Indium doping-assisted monolayer Ga₂O₃ exfoliation for performance-enhanced MOSFETs

Monolayer (ML) Ga₂O₃ with outstanding properties is promising for advanced nanodevice applications; however, its high exfoliation energy makes obtaining it challenging. In this study, we propose a more efficient solution to obtain ML Ga₂O₃ by exfoliation from indium-doped bulk β-Ga₂O₃. The exfoliation efficiency with the assistance of In-doping and the doping influence on the stability and structural and electronic properties of ML Ga₂O₃ are systematically studied using first-principles calculations. The exfoliation energy of ML Ga₂O₃ is found to be reduced by 28% and is of the same order of magnitude as that of typical van der Waals (vdWs) 2D materials. Besides, excellent stability is preserved for ML Ga₂O₃ at extremely high In doping concentration by phonon spectrum and ab initio molecular dynamics inspections. The bandgap of ML Ga₂O₃ decreases from 4.88 to 4.25 eV with increased In concentration, and the modification of the VBM converts ML Ga₂O₃ to a direct bandgap semiconductor. With the suppression of ZA mode phonon scattering, the pristine and In-doped ML Ga₂O₃ exhibit high electron mobility, whereas the strong electron-phonon coupling (EPC) effect significantly decreases the hole mobility. Finally, the transfer characteristics of 5 nm MOSFETs based on the pristine and In-doped ML Ga₂O₃ with varied In concentrations are simulated based on the non-equilibrium Green's function (NEGF) formalism. The I_on for HP has a maximum of 3060 μA μm^-1 at In doping concentration of 5% and is triple that of the pristine ML Ga₂O₃ for LP at In doping concentration of 20%. The FOMs of n-type MOSFETs based on the In-doped ML Ga₂O₃ and typical 2D materials are compared and shows huge potential for sub-5 nm applications. Our study applies a new strategy for obtaining ML Ga₂O₃ and can also improve the device performance at the same time.