Photodetectors called photosensors, are sensors of light or other electromagnetic radiation. A photo detector has a p -- n junction; the absorbed photons make electron–hole pairs in the depletion region. Photodiodes and photo transistors are a few examples of photo detectors. Solar cells convert some of the light energy absorbed into electrical energy. Photodetectors may be classified by their mechanism for detection: Photoemission or photoelectric effect: Photons cause electrons to transition from the conduction band of a material to free electrons in a vacuum or gas. Thermal: Photons cause electrons to transition to mid-gap states decay back to lower bands, inducing phonon generation and thus heat. Polarization: Photons induce changes in polarization states of suitable materials, which may lead to change in index of refraction or other polarization effects. Photochemical: Photons induce a chemical change in a material. Weak interaction effects: photons induce secondary effects such as in photon drag detectors or gas pressure changes in Golay cells.
Photodetectors may be used in different configurations. Single sensors may detect overall light levels. A 1-D array of photodetectors, as in a spectrophotometer or a Line scanner, may be used to measure the distribution of light along a line. A 2-D array of photodetectors may be used as an image sensor to form images from the pattern of light before it. A photodetector or array is covered by an illumination window, sometimes having an anti-reflective coating. There are a number of performance metrics called figures of merit, by which photodetectors are characterized and compared Spectral response: The response of a photodetector as a function of photon frequency. Quantum efficiency: The number of carriers generated per photon. Responsivity: The output current divided by total light power falling upon the photodetector. Noise-equivalent power: The amount of light power needed to generate a signal comparable in size to the noise of the device. Detectivity: The square root of the detector area divided by the noise equivalent power.
Gain: The output current of a photodetector divided by the current directly produced by the photons incident on the detectors, i.e. the built-in current gain. Dark current: The current flowing through a photodetector in the absence of light. Response time: The time needed for a photodetector to go from 10% to 90% of final output. Noise spectrum: The intrinsic noise voltage or current as a function of frequency; this can be represented in the form of a noise spectral density. Nonlinearity: The RF-output is limited by the nonlinearity of the photodetector Grouped by mechanism, photodetectors include the following devices: Gaseous ionization detectors are used in experimental particle physics to detect photons and particles with sufficient energy to ionize gas atoms or molecules. Electrons and ions generated by ionization cause a current flow. Photomultiplier tubes containing a photocathode which emits electrons when illuminated, the electrons are amplified by a chain of dynodes. Phototubes containing a photocathode which emits electrons when illuminated, such that the tube conducts a current proportional to the light intensity.
Microchannel plate detectors are silicon-based photomultipliers. Active-pixel sensors are image sensors. Made in a complementary metal-oxide-semiconductor process, known as CMOS image sensors, APSs are used in cell phone cameras, web cameras, some DSLRs. Cadmium zinc telluride radiation detectors can operate in direct-conversion mode at room temperature, unlike some other materials which require liquid nitrogen cooling, their relative advantages include high sensitivity for x-rays and gamma-rays, due to the high atomic numbers of Cd and Te, better energy resolution than scintillator detectors. Charge-coupled devices, which are used to record images in astronomy, digital photography, digital cinematography. Before the 1990s, photographic plates were most common in astronomy; the next generation of astronomical instruments, such as the Astro-E2, include cryogenic detectors. HgCdTe infrared detectors. Detection occurs when an infrared photon of sufficient energy kicks an electron from the valence band to the conduction band.
Such an electron is collected by a suitable external readout integrated circuits and transformed into an electric signal. LEDs which are reverse-biased to act as photodiodes. See LEDs as Photodiode Light Sensors. Photoresistors or Light Dependent Resistors; the resistance of LDRs decreases with increasing intensity of light falling on it. Photodiodes which can operate in photovoltaic mode or photoconductive mode. Photodiodes are combined with low-noise analog electronics to convert the photocurrent into a voltage that can be digitized. Phototransistors, which act like amplifying photodiodes. Quantum dot photoconductors or photodiodes, which can handle wavelengths in the visible and infrared spectral regions. Semiconductor detectors are employed as particle detectors. Silicon drift detectors are X-ray radiation detectors used in x-ray spectrometry and electron microscopy. Photovoltaic cells or solar cells which produce a voltage and supply an electric current when illuminated. Bolometers measure the power of incident electromagnetic radiation via the heating of a material with a temperature-dependent electrical resistance.
A microbolometer is a specific type of bolometer used as a detector in a thermal camera. Cryogenic detectors are sufficiently sensitive to measure the energy of single x-ray and infrared photons
In the broadest definition, a sensor is a device, module, or subsystem whose purpose is to detect events or changes in its environment and send the information to other electronics a computer processor. A sensor is always used with other electronics. Sensors are used in everyday objects such as touch-sensitive elevator buttons and lamps which dim or brighten by touching the base, besides innumerable applications of which most people are never aware. With advances in micromachinery and easy-to-use microcontroller platforms, the uses of sensors have expanded beyond the traditional fields of temperature, pressure or flow measurement, for example into MARG sensors. Moreover, analog sensors such as potentiometers and force-sensing resistors are still used. Applications include manufacturing and machinery and aerospace, medicine and many other aspects of our day-to-day life. A sensor's sensitivity indicates how much the sensor's output changes when the input quantity being measured changes. For instance, if the mercury in a thermometer moves 1 cm when the temperature changes by 1 °C, the sensitivity is 1 cm/°C.
Some sensors can affect what they measure. Sensors are designed to have a small effect on what is measured. Technological progress allows more and more sensors to be manufactured on a microscopic scale as microsensors using MEMS technology. In most cases, a microsensor reaches a higher speed and sensitivity compared with macroscopic approaches. A good sensor obeys the following rules:: it is sensitive to the measured property it is insensitive to any other property to be encountered in its application, it does not influence the measured property. Most sensors have a linear transfer function; the sensitivity is defined as the ratio between the output signal and measured property. For example, if a sensor measures temperature and has a voltage output, the sensitivity is a constant with the units; the sensitivity is the slope of the transfer function. Converting the sensor's electrical output to the measured units requires dividing the electrical output by the slope. In addition, an offset is added or subtracted.
For example, -40 must be added to the output. For an analog sensor signal to be processed, or used in digital equipment, it needs to be converted to a digital signal, using an analog-to-digital converter. Since sensors cannot replicate an ideal transfer function, several types of deviations can occur which limit sensor accuracy: Since the range of the output signal is always limited, the output signal will reach a minimum or maximum when the measured property exceeds the limits; the full scale range defines the minimum values of the measured property. The sensitivity may in practice differ from the value specified; this is called a sensitivity error. This is an error in the slope of a linear transfer function. If the output signal differs from the correct value by a constant, the sensor has an offset error or bias; this is an error in the y-intercept of a linear transfer function. Nonlinearity is deviation of a sensor's transfer function from a straight line transfer function; this is defined by the amount the output differs from ideal behavior over the full range of the sensor noted as a percentage of the full range.
Deviation caused by rapid changes of the measured property over time is a dynamic error. This behavior is described with a bode plot showing sensitivity error and phase shift as a function of the frequency of a periodic input signal. If the output signal changes independent of the measured property, this is defined as drift. Long term drift over months or years is caused by physical changes in the sensor. Noise is a random deviation of the signal. A hysteresis error causes the output value to vary depending on the previous input values. If a sensor's output is different depending on whether a specific input value was reached by increasing vs. decreasing the input the sensor has a hysteresis error. If the sensor has a digital output, the output is an approximation of the measured property; this error is called quantization error. If the signal is monitored digitally, the sampling frequency can cause a dynamic error, or if the input variable or added noise changes periodically at a frequency near a multiple of the sampling rate, aliasing errors may occur.
The sensor may to some extent be sensitive to properties other than the property being measured. For example, most sensors are influenced by the temperature of their environment. A hysteresis error causes the output value to vary depending on the previous input values. If a sensor's output is different depending on whether a specific input value was reached by increasing vs. decreasing the input the sensor has a hysteresis error. All these deviations can be classified as random errors. Systematic errors can sometimes be compensated for by means of some kind of calibration strategy. Noise is a random error that can be reduced by signal processing, such as filtering at the expense of the dynamic behavior of the sensor; the resolution of a sensor is the smallest change it can detect in the quantity that it is measuring. The resolution of a sensor with a digital output is the resolution of the digital output; the resolution is related to the precision with which the mea
Mercury cadmium telluride
HgCdTe or mercury cadmium telluride is an alloy of cadmium telluride and mercury telluride with a tunable bandgap spanning the shortwave infrared to the long wave infrared regions. The amount of cadmium in the alloy 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 1.5 electronvolts at room temperature. HgTe is a semimetal. Mixing these two substances allows one to obtain any bandgap between 0 and 1.5 eV. HgCdTe has a zincblende structure with two interpenetrating face-centered cubic lattices offset by ao in the primitive cell; the cations form the yellow sublattice while the Te anions form the grey sublattice per the adjacent diagram. The electron mobility of HgCdTe with a large Hg content is high. Among common semiconductors used for infrared detection, only InSb and InAs surpass electron mobility of HgCdTe at room temperature. At 80 K, the electron mobility of Hg0.8Cd0.2Te can be several hundred thousand cm2/.
Electrons have a long ballistic length at this temperature. The intrinsic carrier concentration is given by n i = ⋅ 10 14 ⋅ E g 0.75 ⋅ T 1.5 ⋅ e − E g ⋅ q 2 ⋅ k ⋅ t where k is Boltzmann's constant, q is the elementary electric charge, t is the material temperature, x is the percentage of cadmium concentration, Eg is the bandgap given by E g = − 0.302 + 1.93 ⋅ x + ⋅ t ⋅ − 0.81 ⋅ x 2 + 0.832 ⋅ x 3 Using the relationship λ p = 1.24 E g, where λ is in µm and Eg. is in electron volts, one can obtain the cutoff wavelength as a function of x and t: λ p = − 1 Two types of Auger recombination affect HgCdTe: Auger 1 and Auger 7 recombination. Auger 1 recombination involves two electrons and one hole, where an electron and a hole combine and the remaining electron receives energy equal to or greater than the band gap. Auger 7 recombination involves one electron and two holes; the Auger 1 minority carrier lifetime for intrinsic HgCdTe is given by τ A u g e r 1 = 2.12 ⋅ 10 − 14 ⋅ E g ⋅ e q ⋅ E g k ⋅ t F F 2 ⋅ 1.5 where FF is the overlap integral.
The Auger 1 minority carrier lifetime for doped HgCdTe is given by τ A u g e r 1 d o p e d ( t
Photovoltaics is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics and electrochemistry. A photovoltaic system employs solar panels, each comprising a number of solar cells, which generate electrical power. PV installations may be ground-mounted, rooftop mounted or wall mounted; the mount may use a solar tracker to follow the sun across the sky. Solar PV has specific advantages as an energy source: once installed, its operation generates no pollution and no greenhouse gas emissions, it shows simple scalability in respect of power needs and silicon has large availability in the Earth’s crust. PV systems have the major disadvantage that the power output works best with direct sunlight, so about 10-25% is lost if a tracking system is not used. Dust and other obstructions in the atmosphere diminish the power output. Another important issue is the concentration of the production in the hours corresponding to main insolation, which do not match the peaks in demand in human activity cycles.
Unless current societal patterns of consumption and electrical networks adjust to this scenario, electricity still needs to be stored for use or made up by other power sources hydrocarbons. Photovoltaic systems have long been used in specialized applications, stand-alone and grid-connected PV systems have been in use since the 1990s, they were first mass-produced in 2000, when German environmentalists and the Eurosolar organization got government funding for a ten thousand roof program. Advances in technology and increased manufacturing scale have in any case reduced the cost, increased the reliability, increased the efficiency of photovoltaic installations. Net metering and financial incentives, such as preferential feed-in tariffs for solar-generated electricity, have supported solar PV installations in many countries. More than 100 countries now use solar PV. After hydro and wind powers, PV is the third renewable energy source in terms of global capacity. At the end of 2016, worldwide installed PV capacity increased to more than 300 gigawatts, covering two percent of global electricity demand.
China, followed by Japan and the United States, is the fastest growing market, while Germany remains the world's largest producer, with solar PV providing seven percent of annual domestic electricity consumption. With current technology, photovoltaics recoups the energy needed to manufacture them in 1.5 years in Southern Europe and 2.5 years in Northern Europe. The term "photovoltaic" comes from the Greek φῶς meaning "light", from "volt", the unit of electro-motive force, the volt, which in turn comes from the last name of the Italian physicist Alessandro Volta, inventor of the battery; the term "photo-voltaic" has been in use in English since 1849. Photovoltaics are best known as a method for generating electric power by using solar cells to convert energy from the sun into a flow of electrons by the photovoltaic effect. Solar cells produce direct current electricity from sunlight which can be used to power equipment or to recharge a battery; the first practical application of photovoltaics was to power orbiting satellites and other spacecraft, but today the majority of photovoltaic modules are used for grid connected power generation.
In this case an inverter is required to convert the DC to AC. There is a smaller market for off-grid power for remote dwellings, recreational vehicles, electric cars, roadside emergency telephones, remote sensing, cathodic protection of pipelines. Photovoltaic power generation employs solar panels composed of a number of solar cells containing a photovoltaic material. Copper solar cables connect modules and sub-fields; because of the growing demand for renewable energy sources, the manufacturing of solar cells and photovoltaic arrays has advanced in recent years. Solar photovoltaic power generation has long been seen as a clean energy technology which draws upon the planet’s most plentiful and distributed renewable energy source – the sun. Cells require protection from the environment and are packaged in solar panels. Photovoltaic power capacity is measured as maximum power output under standardized test conditions in "Wp"; the actual power output at a particular point in time may be less than or greater than this standardized, or "rated", depending on geographical location, time of day, weather conditions, other factors.
Solar photovoltaic array capacity factors are under 25%, lower than many other industrial sources of electricity. For best performance, terrestrial PV systems aim to maximize the time. Solar trackers achieve this by moving PV panels to follow the sun; the increase can be by as much as 50 % in summer. Static mounted. Panels are set to latitude tilt, an angle equal to the latitude, but performance can be improved by adjusting the angle for summer or winter; as with other semiconductor devices, temperatures above room temperature reduce the performance of photovoltaics. A number of solar panels may be mounted vertically above each other in a tower, if the zenith distance of the Sun is greater than zero, the tower can be turned horizontally as a whole and each panels additionally around a horizontal axis. In such a tower the panels can follow the Sun exactly; such a device may be described as a ladder mounted on a turnable disk. Each step of that ladder is the middle axis of a rectangular solar panel.
In case the zenith distance of the Sun reaches zero, the "ladder" may be rotated
Infrared radiation, sometimes called infrared light, is electromagnetic radiation with longer wavelengths than those of visible light, is therefore invisible to the human eye, although IR at wavelengths up to 1050 nanometers s from specially pulsed lasers can be seen by humans under certain conditions. IR wavelengths extend from the nominal red edge of the visible spectrum at 700 nanometers, to 1 millimeter. Most of the thermal radiation emitted by objects near room temperature is infrared; as with all EMR, IR carries radiant energy and behaves both like a wave and like its quantum particle, the photon. Infrared radiation was discovered in 1800 by astronomer Sir William Herschel, who discovered a type of invisible radiation in the spectrum lower in energy than red light, by means of its effect on a thermometer. More than half of the total energy from the Sun was found to arrive on Earth in the form of infrared; the balance between absorbed and emitted infrared radiation has a critical effect on Earth's climate.
Infrared radiation is emitted or absorbed by molecules when they change their rotational-vibrational movements. It excites vibrational modes in a molecule through a change in the dipole moment, making it a useful frequency range for study of these energy states for molecules of the proper symmetry. Infrared spectroscopy examines transmission of photons in the infrared range. Infrared radiation is used in industrial, military, law enforcement, medical applications. Night-vision devices using active near-infrared illumination allow people or animals to be observed without the observer being detected. Infrared astronomy uses sensor-equipped telescopes to penetrate dusty regions of space such as molecular clouds, detect objects such as planets, to view red-shifted objects from the early days of the universe. Infrared thermal-imaging cameras are used to detect heat loss in insulated systems, to observe changing blood flow in the skin, to detect overheating of electrical apparatus. Extensive uses for military and civilian applications include target acquisition, night vision and tracking.
Humans at normal body temperature radiate chiefly at wavelengths around 10 μm. Non-military uses include thermal efficiency analysis, environmental monitoring, industrial facility inspections, detection of grow-ops, remote temperature sensing, short-range wireless communication and weather forecasting. Infrared radiation extends from the nominal red edge of the visible spectrum at 700 nanometers to 1 millimeter; this range of wavelengths corresponds to a frequency range of 430 THz down to 300 GHz. Below infrared is the microwave portion of the electromagnetic spectrum. Sunlight, at an effective temperature of 5,780 kelvins, is composed of near-thermal-spectrum radiation, more than half infrared. At zenith, sunlight provides an irradiance of just over 1 kilowatt per square meter at sea level. Of this energy, 527 watts is infrared radiation, 445 watts is visible light, 32 watts is ultraviolet radiation. Nearly all the infrared radiation in sunlight is shorter than 4 micrometers. On the surface of Earth, at far lower temperatures than the surface of the Sun, some thermal radiation consists of infrared in the mid-infrared region, much longer than in sunlight.
However, black body or thermal radiation is continuous: it gives off radiation at all wavelengths. Of these natural thermal radiation processes, only lightning and natural fires are hot enough to produce much visible energy, fires produce far more infrared than visible-light energy. In general, objects emit infrared radiation across a spectrum of wavelengths, but sometimes only a limited region of the spectrum is of interest because sensors collect radiation only within a specific bandwidth. Thermal infrared radiation has a maximum emission wavelength, inversely proportional to the absolute temperature of object, in accordance with Wien's displacement law. Therefore, the infrared band is subdivided into smaller sections. A used sub-division scheme is: NIR and SWIR is sometimes called "reflected infrared", whereas MWIR and LWIR is sometimes referred to as "thermal infrared". Due to the nature of the blackbody radiation curves, typical "hot" objects, such as exhaust pipes appear brighter in the MW compared to the same object viewed in the LW.
The International Commission on Illumination recommended the division of infrared radiation into the following three bands: ISO 20473 specifies the following scheme: Astronomers divide the infrared spectrum as follows: These divisions are not precise and can vary depending on the publication. The three regions are used for observation of different temperature ranges, hence different environments in space; the most common photometric system used in astronomy allocates capital letters to different spectral regions according to filters used. These letters are understood in reference to atmospheric windows and appear, for instance, in the titles of many papers. A third scheme divides up the band based on the response of various detectors: Near-infrared: from 0.7 to 1.0 µm. Short-wave infrared: 1.0 to 3 µm. InGaAs covers to about 1.8 µm. Mid-wave infrared: 3 to 5 µm (defined by the atmospheric window and covered by indium antimonide and mercury cadmium telluride and by lead
A bolometer is a device for measuring the power of incident electromagnetic radiation via the heating of a material with a temperature-dependent electrical resistance. It was invented in 1878 by the American astronomer Samuel Pierpont Langley. A bolometer is a cake element, such as a thin layer of metal, connected to a thermal reservoir through a thermal link; the result is that any radiation impinging on the absorptive element raises its temperature above that of the reservoir – the greater the absorbed power, the higher the temperature. The intrinsic thermal time constant, which sets the speed of the detector, is equal to the ratio of the heat capacity of the absorptive element to the thermal conductance between the absorptive element and the reservoir; the temperature change can be measured directly with an attached resistive thermometer, or the resistance of the absorptive element itself can be used as a thermometer. Metal bolometers work without cooling, they are produced from thin foils or metal films.
Today, most bolometers use superconductor absorptive elements rather than metals. These devices can be operated at cryogenic temperatures, enabling greater sensitivity. Bolometers are directly sensitive to the energy left inside the absorber. For this reason they can be used not only for ionizing particles and photons, but for non-ionizing particles, any sort of radiation, to search for unknown forms of mass or energy; the most sensitive bolometers are slow to reset. On the other hand, compared to more conventional particle detectors, they are efficient in energy resolution and in sensitivity, they are known as thermal detectors. The first bolometer used by Langley consisted of two platinum strips covered with lampblack. One strip was shielded from one exposed to it; the strips formed two branches of a Wheatstone bridge, fitted with a sensitive galvanometer and connected to a battery. Electromagnetic radiation falling on the exposed strip would change its resistance. By 1880, Langley's bolometer was refined enough to detect thermal radiation from a cow a quarter of a mile away.
This radiant-heat detector is sensitive to differences in temperature of one hundred-thousandth of a degree Celsius. This instrument enabled him to thermally detect across a broad spectrum, noting all the chief Fraunhofer lines, he discovered new atomic and molecular absorption lines in the invisible infrared portion of the electromagnetic spectrum. Nikola Tesla asked Dr. Langley if he could use his bolometer for his power transmission experiments in 1892. Thanks to that first use, he succeeded in making the first demonstration between West Point and his laboratory on Houston Street. While bolometers can be used to measure radiation of any frequency, for most wavelength ranges there are other methods of detection that are more sensitive. For sub-millimeter wavelengths, bolometers are among the most sensitive available detectors, are therefore used for astronomy at these wavelengths. To achieve the best sensitivity, they must be cooled to a fraction of a degree above absolute zero. Notable examples of bolometers employed in submillimeter astronomy include the Herschel Space Observatory, the James Clerk Maxwell Telescope, the Stratospheric Observatory for Infrared Astronomy.
The term bolometer is used in particle physics to designate an unconventional particle detector. They use the same principle described above; the bolometers are sensitive not only to every form of energy. The operating principle is similar to that of a calorimeter in thermodynamics. However, the approximations, ultra low temperature, the different purpose of the device make the operational use rather different. In the jargon of high energy physics, these devices are not called cows since this term is used for a different type of detector, their use as particle detectors was proposed from the beginning of the 20th century, but the first regular, though pioneering, use was only in the 1980s because of the difficulty associated with cooling and operating a system at cryogenic temperature. They can still be considered to be at the developmental stage. A microbolometer is a specific type of bolometer used as a detector in a thermal camera, it is a grid of vanadium oxide or amorphous silicon heat sensors atop a corresponding grid of silicon.
Infrared radiation from a specific range of wavelengths strikes the vanadium oxide or amorphous silicon, changes its electrical resistance. This resistance change is measured and processed into temperatures which can be represented graphically; the microbolometer grid is found in three sizes, a 640×480 array, a 320×240 array or less expensive 160×120 array. Different arrays provide the same resolution with larger array providing a wider field of view. Larger, 1024×768 arrays were announced in 2008; the hot electron bolometer operates at cryogenic temperatures within a few degrees of absolute zero. At these low temperatures, the electron system in a metal is weakly coupled to the phonon system. Power coupled to the electron system drives it out of thermal equilibrium with the phonon system, creating hot electrons. Phonons in the metal are well-coupled to substrate phonons and act as a thermal reservoir. In describing the performance of the HEB, the relevant heat capacity is the electronic heat capacity and the relevant thermal conductance is the electron
Indium antimonide is a crystalline compound made from the elements indium and antimony. It is a narrow-gap semiconductor material from the III-V group used in infrared detectors, including thermal imaging cameras, FLIR systems, infrared homing missile guidance systems, in infrared astronomy; the indium antimonide detectors are sensitive between 1–5 µm wavelengths. Indium antimonide was a common detector in the old, single-detector mechanically-scanned thermal imaging systems. Another application is as a terahertz radiation source; the intermetallic compound was first reported by Liu and Peretti in 1951, who gave its homogeneity range, structure type, lattice constant. Polycrystalline ingots of InSb were prepared by Heinrich Welker in 1952, although they were not pure by today's semiconductor standards. Welker was interested in systematically studying the semiconducting properties of the III-V compounds, he noted how InSb appeared to have a small direct band gap and a high electron mobility. InSb crystals have been grown by slow cooling from liquid melt at least since 1954.
InSb has powder with vitreous lustre. When subjected to temperatures over 500 °C, it melts and decomposes, liberating antimony and antimony oxide vapors; the crystal structure is zincblende with a 0.648 nm lattice constant. InSb is a narrow-gap semiconductor with an energy band gap of 0.17 eV at 300 K and 0.23 eV at 80 K. Undoped InSb possesses the largest ambient-temperature electron mobility, electron drift velocity, ballistic length of any known semiconductor, except for carbon nanotubes. Indium antimonide photodiode detectors are photovoltaic, generating electric current when subjected to infrared radiation. InSb's internal quantum efficiency is 100% but is a function of the thickness for near bandedge photons. Like all narrow bandgap materials InSb detectors require periodic recalibrations, increasing the complexity of the imaging system; this added complexity is worthwhile where extreme sensitivity is required, e.g. in long-range military thermal imaging systems. InSb detectors require cooling, as they have to operate at cryogenic temperatures.
Large arrays are available. HgCdTe and PtSi are materials with similar use. A layer of indium antimonide sandwiched between layers of aluminium indium antimonide can act as a quantum well. In such a heterostructure InSb/AlInSb has been shown to exhibit a robust quantum Hall effect; this approach is studied in order to construct fast transistors. Bipolar transistors operating at frequencies up to 85 GHz were constructed from indium antimonide in the late 1990s; some models suggest. Indium antimonide semiconductor devices are capable of operating with voltages under 0.5 V, reducing their power requirements. InSb can be grown by solidifying a melt from the liquid state, or epitaxially by liquid phase epitaxy, hot wall epitaxy or molecular beam epitaxy, it can be grown from organometallic compounds by MOVPE. Thermal image detectors using photodiodes or photoelectromagnetic detectors Magnetic field sensors using magnetoresistance or the Hall effect Fast transistors; this is due to the high carrier mobility of InSb.
In some of the detectors of the Infrared Array Camera on the Spitzer Space Telescope National Compound Semiconductor Roadmap at the Office of Naval Research Material safety data sheet at University of Texas at Dallas