Two-dimensional GaO monolayer with tunable band gap and high hole mobility.

By means of density functional theory and unbiased structure search computations, we systematically investigated the stability and electronic properties of a new Ga2O2 monolayer. The phonon spectra and ab initio molecular dynamics simulations show that the Ga2O2 monolayer is dynamically and thermally stable. Moreover, it also shows superior open-air stability. In particular, the Ga2O2 monolayer is an indirect semiconductor with a wide band gap of 2.752 eV and high hole mobility of 4720 cm2 V-1 s-1. Its band gap can be tuned flexibly in a large range by applied strain and layer control. It exhibits high absorption coefficients (>105 cm-1) in the ultraviolet region. The combined novel electronic properties of the Ga2O2 monolayer imply that it is a highly promising material for future applications in electronics and optoelectronics.