Nontrivial role of polar optical phonons in limiting electron mobility of two-dimensional Ga2O3 from first-principles

Abstract

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.