Native Point Defects in Monolayer Hexagonal Boron Phosphide from First Principles

In this paper, we have investigated the electronic and magnetic properties of four types of native defects under neutral and charged states in a hexagonal boron phosphide (h-BP) monolayer, including boron vacancy (V_B) , phosphorus vacancy (V_P) , boron on the phosphorus site (B_P) and phosphorus on the boron site (P_B) within the framework of the density functional theory. For the four types of defects, various charge states were investigated, and only 0 and 1 + charge states for all defects are stable within the electronic chemical potential range (i.e. Fermi level range). It is found that B_P with the smallest defect formation energy is the most stable defect under both phosphorus-rich and -poor conditions in the whole range of electronic chemical potential. V_P and P_B are found to be shallow donors (i.e. 1 +/0) but could not be effectively introduced into the h-BP monolayer due to a rather high formation energy, while V_B and B_P are found to be holes trap centers. Especially, B_P with a low defect formation energy, will be produced easily and seriously affect the p-type doping efficiency and conductivity of h-BP. Additionally, V_B and V_P induce a nonzero magnetic moment while P_B and B_P show non-magnetic nature in the h-BP monolayer.