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 (V-O). V-O exists in the form of Cd-Zn-V-O complex, which can balance the strain caused by Cd-Zn and V-O. Due to high formation energy of the Zn interstitials (Zn-i) and deep transition energy level of V-O, Zn-i and V-O cannot serve singly as the source of the n-type carriers in Cd-dopped ZnO. It is also found that the Zn-i-Cd-Zn-V-O complex is a shallow donor like Zn-i, but has lower formation energy. Thus, the source of n-type carriers is believed to be a complex with Zn-i-Cd-Zn-V-O structures in Cd-doped ZnO. (c) 2010 Elsevier Masson SAS. All rights reserved.