First-Principles Study of Intrinsic Point Defects of Monolayer GeSSupported by the National Natural Science Foundation of China (Grant Nos. 61922077, 11804333, 11704114, 11874347, 61121491, 61427901, 11634003, and U1930402), the National Key Research and Development Program of China (Grant Nos. 2016YFB0700700 and 2018YFB2200100), the Science Challenge Project (Grant No. TZ2016003), and the Youth Innovation Promotion Association of Chinese Academy of Sciences

Abstract

The properties of six kinds of intrinsic point defects in monolayer GeS are systematically investigated using the “transfer to real state” model, based on density functional theory. We find that Ge vacancy is the dominant intrinsic acceptor defect, due to its shallow acceptor transition energy level and lowest formation energy, which is primarily responsible for the intrinsic p-type conductivity of monolayer GeS, and effectively explains the native p-type conductivity of GeS observed in experiment. The shallow acceptor transition level derives from the local structural distortion induced by Coulomb repulsion between the charged vacancy center and its surrounding anions. Furthermore, with respect to growth conditions, Ge vacancies will be compensated by fewer n-type intrinsic defects under Ge-poor growth conditions. Our results have established the physical origin of the intrinsic p-type conductivity in monolayer GeS, as well as expanding the understanding of defect properties in low-dimensional semiconductor materials.