Phonon-mediated Optical and Electronic Transport Properties of BAs*

While boron arsenide (BAs) has attracted attention for its ultrahigh thermal conductivity, open questions remain about its use in semiconducting devices. To address this problem, we apply density functional and many body perturbation theory to understand its electronic and optical properties and guide device applications. Since BAs has an indirect band gap of approximately 2 eV and a direct gap of 4.1 eV, absorption of visible light is exclusively mediated by phonons. We therefore calculate the indirect and direct optical absorption spectra to assess its potential in photovoltaics and examine how excitonic effects alter the absorption. Our results are in excellent agreement with experimental data. We also calculate the effect of strain on the band alignment and the electron and hole mobilities, and show that bi-axial tensile strain increases the mobilities of both carriers by over 50%. Finally, we determine the band offsets of BAs heterostructures with nearly lattice-matched ZnSnN₂ and InGaN to guide heterostructure design. Our work elucidated the functional properties of BAs for technologically relevant device applications.