Wurtzite boron arsenide polytypes for polarization-controlled optoelectronic devices: a first principles study

Cubic boron arsenide (c-BAs) is a promising semiconductor exhibiting high thermal conductivity and carrier mobility, making it a potential building block for next-generation electronic and optical devices designed to efficiently manage heat degradation. While c-BAs is the most stable structure, the wurtzite form of BAs has recently been synthesized, opening new avenues for applications that exploit its intrinsic uniaxial symmetry. This breakthrough potentially enables the synthesis of other wurtzite polytypes, as observed in other group III–V semiconductors. Here, we employ excited-state density functional theory to study the vibrational, electronic, and optical properties of the 2H, 4H, and 6H wurtzite polytypes of BAs, including quasi-particle and excitonic effects. The results indicate that the studied polytypes exhibit indirect electronic band gaps ranging from 2.05 to 2.15 and exciton binding energies that are between two and three-times greater than the room temperature energy. Our findings elucidate the role of light polarization due to its uniaxial symmetry, demonstrating that it is possible to observe optical and vibrational fingerprints that enable distinguishing among the BAs polytypes. These findings suggest the potential application of wurtzite BAs polytypes in polarization-controlled optoelectronics.