide (GaAs) is a chemical compound composed of gallium and arsenic. ... The effect The Josephson effect is named after British physicist Brian David Josephson who predicted its existence in 1962. ...

In HgCdTe, detection occurs when an infrared photon of sufficient energy kicks an electron from the conduction band to the valence band. Such an electron is collected by a suitable external readout circuit (ROIC) and transformed into an electric signal. In physics, the photon (from Greek φως, phōs, meaning light) is the quantum of the electromagnetic field; for instance, light. ... Properties The electron is a fundamental subatomic particle that carries a negative electric charge. ... In semiconductors and insulators, the conduction band is the range of electron energy, higher than that of the valence band, sufficient to make the electrons free to accelerate under the influence of an applied electric field and thus constitute an electric current. ... In solids, the valence band is the highest range of electron energies where electrons are normally present at zero temperature. ...

In a bolometer, light heats up a tiny piece of material. The temperature change is measured and transformed into an electric signal. A bolometer is a device for measuring incident electromagnetic radiation. ...

Mercury zinc telluride has better chemical, thermal, and mechanical stability characteristics than HgCdTe. It has a steeper change of energy gap with mercury composition than HgCdTe, making compositional control harder. Mercury zinc telluride (HgZnTe, MZT) is a telluride of mercury and zinc, an alloy of mercury telluride and zinc telluride. ...

HgCdTe growth techniques

Bulk crystal growth

The first large scale growth method was bulk recrystallization of a liquid melt. This was the main growth method from the late 1950s to the early 1970s. // Events and No. ... The 1970s decade refers to the years from 1970 to 1979, inclusive. ...

Epitaxial growth

Highly pure and crystalline HgCdTe is fabricated by epitaxy on either CdTe or CdZnTe substrates. CdZnTe is a compound semiconductor, the lattice parameter of which can be exactly matched to that of HgCdTe. This eliminates most defects from the epilayer of HgCdTe. CdTe was developed as an alternative substrate in the '90s. It is not lattice-matched to HgCdTe, but is much cheaper, as it can be grown by epitaxy on silicon (Si) or germanium (Ge) substrates. Epitaxy is the growth of crystals of one material on the crystal face of another (heteroepitaxy) or the same (homoepitaxy) material, such that the two materials have a defined relative structural orientation. ... Cadmium zinc telluride, (CdZnTe) or CZT, is (as the name indicates) a compound of cadmium, zinc and tellurium or more strictly speaking, an alloy of cadmium telluride and zinc telluride. ... General Name, Symbol, Number germanium, Ge, 32 Chemical series metalloids Group, Period, Block 14, 4, p Appearance grayish white Atomic mass 72. ...

Liquid phase epitaxy (LPE), in which a substrate is repeatedly dipped into a liquid melt, gives the best results in terms of crystalline quality, and is still a common technique of choice for industrial production.

In recent years, molecular beam epitaxy (MBE) has become widespread because of its ability to stack up layers of different alloy composition. This allows simultaneous detection at several wavelengths. Furthermore, MBE, and also MOVPE, allow growth on large area substrates such as CdTe on Si or Ge, whereas LPE does not allow such substrates to be used. Molecular beam epitaxy, abbreviated MBE, is the deposition of one or more pure materials onto a single crystal wafer, one layer of atoms at a time, under ultra-high vacuum, forming a perfect crystal. ... Metalorganic vapour phase epitaxy (MOVPE) is a chemical vapour deposition method of epitaxial growth of materials, especially semiconductors from the pyrolysis of organic compounds containing the required chemical elements. ...

Research laboratories working on HgCdTe

US

• The University of Illinois at Chicago
• University of Michigan, Ann Arbor
• US Army Night Vision Laboratory (Virginia)
• US Army Research Laboratory (Maryland)

The University of Illinois at Chicago (UIC) is a public, state-supported research university. ... This article is about the University of Michigan in Ann Arbor. ...

Australia

• Microelectronics Research Group, The University of Western Australia.

Motto: Cygnis Insignis (Distinguished by its swans) Nickname: Wildflower State Other Australian states and territories Capital Perth Government Governor Premier Const. ...

France

• Commissariat à l'Energie Atomique of Grenoble (CEA-LETI-SLIR)
• SOFRADIR Sa

The SLIR (Service Laboratoire Infra Rouge) was founded at the end of the 1970s to coordinate the development of night vision equipment for the French army. ...

Germany

• AIM INFRAROT MODULE GmbH

UK

• QinetiQ Ltd.
• SELEX SAS Ltd.

QinetiQ (LSE: QQ.) (pronounced kĭ-nĕtĭk, as in kinetic energy) is a British defence technology company, created out of the greater part of the government agency DERA when it was split up in June 2001 (with the smaller part forming Dstl). ... SELEX Sensors and Airborne Systems (Selex S&AS) is a major avionics joint venture created by the merger of Finmeccanicas Galileo Avionica and BAE Systems Avionics. ...

Russia

• Institute of Semiconductor Physics, Novosibirsk.

Novosibirsk (Russian Новосиби́рск, pop. ...

Poland

• VIGO System S.A.

New Zealand

• Spitfire Semiconductors Ltd [1]

This list is not exhaustive.

See also

Related materials

• Mercury telluride, Cadmium telluride, Mercury zinc telluride.

Mercury telluride (HgTe) is a binary chemical compound of mercury and tellurium. ... Cadmium telluride (CdTe) is a crystalline compound formed from cadmium and tellurium with a zinc blende (cubic) crystal structure (space group F43m). ... Mercury zinc telluride (HgZnTe, MZT) is a telluride of mercury and zinc, an alloy of mercury telluride and zinc telluride. ...

Other infrared detection materials

• Indium antimonide, Indium arsenide, Lead selenide, QWIP.

Indium antimonide (InSb) is a narrow gap semiconductor material from the group the (III-V group) used in infrared detectors, including thermal imaging cameras, FLIR systems, infrared homing missile guidance systems, and in infrared astronomy. ... Indium arsenide, InAs, or indium monoarsenide, is a semiconductor material, a semiconductor composed of indium and arsenic. ... Lead selenide (PbSe), or lead(II) selenide, a selenide of lead, is a semiconductor material. ...

Other

• Infrared, thermography.

Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of microwave radiation. ... Thermography can refer to a printing process and an imaging process. ...

References

• Preparation and properties of HgTe and mixed crystals of HgTe-CdTe, W. D. Lawson, S. Nielson, E. H. Putley, and A. S. Young, J. Phys. Chem. Solids vol. 9, 325–329 (1959). (Earliest known reference)
• Properties of Narrow-Gap Cadmium-Based Compounds Ed. P. Capper (INSPEC, IEE, London, UK, 1994) ISBN 0852968809
• HgCdTe Infrared Detectors, P. Norton, Opto-Electronics Review vol. 10(3), 159–174 (2002) [2]
• Band structures of HgCdTe and HgZnTe alloys and superlattices, A B Chen, Y M Lai-Hsu, S Krishnamurthy and M A Berding, Semicond. Sci. Technol. vol. 5 pp. S100-S102 (1990) DOI:10.1088/0268-1242/5/3S/021
• E. Finkman and Y. Nemirovsky, J. Appl. Phys. 50, 4356 (1979).
• E. Finkman and S.E. Schacham, J. Appl. Phys. 56, 2896 (1984).
• HOTEYE: a novel thermal camera using higher operating temperature infrared detectors, G. J. Bowen et al., Proceedings of the SPIE, Vol. 5783, pp. 392-400 (2005) DOI:10.1117/12.603305 .

A digital object identifier (or DOI) is a permanent identifier (permalink) given to a World Wide Web file or other Internet document so that if its Internet address changes, users will be redirected to its new address. ... The International Society for Optical Engineering (or SPIE) is an international non-for-profit organization for the promotion of optical engineering. ... A digital object identifier (or DOI) is a permanent identifier (permalink) given to a World Wide Web file or other Internet document so that if its Internet address changes, users will be redirected to its new address. ...

External links

• US National compound Semiconductor Roadmap at the Office of Naval Research.
• National Pollutant Inventory - Mercury and compounds Fact Sheet