Uv-stimulated photocurrent spectroscopy and trapping kinetics of a 2.1-eV trap in anodic Ta2O5 films

Abstract

A new experimental technique, uv-stimulated photocurrent spectroscopy, has been used to study a trapping effect observed in the anodic oxide of sputtered β-Ta films. Experimental results indicate the presence of a discrete trap level peaked at 2.1 eV below the oxide conduction band, in addition to the 1.5-eV trap band as previously reported by Hickmott and later by Thomas. A kinetic model involving a single trap level in the oxide was used to analyze transient data. The results of this analysis indicate that the 2.1-eV trap is a positive Coulombic center having an electron capture cross section of 3.2×10−14 cm2, a photon capture cross section (at 2.1 eV) of 10−17 cm2, a density of states of 3×1018/cm3, and a ratio of filled to unfilled states of 0.06 during uv stimulation.