On the current conduction mechanisms of CeO2/La 2O3 stacked gate dielectric

It was found that the electrical properties of CeO₂/La ₂O₃ stack are much better than a single layer La ₂O₃ film. A thin CeO₂ capping layer can effectively suppress the oxygen vacancy formation in the La₂O ₃ film. This work further investigates the current conduction mechanisms of the CeO₂ (1 nm thick)/La₂O₃ (4 nm thick) stack. Results show that this thin stacked dielectric film still has a large leakage current density; the typical 1-V leakage can exceed 1 mA/cm ² at room temperature. The large leakage current should be due to both the oxide defect centers as well as the film structure. Results show that at low electric field (2 film which has a higher k value than that of the La₂O₃ film. At higher electric fields, the current conduction is governed by Poole-Frenkel (PF) emission via defect centers with an effective energy level of 0.119 eV. The temperature dependent current-voltage characteristics further indicate that the dielectric defects may be regenerated as a result of the change of the thermal equilibrium of the redox reaction in CeO₂ film at high temperature and the drift of oxygen under the applied electric field. © 2013 Elsevier Ltd. All rights reserved.