Photoluminescence reveals point-defect evolution associated with dielectric reliability in ferroelectric ZnMgO thin films

The dielectric reliability of wurtzite ZnMgO thin-film capacitors is closely associated with intrinsic donor defects, such as singly ionized oxygen vacancies and zinc interstitials; however, the relationship between the evolution of point defects and dielectric reliability remains insufficiently understood. Here, ZnMgO films were independently deposited at different cumulative sputtering times while the other deposition parameters were maintained constant, enabling systematic investigation of the relationship between defect evolution and electrical performance. Photoluminescence and x-ray photoelectron spectroscopy analyses revealed a redistribution of defect-related components, progressive suppression of donor-type defect-related signals, and stabilization of the near-surface chemical environment with increasing cumulative sputtering time. These changes were accompanied by lower leakage currents and improved breakdown reliability, with the characteristic breakdown field increasing from 2.36 to 3.22 MV/cm. In addition, the EBD/EC ratio increased from below 1.0 to approximately 1.4, expanding the electric-field window available for polarization switching. Within this enlarged window, distinct polarization-switching current peaks were observed in the I–E curves, and a dynamic ferroelectric response was detected in the P–E and PUND measurements for the 48 h sample. These findings highlight a sample-level correlation among point-defect evolution, dielectric reliability, and ferroelectric response in wurtzite ZnMgO thin films.