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

Two-dimensional (2D) Bi2O2Se has been widely used as optoelectronic detectors due to its excellent carrier mobility and environmental stability. However, the synthesis of the p-type Bi2O2Se 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 Bi2O2Se using first-principles calculations. The results indicate that Se vacancy (VSe) and O vacancy (VO) are shallow donors, which lead to the n-type Bi2O2Se semiconductor. Ca substituting Bi (CaBi) and Cd substituting Bi (CdBi) are accepters and can compensate the n-type behavior of shallow donors. The compensation effect of CdBi is weaker than that of CaBi due to its higher formation energies. Additionally, the calculation results of the Fermi level, defect and carrier concentrations indicate that CaBi shifts the Fermi level towards the valence band maximum (VBM), however, it is not sufficient to convert Bi2O2Se into the p-type.