Boron arsenide is a chemical compound involving

boron Boron is a chemical element with the symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the '' boron group'' it has t ...

and

arsenic Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, b ...

, usually with a

chemical formula In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, ...

BAs. Other boron arsenide compounds are known, such as the subarsenide . Chemical synthesis of cubic BAs is very challenging and its single crystal forms usually have defects.

Properties

BAs is a cubic (

sphalerite Sphalerite (sometimes spelled sphaelerite) is a sulfide mineral with the chemical formula . It is the most important ore of zinc. Sphalerite is found in a variety of deposit types, but it is primarily in sedimentary exhalative, Mississippi-V ...

)

semiconductor A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way ...

in the

III-V 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. Because o ...

family with a

lattice constant A lattice constant or lattice parameter is one of the physical dimensions and angles that determine the geometry of the unit cells in a crystal lattice, and is proportional to the distance between atoms in the crystal. A simple cubic crystal has o ...

of 0.4777 nm and an

indirect band gap In semiconductor physics, the band gap of a semiconductor can be of two basic types, a direct band gap or an indirect band gap. The minimal-energy state in the conduction band and the maximal-energy state in the valence band are each characterize ...

of 1.82 eV. Cubic BAs is reported to decompose to the subarsenide B₁₂As₂ at temperatures above 920 °C. Boron arsenide has a melting point of 2076 °C. The thermal conductivity of BAs is very high: around 1300 W/(m·K) at 300 K. The basic physical properties of cubic BAs have been experimentally measured: Band gap (1.82 eV), optical refractive index (3.29 at wavelength 657 nm), elastic modulus (326 GPa), shear modulus, Poisson's ratio, thermal expansion coefficient (3.85×10⁻⁶/K), and heat capacity. It can be alloyed with

gallium arsenide Gallium arsenide (GaAs) is a III-V direct band gap semiconductor with a zinc blende crystal structure. Gallium arsenide is used in the manufacture of devices such as microwave frequency integrated circuits, monolithic microwave integrated c ...

to produce ternary and quaternary semiconductors. BAs has high electron and hole mobility, >1000 cm²/V/second, unlike silicon which has high electron mobility, but low hole mobility.

Boron subarsenide

Boron arsenide also occurs as subarsenides, including the icosahedral boride . It belongs to ''Rm''

space group In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object that leave it uncha ...

with a

rhombohedral In geometry, a rhombohedron (also called a rhombic hexahedron or, inaccurately, a rhomboid) is a three-dimensional figure with six faces which are rhombi. It is a special case of a parallelepiped where all edges are the same length. It can be us ...

structure based on clusters of boron atoms and two-atom As–As chains. It is a wide-bandgap semiconductor (3.47 eV) with the extraordinary ability to "self-heal" radiation damage. This form can be grown on substrates such as

silicon carbide Silicon carbide (SiC), also known as carborundum (), is a hard chemical compound containing silicon and carbon. A semiconductor, it occurs in nature as the extremely rare mineral moissanite, but has been mass-produced as a powder and crystal s ...

. Another use for

solar cell A solar cell, or photovoltaic cell, is an electronic device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon.

fabrication was proposed, but it is not currently used for this purpose.

Applications

Boron arsenide is most attractive for use in electronics thermal management. Experimental integration with

gallium nitride 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 ...

transistors to form GaN-BAs heterostructures has been demonstrated and shows better performance than the best GaN

HEMT A high-electron-mobility transistor (HEMT), also known as heterostructure FET (HFET) or modulation-doped FET (MODFET), is a field-effect transistor incorporating a junction between two materials with different band gaps (i.e. a heterojunction ...

devices on silicon carbide or diamond substrates. Manufacturing BAs composites was developed as highly conducting and flexible thermal interfaces. First-principles calculations have predicted that the

thermal conductivity The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by k, \lambda, or \kappa. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal ...

of cubic BAs is remarkably high, over 2,200 W/(m·K) at room temperature, which is comparable to that of diamond and graphite. Subsequent measurements yielded a value of only 190 W/(m·K) due to the high density of defects. More recent first-principles calculations incorporating four-phonon scattering predict a thermal conductivity of 1400 W/(m·K). Later, defect-free boron arsenide crystals have been experimentally realized and measured with an ultrahigh thermal conductivity of 1300 W/(m·K), consistent with theory predictions. Crystals with small density of defects have shown thermal conductivity of 900–1000 W/(m·K). The cubic-shaped boron arsenide has been discovered to be better at conducting heat and electricity than

silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ...

, as well as reportedly better than silicon at conducting both electrons and its positively charged counterpart, the "electron-hole."

References

External links

* 2020 paper by Malica and Dal Corso
Temperature dependent elastic constants and thermodynamic properties of BAs: An ab initio investigationMatweb data
* *
High ambipolar mobility in cubic boron arsenide
Science {{Boron compounds Boron compounds Arsenides III-V compounds III-V semiconductors Zincblende crystal structure B