Logarithmic detrapping response for holes injected into SiO2 and the influence of thermal activation and electric fields

Abstract

Relaxation of trapped holes that are introduced into silicon dioxide from silicon by the avalanche injection method is studied under various conditions of thermal activation and external electric fields. It is found that the flat band voltage recovery in time follows a universal behavior in that the response at high temperatures is a time scaled extension of the response at low temperatures. Similar universality exists in the detrapping response at different external bias fields. The recovery characteristics show a logarithmic time dependence in the time regime studied (up to 6000 s). We find that the recovery is thermally activated with the activation energy varying from 0.5 eV for a field of 2 MV/cm to 1.0 eV for a field of −1 MV/cm. There is little discharge in 3000 s at room temperature for negative fields beyond −4 MV/cm. The results suggest that the recovery is due to tunneling of electrons in the silicon conduction band into the oxide either to compensate or to remove the charge of trapped holes.