Effect of intermixing at CdS/CdTe interface on defect properties

摘要

We investigated the stability and electronic properties of defects in CdTe_(1-x)S_x that can be formed at the CdS/CdTe interface. As the anions mix at the interface, the defect properties are significantly affected, especially those defects centered at cation sites like Cd vacancy, V_(Cd), and Te on Cd antisite, Te_(Cd), because the environment surrounding the defect sites can have different configurations. We show that at a given composition, the transition energy levels of V_(Cd) and Te_(Cd) become close to the valence band maximum when the defect has more S atoms in their local environment, thus improving the device performance. Such beneficial role is also found at the grain boundaries when the Te atom is replaced by S in the Te-Te wrong bonds, reducing the energy of the grain boundary level. On the other hand, the transition levels with respect to the valence band edge of CdTe_(1-x)S_x increases with the S concentration as the valence band edge decreases with the S concentration, resulting in the reduced p-type doping efficiency.