Influence of intrinsic defects in CdTe and CdZnTe on the microstructure, magnetic, and optical properties of the system

Intrinsic defects can have an effect on the microstructure of semiconductor materials, which can change the electronic structure of the material and ultimately alter its optical and magnetic properties. In this study, first-principles calculations are performed to demonstrate that the defect formation energies of VTe and ZnCd + VTe are lower under Cd-rich conditions. Conversely, under Te-rich conditions, with the exception of Tei, the defect formation energies for TeCd, VCd, ZnCd + TeCd, and ZnCd + VCd are lower, indicating that these defects exhibit greater stability within the system. Furthermore, it is demonstrated that VCd, CdTe, and TeCd introduce magnetic moments into the CdTe system, with VCd contributing the largest magnetic moment. Additionally, composite defects formed by ZnCd and VCd, CdTe, and TeCd also induce spin polarization and introduce magnetic moments. However, the synergistic effect of ZnCd on CdTe defects is significant, reducing the magnetic moment introduced by the CdTe defects. Moreover, ZnCd + VTe composite defects, VTe + VCd composite defects, and VTe, Cdi, and Tei do not introduce magnetic moments into the system. For the CdTe and ZnCd + CdTe defect systems, there is a notable impact on the optical properties, such as the refractive index and reflectance, compared to the perfect CdTe system. When CdTe defects are present, defect energy levels are introduced within the bandgap, affecting electronic transitions between energy bands, which, in turn, influences the magnetic and optical properties of the system. Additionally, it is found that the optical properties of CdTe systems containing intrinsic or composite defects are isotropic, exhibiting weak absorption in the visible light range. However, VTe and TeCd defects can enhance the absorption of visible light to some extent.