Optical properties of cubic boron arsenide

The ultrahigh thermal conductivity of cubic boron arsenide (BAs) makes it a promising material for next-generation electronics and optoelectronics. Here, we report measured optical properties of BAs crystals, including the complex dielectric function, refractive index, and absorption coefficient in the ultraviolet, visible, and near-infrared wavelength range. The data were collected at room temperature using spectroscopic ellipsometry and transmission and reflection spectroscopy. We further calculated the optical response using density functional theory and many-body perturbation theory, considering quasiparticle and excitonic corrections. The computed values for the direct and indirect bandgaps (4.25eV and 2.07eV) agree well with the measured results (4.12eV and 2.02eV). Our findings pave the way for using BAs in future electronic and optoelectronic applications that take advantage of its demonstrated ultrahigh thermal conductivity and predicted high ambipolar carrier mobility.