Basic Physical Properties of Cubic Boron Arsenide

TL;DR

This paper provides the first comprehensive experimental characterization of cubic boron arsenide's fundamental physical properties, including optical, mechanical, and thermal parameters, supported by theoretical calculations.

Contribution

It systematically measures key physical properties of BAs for the first time, combining experimental data with ab initio calculations to establish a foundational database.

Findings

Optical bandgap of 1.82 eV measured.

Refractive index of 3.29 at 657 nm.

Elastic modulus of 326 GPa, twice that of silicon.

Abstract

Cubic boron arsenide (BAs) is an emerging semiconductor material with a record-high thermal conductivity of 1300 W/mK. However, many fundamental properties of BAs remain unexplored experimentally. Here, for the first time, we report the systematic experimental measurements of important physical properties of BAs, including the bandgap, optical refractive index, stiffness, elastic modulus, shear modulus, Poisson ratio, thermal expansion coefficient, and heat capacity. In particular, light absorption and Fabry Perot interference were used to measure an optical bandgap of 1.82 eV and a refractive index of 3.29 (657 nm) at room temperature. A pico-ultrasonic method, based on ultrafast optical pump probe spectroscopy, was used to measure a high elastic modulus of 326 GPa, which is twice that of silicon. Furthermore, temperature dependent X-ray diffraction was used to measure a linear thermal expansion coefficient of 3.85x10^-6 per K; this value is very close to prototype semiconductors such as GaN, which underscores the promise of BAs for cooling high power and high frequency electronics. We also performed ab initio theory calculations and observed good agreement between the experimental and theoretical results. Importantly, this work aims to build a database (Table I) for the basic physical properties of BAs with the expectation that this semiconductor will inspire broad research and applications in electronics, photonics, and mechanics.