Electron doping limit in Al-doped ZnO by donor-acceptor interactions

We investigate the maximum available free electron carrier density in Al-doped n-type ZnO, based on density-functional theory calculations. The Coulomb interactions between the Al dopants and the Zn-vacancy native acceptors are found to limit the carrier density. In typical growth conditions, the n-type doping limit is found to be in the range of 1019 ∼ 1021 cm−3.