Atomic Mass Engineering of Ultra-High Thermal Conductivity in Large Bandgap Materials: A Case Study with Boron Arsenide

Heat dissipation highly relies on the thermal conductivity (\kappa) of materials. Materials with large bandgaps and significant atomic mass ratios, such as BAs, SiC, and \theta-TaN, have attracted considerable attention due to their potential for achieving ultra-high \kappa, with BAs serving as a particularly representative example due to its unique combination of large bandgap and high thermal conductivity. In this paper, the effects of atomic mass modification on phonon bandgap and \kappa are systematically investigated using a BAs model, accounting for both three- and four-phonon scattering processes. A 20 % increase in \kappa can be obtained by substituting B, achieved through widening the phonon bandgap, which suppresses phonon scattering. Notably, the AAOO four-phonon scattering channel is more suppressed than the AAO three-phonon channel, leading to an increased phonon lifetime (\tau). For As, \kappa can also be enhanced by 5\% when replaced by lighter atoms, such as ^69As, primarily due to the increased phonon group velocity (v). We systematically clarify how atomic-mass-induced bandgap variations affect \tau, v, and therefore \kappa in wide-bandgap systems. Our work provides a specific scheme for further improving the ultra-high \kappa of materials with large bandgaps, which possesses great guiding significance.