Study on interactions between Cadmium and defects in Cd-doped ZnO by first-principle calculations

An ab initio calculation based on density functional theory is applied to study the formation energy and transition energy level of defects and complexes in Cd-dopped ZnO. The calculation shows that the incorporation of Cd into ZnO leads to the increase of the O vacancies (VO). VO exists in the form of CdZn–VO complex, which can balance the strain caused by CdZn and VO. Due to high formation energy of the Zn interstitials (Zni) and deep transition energy level of VO, Zni and VO cannot serve singly as the source of the n-type carriers in Cd-dopped ZnO. It is also found that the Zni-CdZn-VO complex is a shallow donor like Zni, but has lower formation energy. Thus, the source of n-type carriers is believed to be a complex with Zni-CdZn-VO structures in Cd-doped ZnO.

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