Electrically Tunable Electronic and Optical Properties of Bilayer GaS

We employed first-principles calculations to investigate the geometric, electronic, and optical properties of bilayer GaS. Significant interlayer atomic interactions and a diverse range of multiorbital hybridizations result in various dispersion characteristics of energy bands, including numerous saddle points, band anticrossings, and partially flat subbands. The introduction of a perpendicular electric field (E-z) can manipulate the energy subbands, enhance the band anticrossings, induce additional saddle points and partially flat subbands, and trigger a semiconductor-metal transition. Spatial charge density distributions and projected density of states were utilized to elucidate the combined effects of interlayer atomic interactions and potential energy. The distinctive features of electronic properties manifest in optical absorbance, which exhibits a strong dependence on light polarization, the strength of E-z, and stacking sequence. The broad range of tunability in electronic and optical properties of bilayer GaS provides valuable insights for potential applications in optoelectronics.