Probing the origin of abnormally strong electron-phonon interaction in phonon transport of semiconductor C3B monolayer

[Display omitted] •Strong EPI significantly reduces thermal conductivity in the C3B monolayer.•The reduction of κ induced by EPI is closely related to electron DOS.•The electronic band structure of C3B exhibits multivalley characteristics.•Unusual phenomenon of large el-ph scattering with low el-ph strength is uncovered.•The B atoms of C3B break structural symmetry and induce mass disorder scattering. Recently, the two-dimensional semiconductor C3B monolayer has attracted much attention owing to its excellent physical, optical, and electronic properties. In this work, the origin of electron-phonon interaction (EPI) on the thermal properties of C3B by n-type and p-type doping is systematically investigated via first-principles calculations to provide fundamental knowledge for the thermal management the C3B-based electronic devices. The carrier concentrations for the largest reduction of the lattice thermal conductivity (κ) appear at 4 × 1014 cm−2 for n-type and 9 × 1014 cm−2 for p-type, which is closely related to the electron density of states (DOS). The boron (B) atoms break the structural symmetry and induce mass disorder scattering, which renders C3B more prone to the influence of EPI. Moreover, the electronic band structure in the C3B monolayer exhibits multivalley characteristics, which leads to an intervalley scattering. It is worth noting that the anisotropy in the C3B monolayer can be significantly enhanced by EPI. Additionally, an abnormal phenomenon of strong electron-phonon scattering but low electron-phonon coupling strength is found in C3B monolayer, which indicates that large electron-phonon coupling strength is sufficient but not necessary for strong electron-phonon scattering.