Injection of holes from the silicon substrate in Ta2O5 films grown on silicon

Abstract

In this paper a compact model for leakage currents of metal∕Ta2O5∕SiO2∕Si structures is presented, considering tunneling and hopping conduction in a SiO2 layer and Poole-Frenkel emission in a Ta2O5 layer. Theoretical calculations fit very well the experimental results obtained on thermally grown Ta2O5 films over an unintentionally grown ultrathin SiO2 layer for both bias polarities. The following parameters were fitted: the SiO2 layer thickness, the hopping conductivity of a SiO2 layer, and the Poole-Frenkel defect-related constant. Experimentally observed asymmetry between different polarities was explained by the injection of holes from the silicon substrate at negative bias.