Strain-tunable electronic structure, optical response, and high electron mobility of Bi2O2Se crystals

Abstract

Newly fabricated semiconductor Bi2O2Se films exhibit excellent electron transport and optical properties, with potential application in optoelectronics. In this work, using first-principle calculations combined with the modified Becke-Johnson exchange potential, we have systematically investigated the electronic, transport, and optical properties of bulk Bi2O2Se. Our calculations have shown that external strain can effectively tune the bulk Bi2O2Se electronic bandgap and optical response and that, in particular, the appropriate strain can lead to a transition from an indirect to a direct bandgap. In addition, we found that electron mobility increased with Bi2O2Se crystal thickness and that the computed bulk Bi2O2Se acoustic-phonon-limited electron mobility could reach ∼940 and 535 cm2 V−1 s−1 in the a(b) and c directions at 300 K—which was much higher than that (∼50 cm2 V−1 s−1) achieved by the monolayer. There was a clear anisotropy of the electron mobility in bulk Bi2O2Se, which could be attributed to the synergistic effect between the elastic modulus anisotropy and the deformation potential. Our results not only have given new insight into the high carrier mobility of different thickness Bi2O2Se films (monolayer to bulk) but have also revealed the importance of the electron-transport direction to device performance. Together with the high carrier mobility, strain-tunable electronic structure, and optical response, Bi2O2Se films with different thicknesses have been shown to be very attractive for application to optoelectronic and electronic devices.