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. [1] Because of their application in the computer and photovoltaic industry—in devices such as transistors, lasers, and solar cells—the search for new semiconductor materials and the improvement of existing materials is an important field of study in materials science.
Most commonly used semiconductor materials are crystalline inorganic solids. These materials are classified according to the periodic table groups of their constituent atoms.
Different semiconductor materials differ in their properties. Thus, in comparison with silicon, compound semiconductors have both advantages and disadvantages. For example, gallium arsenide (GaAs) has six times higher electron mobility than silicon, which allows faster operation; wider band gap, which allows operation of power devices at higher temperatures, and gives lower thermal noise to low power devices at room temperature; its direct band gap gives it more favorable optoelectronic properties than the indirect band gap of silicon; it can be alloyed to ternary and quaternary compositions, with adjustable band gap width, allowing light emission at chosen wavelengths, which makes possible matching to the wavelengths most efficiently transmitted through optical fibers. GaAs can be also grown in a semi-insulating form, which is suitable as a lattice-matching insulating substrate for GaAs devices. Conversely, silicon is robust, cheap, and easy to process, whereas GaAs is brittle and expensive, and insulation layers cannot be created by just growing an oxide layer; GaAs is therefore used only where silicon is not sufficient. [2]
By alloying multiple compounds, some semiconductor materials are tunable, e.g., in band gap or lattice constant. The result is ternary, quaternary, or even quinary compositions. Ternary compositions allow adjusting the band gap within the range of the involved binary compounds; however, in case of combination of direct and indirect band gap materials there is a ratio where indirect band gap prevails, limiting the range usable for optoelectronics; e.g. AlGaAs LEDs are limited to 660 nm by this. Lattice constants of the compounds also tend to be different, and the lattice mismatch against the substrate, dependent on the mixing ratio, causes defects in amounts dependent on the mismatch magnitude; this influences the ratio of achievable radiative/nonradiative recombinations and determines the luminous efficiency of the device. Quaternary and higher compositions allow adjusting simultaneously the band gap and the lattice constant, allowing increasing radiant efficiency at wider range of wavelengths; for example AlGaInP is used for LEDs. Materials transparent to the generated wavelength of light are advantageous, as this allows more efficient extraction of photons from the bulk of the material. That is, in such transparent materials, light production is not limited to just the surface. Index of refraction is also composition-dependent and influences the extraction efficiency of photons from the material. [3]
This section needs additional citations for verification .(September 2021) |
A compound semiconductor is a semiconductor compound composed of chemical elements of at least two different species. These semiconductors form for example in periodic table groups 13–15 (old groups III–V), for example of elements from the Boron group (old group III, boron, aluminium, gallium, indium) and from group 15 (old group V, nitrogen, phosphorus, arsenic, antimony, bismuth). The range of possible formulae is quite broad because these elements can form binary (two elements, e.g. gallium(III) arsenide (GaAs)), ternary (three elements, e.g. indium gallium arsenide (InGaAs)) and quaternary alloys (four elements) such as aluminium gallium indium phosphide (AlInGaP)) alloy and Indium arsenide antimonide phosphide (InAsSbP). The properties of III-V compound semiconductors are similar to their group IV counterparts. The higher ionicity in these compounds, and especially in the II-VI compound, tends to increase the fundamental bandgap with respect to the less ionic compounds. [4]
Metalorganic vapor-phase epitaxy (MOVPE) is the most popular deposition technology for the formation of compound semiconducting thin films for devices.[ citation needed ] It uses ultrapure metalorganics and/or hydrides as precursor source materials in an ambient gas such as hydrogen.
Other techniques of choice include:
Group | Elem. | Material | Formula | Band gap (eV) | Gap type | Description |
---|---|---|---|---|---|---|
IV | 1 | Silicon | Si | 1.12 [5] [6] | indirect | Used in conventional crystalline silicon (c-Si) solar cells, and in its amorphous form as amorphous silicon (a-Si) in thin-film solar cells. Most common semiconductor material in photovoltaics; dominates worldwide PV market; easy to fabricate; good electrical and mechanical properties. Forms high quality thermal oxide for insulation purposes. Most common material used in the fabrication of integrated circuits. |
IV | 1 | Germanium | Ge | 0.67 [5] [6] | indirect | Used in early radar detection diodes and first transistors; requires lower purity than silicon. A substrate for high-efficiency multijunction photovoltaic cells. Very similar lattice constant to gallium arsenide. High-purity crystals used for gamma spectroscopy. May grow whiskers, which impair reliability of some devices. |
IV | 1 | Diamond | C | 5.47 [5] [6] | indirect | Excellent thermal conductivity. Superior mechanical and optical properties. High carrier mobilities [7] and high electric breakdown field [8] at room temperature as excellent electronics characteristics. Extremely high nanomechanical resonator quality factor. [9] |
IV | 1 | Gray tin, α-Sn | Sn | 0 [10] [11] | semimetal | Low temperature allotrope (diamond cubic lattice). |
IV | 2 | Silicon carbide, 3C-SiC | SiC | 2.3 [5] | indirect | Used for early yellow LEDs |
IV | 2 | Silicon carbide, 4H-SiC | SiC | 3.3 [5] | indirect | Used for high-voltage and high-temperature applications |
IV | 2 | Silicon carbide, 6H-SiC | SiC | 3.0 [5] | indirect | Used for early blue LEDs |
VI | 1 | Sulfur, α-S | S8 | 2.6 [12] | ||
VI | 1 | Gray (trigonal) selenium | Se | 1.83–2.0 [13] [14] | indirect | Used in selenium rectifiers and solar cells. [15] Band gap depends on fabrication conditions. |
VI | 1 | Red selenium | Se | 2.05 | indirect | [16] |
VI | 1 | Tellurium | Te | 0.33 [17] | ||
III-V | 2 | Boron nitride, cubic | BN | 6.36 [18] | indirect | Potentially useful for ultraviolet LEDs |
III-V | 2 | Boron nitride, hexagonal | BN | 5.96 [18] | quasi-direct | Potentially useful for ultraviolet LEDs |
III-V | 2 | Boron nitride nanotube | BN | 5.5 [19] | ||
III-V | 2 | Boron phosphide | BP | 2.1 [20] | indirect | |
III-V | 2 | Boron arsenide | BAs | 1.82 | direct | Ultrahigh thermal conductivity for thermal management; Resistant to radiation damage, possible applications in betavoltaics. |
III-V | 2 | Boron arsenide | B12As2 | 3.47 | indirect | Resistant to radiation damage, possible applications in betavoltaics. |
III-V | 2 | Aluminium nitride | AlN | 6.28 [5] | direct | Piezoelectric. Not used on its own as a semiconductor; AlN-close GaAlN possibly usable for ultraviolet LEDs. Inefficient emission at 210 nm was achieved on AlN. |
III-V | 2 | Aluminium phosphide | AlP | 2.45 [6] | indirect | |
III-V | 2 | Aluminium arsenide | AlAs | 2.16 [6] | indirect | |
III-V | 2 | Aluminium antimonide | AlSb | 1.6/2.2 [6] | indirect/direct | |
III-V | 2 | Gallium nitride | GaN | 3.44 [5] [6] | direct | Problematic to be doped to p-type, p-doping with Mg and annealing allowed first high-efficiency blue LEDs [3] and blue lasers. Very sensitive to ESD. Insensitive to ionizing radiation. GaN transistors can operate at higher voltages and higher temperatures than GaAs, used in microwave power amplifiers. When doped with e.g. manganese, becomes a magnetic semiconductor. |
III-V | 2 | Gallium phosphide | GaP | 2.26 [5] [6] | indirect | Used in early low to medium brightness cheap red/orange/green LEDs. Used standalone or with GaAsP. Transparent for yellow and red light, used as substrate for GaAsP red/yellow LEDs. Doped with S or Te for n-type, with Zn for p-type. Pure GaP emits green, nitrogen-doped GaP emits yellow-green, ZnO-doped GaP emits red. |
III-V | 2 | Gallium arsenide | GaAs | 1.42 [5] [6] | direct | Second most common in use after silicon, commonly used as substrate for other III-V semiconductors, e.g. InGaAs and GaInNAs. Brittle. Lower hole mobility than Si, P-type CMOS transistors unfeasible. High impurity density, difficult to fabricate small structures. Used for near-IR LEDs, fast electronics, and high-efficiency solar cells. Very similar lattice constant to germanium, can be grown on germanium substrates. |
III-V | 2 | Gallium antimonide | GaSb | 0.73 [5] [6] | direct | Used for infrared detectors and LEDs and thermophotovoltaics. Doped n with Te, p with Zn. |
III-V | 2 | Indium nitride | InN | 0.7 [5] | direct | Possible use in solar cells, but p-type doping difficult. Used frequently as alloys. |
III-V | 2 | Indium phosphide | InP | 1.35 [5] | direct | Commonly used as substrate for epitaxial InGaAs. Superior electron velocity, used in high-power and high-frequency applications. Used in optoelectronics. |
III-V | 2 | Indium arsenide | InAs | 0.36 [5] | direct | Used for infrared detectors for 1–3.8 μm, cooled or uncooled. High electron mobility. InAs dots in InGaAs matrix can serve as quantum dots. Quantum dots may be formed from a monolayer of InAs on InP or GaAs. Strong photo-Dember emitter, used as a terahertz radiation source. |
III-V | 2 | Indium antimonide | InSb | 0.17 [5] | direct | Used in infrared detectors and thermal imaging sensors, high quantum efficiency, low stability, require cooling, used in military long-range thermal imager systems. AlInSb-InSb-AlInSb structure used as quantum well. Very high electron mobility, electron velocity and ballistic length. Transistors can operate below 0.5V and above 200 GHz. Terahertz frequencies maybe achievable. |
II-VI | 2 | Cadmium selenide | CdSe | 1.74 [6] | direct | Nanoparticles used as quantum dots. Intrinsic n-type, difficult to dope p-type, but can be p-type doped with nitrogen. Possible use in optoelectronics. Tested for high-efficiency solar cells. |
II-VI | 2 | Cadmium sulfide | CdS | 2.42 [6] | direct | Used in photoresistors and solar cells; CdS/Cu2S was the first efficient solar cell. Used in solar cells with CdTe. Common as quantum dots. Crystals can act as solid-state lasers. Electroluminescent. When doped, can act as a phosphor. |
II-VI | 2 | Cadmium telluride | CdTe | 1.49 [6] | direct | Used in solar cells with CdS. Used in thin film solar cells and other cadmium telluride photovoltaics; less efficient than crystalline silicon but cheaper. High electro-optic effect, used in electro-optic modulators. Fluorescent at 790 nm. Nanoparticles usable as quantum dots. |
II-VI, oxide | 2 | Zinc oxide | ZnO | 3.37 [6] | direct | Photocatalytic. Band gap is tunable from 3 to 4 eV by alloying with magnesium oxide and cadmium oxide. Intrinsic n-type, p-type doping is difficult. Heavy aluminium, indium, or gallium doping yields transparent conductive coatings; ZnO:Al is used as window coatings transparent in visible and reflective in infrared region and as conductive films in LCD displays and solar panels as a replacement of indium tin oxide. Resistant to radiation damage. Possible use in LEDs and laser diodes. Possible use in random lasers. |
II-VI | 2 | Zinc selenide | ZnSe | 2.7 [6] | direct | Used for blue lasers and LEDs. Easy to n-type doping, p-type doping is difficult but can be done with e.g. nitrogen. Common optical material in infrared optics. |
II-VI | 2 | Zinc sulfide | ZnS | 3.54/3.91 [6] | direct | Band gap 3.54 eV (cubic), 3.91 (hexagonal). Can be doped both n-type and p-type. Common scintillator/phosphor when suitably doped. |
II-VI | 2 | Zinc telluride | ZnTe | 2.3 [6] | direct | Can be grown on AlSb, GaSb, InAs, and PbSe. Used in solar cells, components of microwave generators, blue LEDs and lasers. Used in electrooptics. Together with lithium niobate used to generate terahertz radiation. |
I-VII | 2 | Cuprous chloride | CuCl | 3.4 [21] | direct | |
I-VI | 2 | Copper(I) sulfide | Cu2S | 1.2 [20] | indirect | p-type, Cu2S/CdS was the first efficient thin film solar cell |
IV-VI | 2 | Lead selenide | PbSe | 0.26 [17] | direct | Used in infrared detectors for thermal imaging. Nanocrystals usable as quantum dots. Good high temperature thermoelectric material. |
IV-VI | 2 | Lead(II) sulfide | PbS | 0.37 [22] | Mineral galena, first semiconductor in practical use, used in cat's whisker detectors; the detectors are slow due to high dielectric constant of PbS. Oldest material used in infrared detectors. At room temperature can detect SWIR, longer wavelengths require cooling. | |
IV-VI | 2 | Lead telluride | PbTe | 0.32 [5] | Low thermal conductivity, good thermoelectric material at elevated temperature for thermoelectric generators. | |
IV-VI | 2 | Tin(II) sulfide | SnS | 1.3/1.0 [23] | direct/indirect | Tin sulfide (SnS) is a semiconductor with direct optical band gap of 1.3 eV and absorption coefficient above 104 cm−1 for photon energies above 1.3 eV. It is a p-type semiconductor whose electrical properties can be tailored by doping and structural modification and has emerged as one of the simple, non-toxic and affordable material for thin films solar cells since a decade. |
IV-VI | 2 | Tin(IV) sulfide | SnS2 | 2.2 [24] | SnS2 is widely used in gas sensing applications. | |
IV-VI | 2 | Tin telluride | SnTe | 0.18 | direct | Complex band structure. |
V-VI, layered | 2 | Bismuth telluride | Bi2Te3 | 0.13 [5] | Efficient thermoelectric material near room temperature when alloyed with selenium or antimony. Narrow-gap layered semiconductor. High electrical conductivity, low thermal conductivity. Topological insulator. | |
II-V | 2 | Cadmium phosphide | Cd3P2 | 0.5 [25] | ||
II-V | 2 | Cadmium arsenide | Cd3As2 | 0 | N-type intrinsic semiconductor. Very high electron mobility. Used in infrared detectors, photodetectors, dynamic thin-film pressure sensors, and magnetoresistors. Recent measurements suggest that 3D Cd3As2 is actually a zero band-gap Dirac semimetal in which electrons behave relativistically as in graphene. [26] | |
II-V | 2 | Zinc phosphide | Zn3P2 | 1.5 [27] | direct | Usually p-type. |
II-V | 2 | Zinc diphosphide | ZnP2 | 2.1 [28] | ||
II-V | 2 | Zinc arsenide | Zn3As2 | 1.0 [29] | The lowest direct and indirect bandgaps are within 30 meV or each other. [29] | |
II-V | 2 | Zinc antimonide | Zn3Sb2 | Used in infrared detectors and thermal imagers, transistors, and magnetoresistors. | ||
Oxide | 2 | Titanium dioxide, anatase | TiO2 | 3.20 [30] | indirect | Photocatalytic, n-type |
Oxide | 2 | Titanium dioxide, rutile | TiO2 | 3.0 [30] | direct | Photocatalytic, n-type |
Oxide | 2 | Titanium dioxide, brookite | TiO2 | 3.26 [30] | [31] | |
Oxide | 2 | Copper(I) oxide | Cu2O | 2.17 [32] | One of the most studied semiconductors. Many applications and effects first demonstrated with it. Formerly used in rectifier diodes, before silicon. | |
Oxide | 2 | Copper(II) oxide | CuO | 1.2 | N-type semiconductor. [33] | |
Oxide | 2 | Uranium dioxide | UO2 | 1.3 | High Seebeck coefficient, resistant to high temperatures, promising thermoelectric and thermophotovoltaic applications. Formerly used in URDOX resistors, conducting at high temperature. Resistant to radiation damage. | |
Oxide | 2 | Tin dioxide | SnO2 | 3.7 | Oxygen-deficient n-type semiconductor. Used in gas sensors. | |
Oxide | 3 | Barium titanate | BaTiO3 | 3 | Ferroelectric, piezoelectric. Used in some uncooled thermal imagers. Used in nonlinear optics. | |
Oxide | 3 | Strontium titanate | SrTiO3 | 3.3 | Ferroelectric, piezoelectric. Used in varistors. Conductive when niobium-doped. | |
Oxide | 3 | Lithium niobate | LiNbO3 | 4 | Ferroelectric, piezoelectric, shows Pockels effect. Wide uses in electrooptics and photonics. | |
Oxide, V-VI | 2 | monoclinic Vanadium(IV) oxide | VO2 | 0.7 [34] | optical | Stable below 67 °C |
Layered | 2 | Lead(II) iodide | PbI2 | 2.4 [35] | PbI2 is a layered direct bandgap semiconductor with bandgap of 2.4 eV in its bulk form, whereas its 2D monolayer has an indirect bandgap of ~2.5 eV, with possibilities to tune the bandgap between 1–3 eV | |
Layered | 2 | Molybdenum disulfide | MoS2 | 1.23 eV (2H) [36] | indirect | |
Layered | 2 | Gallium selenide | GaSe | 2.1 | indirect | Photoconductor. Uses in nonlinear optics. Used as 2D-material. Air sensitive. [37] [38] [39] |
Layered | 2 | Indium selenide | InSe | 1.26–2.35 eV [39] | direct (indirect in 2D) | Air sensitive. High electrical mobility in few- and mono-layer form. [37] [38] [39] |
Layered | 2 | Tin sulfide | SnS | >1.5 eV | direct | |
Layered | 2 | Bismuth sulfide | Bi2S3 | 1.3 [5] | ||
Magnetic, diluted (DMS) [40] | 3 | Gallium manganese arsenide | GaMnAs | |||
Magnetic, diluted (DMS) | 3 | Lead manganese telluride | PbMnTe | |||
Magnetic | 4 | Lanthanum calcium manganate | La0.7Ca0.3MnO3 | Colossal magnetoresistance | ||
Magnetic | 2 | Iron(II) oxide | FeO | 2.2 [41] | Antiferromagnetic. Band gap for iron oxide nanoparticles was found to be 2.2 eV and on doping the band gap found to be increased up to 2.5 eV | |
Magnetic | 2 | Nickel(II) oxide | NiO | 3.6–4.0 | direct [42] [43] | Antiferromagnetic |
Magnetic | 2 | Europium(II) oxide | EuO | Ferromagnetic | ||
Magnetic | 2 | Europium(II) sulfide | EuS | Ferromagnetic | ||
Magnetic | 2 | Chromium(III) bromide | CrBr3 | |||
other | 3 | Copper indium selenide, CIS | CuInSe2 | 1 | direct | |
other | 3 | Silver gallium sulfide | AgGaS2 | Nonlinear optical properties | ||
other | 3 | Zinc silicon phosphide | ZnSiP2 | 2.0 [20] | ||
other | 2 | Arsenic trisulfide Orpiment | As2S3 | 2.7 [44] | direct | Semiconductive in both crystalline and glassy state |
other | 2 | Arsenic sulfide Realgar | As4S4 | Semiconductive in both crystalline and glassy state | ||
other | 2 | Platinum silicide | PtSi | Used in infrared detectors for 1–5 μm. Used in infrared astronomy. High stability, low drift, used for measurements. Low quantum efficiency. | ||
other | 2 | Bismuth(III) iodide | BiI3 | |||
other | 2 | Mercury(II) iodide | HgI2 | Used in some gamma-ray and x-ray detectors and imaging systems operating at room temperature. | ||
other | 2 | Thallium(I) bromide | TlBr | 2.68 [45] | Used in some gamma-ray and x-ray detectors and imaging systems operating at room temperature. Used as a real-time x-ray image sensor. | |
other | 2 | Silver sulfide | Ag2S | 0.9 [46] | ||
other | 2 | Iron disulfide | FeS2 | 0.95 [47] | Mineral pyrite. Used in later cat's whisker detectors, investigated for solar cells. | |
other | 4 | Copper zinc tin sulfide, CZTS | Cu2ZnSnS4 | 1.49 | direct | Cu2ZnSnS4 is derived from CIGS, replacing the Indium/Gallium with earth abundant Zinc/Tin. |
other | 4 | Copper zinc antimony sulfide, CZAS | Cu1.18Zn0.40Sb1.90S7.2 | 2.2 [48] | direct | Copper zinc antimony sulfide is derived from copper antimony sulfide (CAS), a famatinite class of compound. |
other | 3 | Copper tin sulfide, CTS | Cu2SnS3 | 0.91 [20] | direct | Cu2SnS3 is p-type semiconductor and it can be used in thin film solar cell application. |
The following semiconducting systems can be tuned to some extent, and represent not a single material but a class of materials.
Group | Elem. | Material class | Formula | Band gap (eV) | Gap type | Description | |
---|---|---|---|---|---|---|---|
Lower | Upper | ||||||
IV-VI | 3 | Lead tin telluride | Pb1−xSnxTe | 0 | 0.29 | Used in infrared detectors and for thermal imaging | |
IV | 2 | Silicon-germanium | Si1−xGex | 0.67 | 1.11 [5] | direct/indirect | Adjustable band gap, allows construction of heterojunction structures. Certain thicknesses of superlattices have direct band gap. [49] |
IV | 2 | Silicon-tin | Si1−xSnx | 1.0 | 1.11 | indirect | Adjustable band gap. [50] |
III-V | 3 | Aluminium gallium arsenide | AlxGa1−xAs | 1.42 | 2.16 [5] | direct/indirect | Direct band gap for x<0.4 (corresponding to 1.42–1.95 eV); can be lattice-matched to GaAs substrate over entire composition range; tends to oxidize; n-doping with Si, Se, Te; p-doping with Zn, C, Be, Mg. [3] Can be used for infrared laser diodes. Used as a barrier layer in GaAs devices to confine electrons to GaAs (see e.g. QWIP). AlGaAs with composition close to AlAs is almost transparent to sunlight. Used in GaAs/AlGaAs solar cells. |
III-V | 3 | Indium gallium arsenide | InxGa1−xAs | 0.36 | 1.43 | direct | Well-developed material. Can be lattice matched to InP substrates. Use in infrared technology and thermophotovoltaics. Indium content determines charge carrier density. For x=0.015, InGaAs perfectly lattice-matches germanium; can be used in multijunction photovoltaic cells. Used in infrared sensors, avalanche photodiodes, laser diodes, optical fiber communication detectors, and short-wavelength infrared cameras. |
III-V | 3 | Indium gallium phosphide | InxGa1−xP | 1.35 | 2.26 | direct/indirect | Used for HEMT and HBT structures and high-efficiency multijunction solar cells for e.g. satellites. Ga0.5In0.5P is almost lattice-matched to GaAs, with AlGaIn used for quantum wells for red lasers. |
III-V | 3 | Aluminium indium arsenide | AlxIn1−xAs | 0.36 | 2.16 | direct/indirect | Buffer layer in metamorphic HEMT transistors, adjusting lattice constant between GaAs substrate and GaInAs channel. Can form layered heterostructures acting as quantum wells, in e.g. quantum cascade lasers. |
III-V | 3 | Aluminium gallium antimonide | AlxGa1−xSb | 0.7 | 1.61 | direct/indirect | Used in HBTs, HEMTs, resonant-tunneling diodes and some niche optoelectronics. Also used as a buffer layer for InAs quantum wells. |
III-V | 3 | Aluminium indium antimonide | AlxIn1−xSb | 0.17 | 1.61 | direct/indirect | Used as a buffer layer in InSb-based quantum wells and other devices grown on GaAs and GaSb substrates. Also used as the active layer in some mid-infrared LEDs and photodiodes. |
III-V | 3 | Gallium arsenide nitride | GaAsN | ||||
III-V | 3 | Gallium arsenide phosphide | GaAsP | 1.43 | 2.26 | direct/indirect | Used in red, orange and yellow LEDs. Often grown on GaP. Can be doped with nitrogen. |
III-V | 3 | Aluminium arsenide antimonide | AlAsSb | 1.61 | 2.16 | indirect | Used as a barrier layer in infrared photodetectors. Can be lattice matched to GaSb, InAs and InP. |
III-V | 3 | Gallium arsenide antimonide | GaAsSb | 0.7 | 1.42 [5] | direct | Used in HBTs and in tunnel junctions in multi-junction solar cells. GaAs0.51Sb0.49 is lattice matched to InP. |
III-V | 3 | Aluminium gallium nitride | AlGaN | 3.44 | 6.28 | direct | Used in blue laser diodes, ultraviolet LEDs (down to 250 nm), and AlGaN/GaN HEMTs. Can be grown on sapphire. Used in heterojunctions with AlN and GaN. |
III-V | 3 | Aluminium gallium phosphide | AlGaP | 2.26 | 2.45 | indirect | Used in some green LEDs. |
III-V | 3 | Indium gallium nitride | InGaN | 2 | 3.4 | direct | InxGa1–xN, x usually between 0.02 and 0.3 (0.02 for near-UV, 0.1 for 390 nm, 0.2 for 420 nm, 0.3 for 440 nm). Can be grown epitaxially on sapphire, SiC wafers or silicon. Used in modern blue and green LEDs, InGaN quantum wells are effective emitters from green to ultraviolet. Insensitive to radiation damage, possible use in satellite solar cells. Insensitive to defects, tolerant to lattice mismatch damage. High heat capacity. |
III-V | 3 | Indium arsenide antimonide | InAsSb | 0.17 | 0.36 | direct | Primarily used in mid- and long-wave infrared photodetectors due to its small bandgap, which reaches a minimum of around 0.08 eV in InAs0.4Sb0.6 at room temperature. |
III-V | 3 | Indium gallium antimonide | InGaSb | 0.17 | 0.7 | direct | Used in some transistors and infrared photodetectors. |
III-V | 4 | Aluminium gallium indium phosphide | AlGaInP | direct/indirect | Also InAlGaP, InGaAlP, AlInGaP; for lattice matching to GaAs substrates the In mole fraction is fixed at about 0.48, the Al/Ga ratio is adjusted to achieve band gaps between about 1.9 and 2.35 eV; direct or indirect band gaps depending on the Al/Ga/In ratios; used for waveengths between 560 and 650 nm; tends to form ordered phases during deposition, which has to be prevented [3] | ||
III-V | 4 | Aluminium gallium arsenide phosphide | AlGaAsP | ||||
III-V | 4 | Indium gallium arsenide phosphide | InGaAsP | ||||
III-V | 4 | Indium gallium arsenide antimonide | InGaAsSb | Use in thermophotovoltaics. | |||
III-V | 4 | Indium arsenide antimonide phosphide | InAsSbP | Use in thermophotovoltaics. | |||
III-V | 4 | Aluminium indium arsenide phosphide | AlInAsP | ||||
III-V | 4 | Aluminium gallium arsenide nitride | AlGaAsN | ||||
III-V | 4 | Indium gallium arsenide nitride | InGaAsN | ||||
III-V | 4 | Indium aluminium arsenide nitride | InAlAsN | ||||
III-V | 4 | Gallium arsenide antimonide nitride | GaAsSbN | ||||
III-V | 5 | Gallium indium nitride arsenide antimonide | GaInNAsSb | ||||
III-V | 5 | Gallium indium arsenide antimonide phosphide | GaInAsSbP | Can be grown on InAs, GaSb, and other substrates. Can be lattice matched by varying composition. Possibly usable for mid-infrared LEDs. | |||
II-VI | 3 | Cadmium zinc telluride, CZT | CdZnTe | 1.4 | 2.2 | direct | Efficient solid-state x-ray and gamma-ray detector, can operate at room temperature. High electro-optic coefficient. Used in solar cells. Can be used to generate and detect terahertz radiation. Can be used as a substrate for epitaxial growth of HgCdTe. |
II-VI | 3 | Mercury cadmium telluride | HgCdTe | 0 | 1.5 | Known as "MerCad". Extensive use in sensitive cooled infrared imaging sensors, infrared astronomy, and infrared detectors. Alloy of mercury telluride (a semimetal, zero band gap) and CdTe. High electron mobility. The only common material capable of operating in both 3–5 μm and 12–15 μm atmospheric windows. Can be grown on CdZnTe. | |
II-VI | 3 | Mercury zinc telluride | HgZnTe | 0 | 2.25 | Used in infrared detectors, infrared imaging sensors, and infrared astronomy. Better mechanical and thermal properties than HgCdTe but more difficult to control the composition. More difficult to form complex heterostructures. | |
II-VI | 3 | Mercury zinc selenide | HgZnSe | ||||
II-V | 4 | Zinc cadmium phosphide arsenide | (Zn1−xCdx)3(P1−yAsy)2 [51] | 0 [26] | 1.5 [52] | Various applications in optoelectronics (incl. photovoltaics), electronics and thermoelectrics. [53] | |
other | 4 | Copper indium gallium selenide, CIGS | Cu(In,Ga)Se2 | 1 | 1.7 | direct | CuInxGa1–xSe2. Polycrystalline. Used in thin film solar cells. |
A semiconductor is a material that has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity generally falls as its temperature rises; metals behave in the opposite way. In many cases their conducting properties may be altered in useful ways by introducing impurities ("doping") into the crystal structure. When two differently doped regions exist in the same crystal, a semiconductor junction is created. The behavior of charge carriers, which include electrons, ions, and electron holes, at these junctions is the basis of diodes, transistors, and most modern electronics. Some examples of semiconductors are silicon, germanium, gallium arsenide, and elements near the so-called "metalloid staircase" on the periodic table. After silicon, gallium arsenide is the second-most common semiconductor and is used in laser diodes, solar cells, microwave-frequency integrated circuits, and others. Silicon is a critical element for fabricating most electronic circuits.
In solid-state physics and solid-state chemistry, a band gap, also called a bandgap or energy gap, is an energy range in a solid where no electronic states exist. In graphs of the electronic band structure of solids, the band gap refers to the energy difference between the top of the valence band and the bottom of the conduction band in insulators and semiconductors. It is the energy required to promote an electron from the valence band to the conduction band. The resulting conduction-band electron are free to move within the crystal lattice and serve as charge carriers to conduct electric current. It is closely related to the HOMO/LUMO gap in chemistry. If the valence band is completely full and the conduction band is completely empty, then electrons cannot move within the solid because there are no available states. If the electrons are not free to move within the crystal lattice, then there is no generated current due to no net charge carrier mobility. However, if some electrons transfer from the valence band to the conduction band, then current can flow. Therefore, the band gap is a major factor determining the electrical conductivity of a solid. Substances having large band gaps are generally insulators, those with small band gaps are semiconductor, and conductors either have very small band gaps or none, because the valence and conduction bands overlap to form a continuous band.
Gallium arsenide (GaAs) is a III-V direct band gap semiconductor with a zinc blende crystal structure.
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 epitaxial film or epitaxial layer. The relative orientation(s) of the epitaxial layer to the seed layer is defined in terms of the orientation of the crystal lattice of each material. For most epitaxial growths, the new layer is usually crystalline and each crystallographic domain of the overlayer must have a well-defined orientation relative to the substrate crystal structure. Epitaxy can involve single-crystal structures, although grain-to-grain epitaxy has been observed in granular films. For most technological applications, single-domain epitaxy, which is the growth of an overlayer crystal with one well-defined orientation with respect to the substrate crystal, is preferred. Epitaxy can also play an important role while growing superlattice structures.
Wide-bandgap semiconductors are semiconductor materials which have a larger band gap than conventional semiconductors. Conventional semiconductors like silicon have a bandgap in the range of 0.6 – 1.5 electronvolt (eV), whereas wide-bandgap materials have bandgaps in the range above 2 eV. Generally, wide-bandgap semiconductors have electronic properties which fall in between those of conventional semiconductors and insulators.
Gallium nitride is a binary III/V direct bandgap semiconductor commonly used in blue light-emitting diodes since the 1990s. The compound is a very hard material that has a Wurtzite crystal structure. Its wide band gap of 3.4 eV affords it special properties for applications in optoelectronic, high-power and high-frequency devices. For example, GaN is the substrate that makes violet (405 nm) laser diodes possible, without requiring nonlinear optical frequency doubling.
Indium phosphide (InP) is a binary semiconductor composed of indium and phosphorus. It has a face-centered cubic ("zincblende") crystal structure, identical to that of GaAs and most of the III-V semiconductors.
In semiconductor production, doping is the intentional introduction of impurities into an intrinsic (undoped) semiconductor for the purpose of modulating its electrical, optical and structural properties. The doped material is referred to as an extrinsic semiconductor.
Magnetic semiconductors are semiconductor materials that exhibit both ferromagnetism and useful semiconductor properties. If implemented in devices, these materials could provide a new type of control of conduction. Whereas traditional electronics are based on control of charge carriers, practical magnetic semiconductors would also allow control of quantum spin state. This would theoretically provide near-total spin polarization, which is an important property for spintronics applications, e.g. spin transistors.
Indium gallium arsenide (InGaAs) is a ternary alloy of indium arsenide (InAs) and gallium arsenide (GaAs). Indium and gallium are group III elements of the periodic table while arsenic is a group V element. Alloys made of these chemical groups are referred to as "III-V" compounds. InGaAs has properties intermediate between those of GaAs and InAs. InGaAs is a room-temperature semiconductor with applications in electronics and photonics.
Indium gallium nitride is a semiconductor material made of a mix of gallium nitride (GaN) and indium nitride (InN). It is a ternary group III/group V direct bandgap semiconductor. Its bandgap can be tuned by varying the amount of indium in the alloy. InxGa1−xN has a direct bandgap span from the infrared for InN to the ultraviolet of GaN. The ratio of In/Ga is usually between 0.02/0.98 and 0.3/0.7.
Gallium phosphide (GaP), a phosphide of gallium, is a compound semiconductor material with an indirect band gap of 2.24 eV at room temperature. Impure polycrystalline material has the appearance of pale orange or grayish pieces. Undoped single crystals are orange, but strongly doped wafers appear darker due to free-carrier absorption. It is odorless and insoluble in water.
Gallium antimonide (GaSb) is a semiconducting compound of gallium and antimony of the III-V family. It has a room temperature lattice constant of about 0.610 nm. It has a room temperature direct bandgap of approximately 0.73 eV.
Boron arsenide is a chemical compound involving boron and arsenic, usually with a chemical formula BAs. Other boron arsenide compounds are known, such as the subarsenide B12As2. Chemical synthesis of cubic BAs is very challenging and its single crystal forms usually have defects.
Indium(III) oxide (In2O3) is a chemical compound, an amphoteric oxide of indium.
Sorab (Soli) K. Ghandhi was a professor Emeritus at Rensselaer Polytechnic Institute (RPI) known for his pioneering work in electrical engineering and microelectronics education, and in the research and development of Organometallic Vapor Phase Epitaxy (OMVPE) for compound semiconductors. He was the recipient of the IEEE Education Award "For pioneering contributions to semiconductor and microelectronics education" in 2010.
Rubin Braunstein (1922–2018) was an American physicist and educator. In 1955 he published the first measurements of light emission by semiconductor diodes made from crystals of gallium arsenide (GaAs), gallium antimonide (GaSb), and indium phosphide (InP). GaAs, GaSb, and InP are examples of III-V semiconductors. The III-V semiconductors absorb and emit light much more strongly than silicon, which is the best-known semiconductor. Braunstein's devices are the forerunners of contemporary LED lighting and semiconductor lasers, which typically employ III-V semiconductors. The 2000 and 2014 Nobel Prizes in Physics were awarded for further advances in closely related fields.
Aluminium indium antimonide, also known as indium aluminium antimonide or AlInSb (AlxIn1-xSb), is a ternary III-V semiconductor compound. It can be considered as an alloy between aluminium antimonide and indium antimonide. The alloy can contain any ratio between aluminium and indium. AlInSb refers generally to any composition of the alloy.
Gallium arsenide antimonide, also known as gallium antimonide arsenide or GaAsSb, is a ternary III-V semiconductor compound; x indicates the fractions of arsenic and antimony in the alloy. GaAsSb refers generally to any composition of the alloy. It is an alloy of gallium arsenide (GaAs) and gallium antimonide (GaSb).
Gallium indium antimonide, also known as indium gallium antimonide, GaInSb, or InGaSb (GaxIn1-xSb), is a ternary III-V semiconductor compound. It can be considered as an alloy between gallium antimonide and indium antimonide. The alloy can contain any ratio between gallium and indium. GaInSb refers generally to any composition of the alloy.