  This paper investigates strain effects on the electronic and optical
properties of monolayer GaSe using first-principles calculations. The
deformation significantly alters energy dispersion, band gap, and the band edge
states of GaSe. The band gap evolution exhibits both linearly and nonlinearly
with the strains, and strongly depending on the types of deformation and the
direction of the modifications. The external mechanical strains also
significantly tailor the optical properties of GaSe, the exciton binding energy
is strongly reduced when the tensile strain is applied, while the opposite way
is true for compressive stress. Moreover, the inhomogeneous strain also induces
strong polarization in the absorption spectra. Our calculations demonstrate
that the electronic and optical properties of GaSe monolayer can be
significantly tuned by using strain engineering which appears as a promising
way to design novel optoelectronic devices.
