List of semiconductor materials
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 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 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 can not be created by just growing an oxide layer; GaAs is therefore used only where silicon is not sufficient.
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.
Types of semiconductor materials
- Group IV elemental semiconductors,
- Group IV compound semiconductors
- Group VI elemental semiconductors,
- III–V semiconductors: Crystallizing with high degree of stoichiometry, most can be obtained as both n-type and p-type. Many have high carrier mobilities and direct energy gaps, making them useful for optoelectronics.
- II–VI semiconductors: usually p-type, except ZnTe and ZnO which is n-type
- I–VII semiconductors
- IV–VI semiconductors
- V–VI semiconductors
- II–V semiconductors
- I-III-VI2 semiconductors
- Oxides
- Layered semiconductors
- Magnetic semiconductors
- Organic semiconductors
- Charge-transfer complexes
- Others
Compound semiconductors
Fabrication
is the most popular deposition technology for the formation of compound semiconducting thin films for devices. It uses ultrapure metalorganics and/or hydrides as precursor source materials in an ambient gas such as hydrogen.Other techniques of choice include:
- Molecular beam epitaxy
- Hydride vapour phase epitaxy
- Liquid phase epitaxy
- Metal-organic molecular beam epitaxy
- Atomic layer deposition
Table of semiconductor materials
Table of semiconductor alloy systems
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 lower | upper | Gap type | Description |
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 | indirect | adjustable band gap, allows construction of heterojunction structures. Certain thicknesses of superlattices have direct band gap. |
IV | 2 | Silicon-tin | Si1−xSnx | 1.0 | 1.11 | indirect | Adjustable band gap. |
III-V | 3 | Aluminium gallium arsenide | AlxGa1−xAs | 1.42 | 2.16 | direct/indirect | direct band gap for x<0.4 ; 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. Can be used for infrared laser diodes. Used as a barrier layer in GaAs devices to confine electrons to GaAs. 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 indium antimonide | AlxIn1−xSb | ||||
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 | direct | |
III-V | 3 | Aluminium gallium nitride | AlGaN | 3.44 | 6.28 | direct | Used in blue laser diodes, ultraviolet LEDs, 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. 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 | ||
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 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 | ||||
other | 4 | Copper indium gallium selenide, CIGS | CuSe2 | 1 | 1.7 | direct | CuInxGa1–xSe2. Polycrystalline. Used in thin film solar cells. |