Boron arsenide (or Arsenic boride) 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.
Properties
BAs is a cubic (
sphalerite)
semiconductor in the
III-V family with a
lattice constant of 0.4777 nm and an
indirect band gap of 1.82 eV. Cubic BAs is reported to decompose to the subarsenide B12As2 at temperatures above 920 °C.[5] 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 to produce ternary and quaternary semiconductors.[6]
BAs has high electron and hole mobility, >1000 cm2/V/second, unlike silicon which has high electron mobility, but low hole mobility.[7]
In 2023, a study in journal
Nature reported that subjected to high pressure BAs decrease its thermal conductivity contrary to the typical increase seen in most materials.[8][9][10]
Boron subarsenide
Boron arsenide also occurs as subarsenides, including the
icosahedral boride B12As2. It belongs to R3mspace 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.[11] This form can be grown on
substrates such as
silicon carbide.[12] Another use for
solar cell fabrication[6][13] 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 transistors to form GaN-BAs heterostructures has been demonstrated and shows better performance than the best GaN
HEMT devices on silicon carbide or diamond substrates. Manufacturing BAs composites was developed as highly conducting and flexible thermal interfaces.[14]
First-principles calculations have 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.[15] Subsequent measurements yielded a value of only 190 W/(m·K) due to the high density of defects.[16][17] More recent first-principles calculations incorporating four-phonon scattering predict a thermal conductivity of 1400 W/(m·K).[18] 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).[19][20]
The cubic-shaped boron arsenide has been discovered to be better at conducting heat and electricity than
silicon, as well as reportedly better than silicon at conducting both electrons and its positively charged counterpart, the "electron-hole."[21]
^Morosin, B; Aselage, T. L; Feigelson, R. S (2011). "Crystal Structure Refinements of Rhombohedral Symmetry Materials Containing Boron-Rich Icosahedra". MRS Proceedings. 97.
doi:
10.1557/PROC-97-145.
^Chu, T. L; Hyslop, A. E (1974). "Preparation and Properties of Boron Arsenide Films". Journal of the Electrochemical Society. 121 (3): 412.
Bibcode:
1974JElS..121..412C.
doi:
10.1149/1.2401826.
^
abGeisz, J. F; Friedman, D. J; Olson, J. M;
Kurtz, Sarah R; Reedy, R. C; Swartzlander, A. B; Keyes, B. M; Norman, A. G (2000). "BGaInAs alloys lattice matched to GaAs". Applied Physics Letters. 76 (11): 1443.
Bibcode:
2000ApPhL..76.1443G.
doi:
10.1063/1.126058.
^Chen, H.; Wang, G.; Dudley, M.; Xu, Z.; Edgar, J. H.; Batten, T.; Kuball, M.; Zhang, L.; Zhu, Y. (2008). "Single-Crystalline B12As2 on m-plane (1100) 15R-SiC". Applied Physics Letters. 92 (23): 231917.
Bibcode:
2008ApPhL..92w1917C.
doi:
10.1063/1.2945635.
hdl:2097/2186.
^Boone, J. L. and Vandoren, T. P. (1980) Boron arsenide thin film solar cell development, Final Report, Eagle-Picher Industries, Inc., Miami, OK.
abstract.