Engineering of optical and electrical properties of ZnO by non-equilibrium thermal processing: The role of zinc interstitials and zinc vacancies

A controlled manipulation of defects in zinc oxide (ZnO) and the understanding of their electronic structure can be a key issue towards the fabrication of p-type ZnO. Zn vacancy (V-Zn), Zn interstitials (I-Zn), and O vacancy (V-O) are mainly native point defects, determining the optoelectronic properties of ZnO. The electronic structure of these defects still remains controversial. Here, we experimentally demonstrate that the green emission in ZnO comes from V-Zn-related deep acceptor and V-Zn-V-O clusters, which is accompanied by the radiative transition between the triplet and the ground singlet state with the excited singlet state located above the CB minimum. Moreover, the I-Zn is identified to be a shallow donor in ZnO, being mainly responsible for the n-type conductivity of non-intentionally doped ZnO.