Incipient Ferroelectric Transition Enables Ultrahigh Electron Mobility in Semiconducting Bi₂O₂Se

We find that the ultrahigh electron mobility observed in the layered semiconductor Bi₂O₂Se originates from an incipient ferroelectric transition that endows the material a large dielectric permittivity, providing it with a robust protection against mobility degradation by Coulomb scattering. Based on state-of-the-art first-principles calculations, we show that the low-temperature electron mobility of Bi₂O₂Se, taking into account both electron-phonon and ionized impurity scattering, can reach 10⁴to 10⁷cm²V⁻¹s⁻¹over a wide range of realistic doping levels. Moreover, a small elastic strain of 1.7% can drive Bi₂O₂Se toward the ferroelectric phase transition, inducing a giant increase in the permittivity and enables the strain-tuning of low-temperature electron mobility by more than an order of magnitude. These results establish a new route for realizing high-mobility<br/>layered semiconductors via phase and dielectric engineering.