Tunable Properties of Novel Ga2O3 Monolayer for Electronics and Optoelectronics Applications.

A novel 2D Ga2O3 monolayer was constructed and systematically investigated by first-principles calculations. The 2D Ga2O3 has an asymmetric configuration with the quintuple-layer atomic structure, the same with the well-studied α-In2Se3, and is expected to be experimentally synthesized. The dynamic and thermodynamic calculations show excellent stability properties for this monolayer material. The relaxed Ga2O3 monolayer has an indirect band gap of 3.16 eV, smaller than that of β-Ga2O3 bulk, and shows tunable electronics and optoelectronics properties with biaxial strain engineering. An attractive feature is that the asymmetric configuration spontaneously introduces an intrinsic dipole and thus the electrostatic potential difference between the top and bottom surfaces of Ga2O3 monolayer, which helps to separate photon-generated electrons and holes within the quintuple-layer structure. By applying compressive strain, the Ga2O3 monolayer can be converted to a direct band gap semiconductor with a wider gap reaching 3.5 eV. Also, enhancement of hybridization between orbitals leads to the increase of electron mobility, from the initial 5000 cm2V-1s-1 increasing to 7000 cm2V-1s-1. Excellent optical absorption ability is confirmed, which can be effectively tuned by strain engineering. With the superior stability, as well as the strain-tunable electronic properties, carrier mobility and optical absorption, the studied novel Ga2O3 monolayer sheds light on low-dimensional electronic and optoelectronics device applications.