Native Point Defects in Monolayer Hexagonal Boron Phosphide from First Principles

Abstract

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 ( $$ V_{\rm{B}} ) $$ , phosphorus vacancy ( $$ V_{\rm{P}} ) $$ , boron on the phosphorus site ( $$ B_{\rm{P}} ) $$ and phosphorus on the boron site ( $$ P_{\rm{B}} ) $$ 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 $$ B_{\rm{P}} $$ 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. $$ V_{\rm{P}} $$ and $$ P_{\rm{B}} $$ 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 $$ V_{\rm{B}} $$ and $$ B_{\rm{P}} $$ are found to be holes trap centers. Especially, $$ B_{\rm{P}} $$ with a low defect formation energy, will be produced easily and seriously affect the p-type doping efficiency and conductivity of h-BP. Additionally, $$ V_{\rm{B}} $$ and $$ V_{\rm{P}} $$ induce a nonzero magnetic moment while $$ P_{\rm{B}} $$ and $$ B_{\rm{P}} $$ show non-magnetic nature in the h-BP monolayer.