Two-dimensional cubic phase Ga2O3 with highly anisotropic mobility and robust wide-bandgap

Abstract

The electronic and transport properties of the two-dimensional (2D) cubic-Ga2O3 are systematically explored using Heyd–Scuseria–Ernzerhof (HSE) and Perdew–Burke–Ernzerhof functionals, as well as deformation potential theory, indicating the superior structural stability of the cubic monolayer compared with that of cleaved 2D β-Ga2O3. Accurate HSE calculation reveals an indirect bandgap of about 4.44 eV, which is composed of a flat valence band maximum with largely O-2p orbitals and a slight Ga-3d contribution as well as a dispersive conduction band minimum formed mainly by Ga-4s orbitals, illustrating that n-type conduction could be achieved. Applying ±6% strain modulation, the ∼10% bandgap change is observed due to the bond length variations. The calculated electron mobilities for unstrained 2D cubic-Ga2O3 are 1801.70 cm2 V–1s–1 along x direction and 240.78 cm2 V–1s–1 along y direction, which are comparable to those of perfect 2D β-Ga2O3 but are far exceed the values of bulk β-Ga2O3. Under +6% strain, electron mobilities increase to 3997.60 and 434.44 cm2 V–1s–1 along x and y directions, respectively. With ±6% biaxial strains, the mobility anisotropy is ranged from 6.92–9.20, which is substantially larger than the value of 1.82 in 2D β-Ga2O3 and indicating a strong directional dependence of electron transport at room temperature. The 2D cubic-Ga2O3 combines excellent anisotropic electron mobility, a stable bandgap and an intrinsically flexible structure, highlighting its considerable promise for nanoscale electronic device applications.