Many-body perturbation theory analysis of point defects in bulk and monolayer semiconducting materials

Defects can strongly influence the electronic properties of semiconducting materials. An accurate and detailed knowledge of the influence of defects is central to the design of new high-performance materials. We employ first-principles many-body perturbation theory within the GW/BSE approximation to investigate the influence of point defects on the electronic properties of bulk and monolayer semiconducting materials. For a +1 charged nitrogen vacancy within bulk GaN, we develop an approach to systematically identify defects and their energies from GW/BSE calculations. By analysis of the bandstructure and optical absorption spectrum, we predict that this particular defect does not significantly alter the optoelectronic properties of GaN. Furthermore, the same methodology is applied to monolayer WS₂ containing a single sulfur vacancy, a likely point defect in this TMDC. We determine that the electronic properties relevant to transport in WS₂ are significantly affected by the presence of this defect, with implications for devices fabricated using this material system.