Resolving the Puzzle of Charge Carrier Lifetime in ZnO by Revisiting the Role of Oxygen Vacancy
Yating Yang, Yitong Zhang, Sebastian Fernández-Alberti, Run Long
Abstract
Zinc oxide (ZnO) is a wide bandgap prototypical n-type semiconductor due to the presence of intrinsic oxygen vacancies (V O ). The V O can readily transfer to the most energetically favorable +2 charged V O (V O 2+ ) by losing two electrons mediated by the metastable V O 1+ defect. Nevertheless, the influence of charged V O on the charge dynamics in ZnO and the underlying mechanisms remain elusive. By performing nonadiabatic molecular dynamics simulations of the charge trapping and recombination processes, we show that both V O 1+ and V O 2+ slow down the nonradiative electron–hole recombination via assisted defect states and, thus, extending charge carrier lifetime compared to pristine ZnO. Our study contributes to identifying the different recombination pathways that take place in V O 1+ and V O 2+ of n-type ZnO systems, providing useful guidance for designing high-performance ZnO-based devices.