Field Dependent Carrier Transport Mechanisms in Metal-Insulator-Metal Devices with Ba_(0.8)Sr_(0.2)TiO_3/ ZrO_2 Heterostructured Thin Films as the Dielectric

摘要

Ba_(0.8)Sr_(0.2)TiO_3/ZrO_2 heterostructured thin films with different individual layer ZrO_2 thicknesses are deposited on Pt/Ti/SiO_2/Si substrates by a sol-gel process. The current versus voltage (Ⅰ-Ⅴ) measurements of the above multilayered thin films in metal-insulator-metal (MIM) device structures are taken in the temperature range of 310 to 410K. The electrical conduction mechanisms contributing to the leakage current at different field regions have been studied in this work. Various models are used to know the different conduction mechanisms responsible for the leakage current in these devices. It is observed that Poole-Frenkel mechanism is the dominant conduction process in the high field region with deep electron trap energy levels (φ_l) whereas space charge limited current (SCLC) mechanism is contributing to the leakage current in the medium field region with shallow electron trap levels (E_l). Also, it is seen that Ohmic conduction process is the dominant mechanism in the low field region having activation energy (E_a) for the electrons. The estimated trap level energy varies from 0.2 to 1.31 eV for deep level traps and from 0.08 to 0.18 eV for shallow level traps whereas the activation energy for electrons in ohmic conduction process varies from 0.05 to 0.17 eV with the increase of ZrO_2 sub layer thickness. An energy band diagram is given to explain the dominance of the various leakage mechanisms in different field regions for these heterostructured thin films.