Nontrivial Role of Polar Optical Phonons in Limiting Electron Mobility of Two-Dimensional Ga2O3 from First-Principles.

The exfoliated two-dimensional (2D) Ga2O3 opens new avenues to fine-tune the carrier and thermal transport properties for improving the electro-thermal performance of gallium oxide-based power electronics with their enhanced surface-to-volume ratios and quantum confinement. Yet, the carrier transport in 2D Ga2O3 has not been fully explored, especially considering their large Fröhlich coupling constants. Herein, we mainly investigate the electron mobility of monolayer (ML) and bilayer (BL) Ga2O3 from first-principles by adding polar optical phonon (POP) scattering. The results show that POP scattering is the dominant factor limiting the electron mobility for 2D Ga2O3, accompanied by a large 'ion-clamped' dielectric constant Δε. The value of Δε is 3.77 and 4.60 for ML and BL Ga2O3, respectively, indicating a large change in polarization in the external field. The electron mobility of 2D Ga2O3 enhances with increasing thickness despite the enhanced electron-phonon coupling strength and Fröhlich coupling constant. The predicted electron mobility for BL and ML Ga2O3 at a carrier concentration of 1.0 × 1012 cm-2 is 125.77 cm2 V-1 s-1 and 68.30 cm2 V-1 s-1 at room temperature, respectively. This work aims to unravel the scattering mechanisms beneath engineering electron mobility of 2D Ga2O3 for promising applications in high-power devices.