The p-type modulation of Bi₂O₂Se by Ca and Cd doping

Two-dimensional (2D) Bi 2 O 2 Se has been widely used as optoelectronic detector due to its excellent carrier mobility and environmental stability. However, the synthesis of the p -type Bi 2 O 2 Se remains challenging which hinders its further applications. In this paper, we have investigated the electronic properties of the native point defects and the Ca/Cd-doping effects on Bi 2 O 2 Se using first-principles calculations. The results indicate that Se vacancy (V Se ) and O vacancy (V O ) are shallow donors, which lead to the n -type Bi 2 O 2 Se semiconductor. Ca substituting Bi (Ca Bi ) and Cd substituting Bi (Cd Bi ) are acceptors and can compensate the n -type behavior of shallow donors. The compensation effect of Cd Bi is weaker than that of Ca Bi due to its higher formation energies. Additionally, the calculation results of the Fermi level, defect and carrier concentrations indicate that Ca Bi shifts the Fermi level towards the valence band maximum (VBM), however, it is not sufficient to convert Bi 2 O 2 Se into the p -type.