Boron arsenide

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. 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. BAs is a cubic (sphalerite) semiconductor in the III-V family with a lattice constant of 0.4777 nm and an indirect band gap varying from 0.6 to 5.5 eV from different theory calculations. It can be alloyed with gallium arsenide to produce ternary and quaternary semiconductors. 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 is very high: around 1300 W/mK at 300 K. Boron arsenide also occurs as subarsenides, including the icosahedral boride B12As2. It belongs to R3m space group with a rhombohedral 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. Boron arsenide has been proposed as a material for solar cell fabrication, although it is not currently used for this purpose. An ab initio theory has predicted that the thermal conductivity 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 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/mK.