Strain and Electric Field Modulated Indirect to Direct Band Transition of Monolayer GaInS2

Abstract Strain and electric field dependent electronic and optical properties have been calculated using density functional theory (DFT) and time-dependent DFT (TD-DFT) for GaInS2 monolayer. GaInS2 monolayer shows an indirect band gap of 1.79 eV where valance band maxima (VBM) and conduction band maxima (CBM) rest between K and Γ point and at Γ point, respectively. Under a particular tensile strain (8%), a phase change from semiconductor to semimetal has been noticed. While at 4% compressive strain, the material changes from indirect to direct band gap of 2.22 eV having VBM and CBM at Γ point. With further increase in compressive strain, CBM shifted from Γ to M point, which leads to an indirect band gap again. The electric field also affects the band structure of monolayer GaInS2 and shows the transition between indirect to direct band gap at positive electric field of 4 V/nm, which acts normal to the surface. The strain-dependent optical properties are also calculated, which suggests that the absorption coefficient increases with compressive strain.