Stability and electronic properties of two-dimensional Ga2O3 and (MxGa1-x)2O3 (M = Al, Ga) alloys

Abstract

The alloying of Ga2O3 monolayer with oxides of the same main group element (Al and In) is simulated by the special quasirandom structures method. The stability and electronic properties of the Ga2O3 monolayer and (MxGa1-x)2O3 monolayer alloys are systematically investigated by first-principles calculations. The (AlxGa1-x)2O3 monolayer alloy becomes more stable with the increase of Al2O3 content, but the stability of (InxGa1-x)2O3 monolayer alloy worsens with the increase of In2O3 content. The (AlxGa1-x)2O3 monolayer alloy has relatively better thermodynamic stability, which would be easily synthesized at room temperature. The orbital-projected band structure and charge density reflect that the effect of alloying Ga2O3 with Al2O3 and In2O3 on the electronic properties of materials is mainly on the conduction band. Interestingly, we find that the charge density of the VBM and CBM states for Ga2O3 monolayer and its monolayer alloys exhibit the characteristic of complete separation in real space, i.e., an abnormal carrier separation. Through the calculation of the band-gap bowings parameter, it is predicted that the band gap of the monolayer alloy can continuously be tuned in the range of 3.38 ∼ 7.02 eV. These results would shed some light on the application of the Ga2O3 monolayer and its monolayer alloys in optoelectronic devices.