Large variation of electron-phonon coupling and thermal transport in two-dimensional semimetal triphosphides by modulation doping

Recent studies demonstrated that novel two-dimensional (2D) triphosphide semiconductors possess high carrier mobility and show promising thermoelectric performance, but the carrier transport behaviors in 2D semimetal triphosphides have never been elucidated. Herein, using first-principles calculations and Boltzmann transport theory, we reveal that the electron-phonon coupling effect induced by increasing electron concentration can be significant and thus greatly inhibits electron and phonon transport in electron-doped BP3 and CP3. The intrinsic heat transport capacity of flexural acoustic phonon modes in the wrinkle structure is largely suppressed because of the strong phonon scatterings, leading to the low phonon thermal conductivities of 1.36 and 5.33 W/(m K) for BP3 and CP3 at room temperature, and at high doping level, the enhanced scattering from the electron diminishes the phonon thermal conductivity by 71% and 54%, respectively. Instead, electron thermal conductivity shows nonmonotonic variations with the increase of doping concentration, stemming from the competition between electron-phonon scattering rates and electron group velocity. Notably, the heavy-doping effect induced by strong scattering from the phonon largely suppresses the electron transport and reduces electron thermal conductivity to the magnitude of phonon thermal conductivity. This work sheds light on the electron and phonon transport properties in semimetal triphosphide monolayers and provides an efficient avenue for the modulation of carrier transport by the doping-induced electron-phonon coupling effect. © 2023 American Physical Society.