Simulation of leakage currents in (Ba,Sr)TiO3 thin films with extracted charge profile

Though many researchers have realized the importance of charge density and distribution to the leakage currents of (Ba,Sr)TiO3 (BST) thin films, till now, there has been no effective method of determining the charge profile of high-permittivity thin films directly. Most studies of the leakage currents of BST thin films are simply based on the assumption that the charge density is identical throughout the films. This is not an exact way to understand the nature of leakage currents. In this paper, we have extracted the charge profile from capacitance-voltage measurements and then used the combined model of thermionic emission and drift diffusion to simulate the leakage currents. Using the extracted charge profile, the thermionic emission and drift diffusion model, with almost all the parameters consistent with separate measurements or theoretical results, can fit the leakage characteristic of the BST film very well at medium-high fields and sufficiently high temperature. Based on the simulation results, the leakage conduction mechanism is determined reliably.