Semiconductor materials are nominally small band gap insulators. The defining property of a semiconductor material is that it can be doped with impurities that alter its electronic properties in a controllable way.
Because of their application in devices like transistors (and therefore computers) and lasers, 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, and allowing e.g. matching to wavelengths with lowest losses in 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 can not be created by just growing an oxide layer; GaAs is therefore used only where silicon is not sufficient.[1]
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.[2]
Contents |
Group | Elem. | Material | Formula | Band gap (eV) | Gap type | Description |
---|---|---|---|---|---|---|
IV | 1 | Diamond | C | 5.47[3][4] | indirect | Excellent thermal conductivity. |
IV | 1 | Silicon | Si | 1.11[3][4] | indirect | Most common semiconductor, easy to fabricate. Good electrical and mechanical properties. |
IV | 1 | Germanium | Ge | 0.67[3][4] | 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 | 2 | Silicon carbide, 3C-SiC | SiC | 2.3[3] | indirect | used for early yellow LEDs |
IV | 2 | Silicon carbide, 4H-SiC | SiC | 3.3[3] | indirect | |
IV | 2 | Silicon carbide, 6H-SiC | SiC | 3.0[3] | indirect | used for early blue LEDs |
IV | 2 | Silicon-germanium | SiGe | 0.67–1.11[3] | indirect | adjustable band gap, allows construction of heterojunction structures. Certain thicknesses of superlattices have direct band gap.[5] |
III-V | 2 | Aluminium antimonide | AlSb | 1.6/2.2[4] | indirect/direct | |
III-V | 2 | Aluminium arsenide | AlAs | 2.16[4] | indirect | |
III-V | 2 | Aluminium nitride | AlN | 6.28[3] | 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[4] | indirect | |
III-V | 2 | Boron nitride, cubic | BN | 6.36[6] | indirect | potentially useful for ultraviolet LEDs |
III-V | 2 | Boron nitride, hexagonal | BN | 5.96[6] | quasi-direct | potentially useful for ultraviolet LEDs |
III-V | 2 | Boron nitride, nanotube | BN | ~5.5 | ||
III-V | 2 | Boron phosphide | BP | 2 | indirect | |
III-V | 2 | Boron arsenide | BAs | 1.5 | indirect | 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 | Gallium antimonide | GaSb | 0.726[3][4] | direct | Used for infrared detectors and LEDs and thermophotovoltaics. Doped n with Te, p with Zn. |
III-V | 2 | Gallium arsenide | GaAs | 1.43[3][4] | 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 nitride | GaN | 3.44[3][4] | direct | problematic to be doped to p-type, p-doping with Mg and annealing allowed first high-efficiency blue LEDs[2] and blue lasers. Very sensitive to ESD. Insensitive to ionizing radiation, suitable for spacecraft solar panels. 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[3][4] | 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 | Indium antimonide | InSb | 0.17[3] | 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. |
III-V | 2 | Indium arsenide | InAs | 0.36[3] | 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 nitride | InN | 0.7[3] | direct | Possible use in solar cells, but p-type doping difficult. Used frequently as alloys. |
III-V | 2 | Indium phosphide | InP | 1.35[3] | direct | Commonly used as substrate for epitaxial InGaAs. Superior electron veloxity, used in high-power and high-frequency applications. Used in optoelectronics. |
III-V | 3 | Aluminium gallium arsenide | AlGaAs | 1.42–2.16[3] | direct/indirect | AlxGa1–xAs, 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.[2] 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 | InGaAs | 0.36–1.43 | direct | InxGa1–xAs. 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 | InGaP | 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 | AlInAs | 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 indium antimonide | AlInSb | |||
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 | Gallium arsenide antimonide | GaAsSb | 0.7–1.42[3] | direct | |
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 0.02–0.3 (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 | |||
III-V | 3 | Indium gallium antimonide | InGaSb | |||
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 560–650 nm; tends to form ordered phases during deposition, which has to be prevented[2] | |
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 | 2 | Cadmium selenide | CdSe | 1.74[4] | 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[4] | 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[4] | Used in solar cells with CdS. Used in thin film solar cells and other cadmium telluride photovoltaics; less efficient than polysilicon 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[4] | direct | Photocatalytic. Bandwidth 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[4] | 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[4] | 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 | 2.25[4] | direct | Can be grown on AlSb, GaSb, InAs, and PbSe. Used in solar cells, compoments of microwave generators, blue LEDs and lasers. Used in electrooptics. Together with lithium niobate used to generate terahertz radiation. |
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 | |||
I-VII | 2 | Cuprous chloride | CuCl | 3.4[7] | direct | |
I-VI | 2 | Copper sulfide | Cu2S | 1.2 | direct | p-type, Cu2S/CdS was the first efficient thin film solar cell |
IV-VI | 2 | Lead selenide | PbSe | 0.27 | direct | Used in infrared detectors for thermal imaging. Nanocrystals usable as quantum dots. |
IV-VI | 2 | Lead(II) sulfide | PbS | 0.37 | 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 | Low thermal conductivity, good thermoelectric material. | |
IV-VI | 2 | Tin sulfide | SnS | 1.0 | indirect | |
IV-VI | 2 | Tin sulfide | SnS2 | 2.2 | ||
IV-VI | 2 | Tin telluride | SnTe | Complex band structure. | ||
IV-VI | 3 | Lead tin telluride | PbSnTe | Used in infrared detectors and for thermal imaging. | ||
IV-VI | 3 | Thallium tin telluride | Tl2SnTe5 | |||
IV-VI | 3 | Thallium germanium telluride | Tl2GeTe5 | |||
V-VI, layered | 2 | Bismuth telluride | Bi2Te3 | Efficient thermoelectric material when alloyed with selenium or antimony. Narrow-gap layered semiconductor. High electrical conductivity, low thermal conductivity. | ||
II-V | 2 | Cadmium phosphide | Cd3P2 | |||
II-V | 2 | Cadmium arsenide | Cd3As2 | 0.14 | N-type intrinsic semiconductor. Very high electron mobility. Used in infrared detectors, photodetectors, dynamic thin-film pressure sensors, and magnetoresistors. | |
II-V | 2 | Cadmium antimonide | Cd3Sb2 | |||
II-V | 2 | Zinc phosphide | Zn3P2 | |||
II-V | 2 | Zinc arsenide | Zn3As2 | |||
II-V | 2 | Zinc antimonide | Zn3Sb2 | Used in infrared detectors and thermal imagers, transistors, and magnetoresistors. | ||
Oxide | 2 | Titanium dioxide, anatase | TiO2 | 3.2 | photocatalytic | |
Oxide | 2 | Titanium dioxide, rutile | TiO2 | 3.02 | photocatalytic | |
Oxide | 2 | Titanium dioxide, brookite | TiO2 | 2.96 | [8] | |
Oxide | 2 | Copper(I) oxide | Cu2O | 2.17 [9] | 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 | P-type semiconductor. | |
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 | Uranium trioxide | UO3 | |||
Oxide | 2 | Bismuth trioxide | Bi2O3 | Ionic conductor, applications in fuel cells. | ||
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 | 3 | Lanthanum copper oxide | La2CuO4 | 2 | superconductive when doped with barium or strontium | |
Layered | 2 | Lead(II) iodide | PbI2 | |||
Layered | 2 | Molybdenum disulfide | MoS2 | |||
Layered | 2 | Gallium selenide | GaSe | 2.1 | indirect | Photoconductor. Uses in nonlinear optics. |
Layered | 2 | Tin sulfide | SnS | |||
Layered | 2 | Bismuth sulfide | Bi2S3 | |||
Magnetic, diluted (DMS)[10] | 3 | Gallium manganese arsenide | GaMnAs | |||
Magnetic, diluted (DMS) | 3 | Indium manganese arsenide | InMnAs | |||
Magnetic, diluted (DMS) | 3 | Cadmium manganese telluride | CdMnTe | |||
Magnetic, diluted (DMS) | 3 | Lead manganese telluride | PbMnTe | |||
Magnetic | 4 | Lanthanum calcium manganate | La0.7Ca0.3MnO3 | colossal magnetoresistance | ||
Magnetic | 2 | Iron(II) oxide | FeO | antiferromagnetic | ||
Magnetic | 2 | Nickel(II) oxide | NiO | antiferromagnetic | ||
Magnetic | 2 | Europium(II) oxide | EuO | ferromagnetic | ||
Magnetic | 2 | Europium(II) sulfide | EuS | ferromagnetic | ||
Magnetic | 2 | Chromium(III) bromide | CrBr3 | |||
other | 4 | Copper indium gallium selenide, CIGS | Cu(In,Ga)Se2 | 1–1.7 | direct | CuInxGa1–xSe2. Polycrystalline. Used in thin film solar cells, highly efficient. |
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 | 3 | Copper indium selenide, CIS | CuInSe2 | 1 | direct | |
other | 3 | Silver gallium sulfide | AgGaS2 | nonlinear optical properties | ||
other | 3 | Zinc silicon phosphide | ZnSiP2 | |||
other | 2 | Arsenic selenide | As2S3 | 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 | 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 | 1 | Selenium | Se | 1.74 | Used in selenium rectifiers. | |
other | 2 | Silver sulfide | Ag2S | 0.9 [11] | ||
other | 2 | Iron disulfide | FeS2 | 0.95 | Mineral pyrite. Used in later cat's whisker detectors, investigated for solar cells. |