The effect of Al–Ta2O5 topographic interface roughness on the leakage current of Ta2O5 thin films

Amorphous Ta2O5 thin films were formed by radio-frequency magnetron sputtering at the substrate temperature of 200 °C. The electrical properties of Ta2O5 thin films were investigated as a function of the film thickness. The dominant conduction mechanism transited from the electrode-limited conduction (Schottky emission current) at low field to the bulk-limited conduction (Poole–Frenkel current) at high field. With increasing thickness of the thin films, the surface roughness increased, whereas the transition fields from the electrode-limited to the bulk-limited conduction process decreased. To verify the effect of this surface roughness on the electric conduction mechanism, a two-dimensional numerical simulator, MEDICI, was used to simulate the electric-field distribution at the bulk region of the thin film and the interface region between the thin film and the electrode.