Hybrid functional calculations of electronic and thermoelectric properties of GaS, GaSe, and GaTe monolayers.

Motivated by the recent success in the experimental synthesis of two-dimensional group-III monochalcogenides, we investigate the structural, electronic and thermoelectric properties of GaS, GaSe and GaTe monolayers based on the first-principles approach by using density functional theory and the semi-classical Boltzmann transport equation. The electronic band structures demonstrate that the GaS, GaSe, and GaTe monolayers are wide bandgap semiconductors having an indirect bandgap of 3.73 eV, 3.27 eV, and 2.46 eV respectively. We have evaluated the thermoelectric properties comprising the Seebeck coefficient, electrical conductivity per relaxation time, electronic thermal conductivity per relaxation time, electronic specific heat, thermoelectric figure of merit and power factor at various temperatures from 50 K to 800 K. It is found that GaS, GaSe and GaTe monolayers could be suitable candidates for low temperature efficient thermoelectric materials because of the high value of the thermoelectric figure of merit below room temperature.