Single-Versus Multi-Step Trap Assisted Tunneling Currents-Part II: The Role of Polarons

Abstract

Using the framework developed in the first part of this work, we demonstrate the capabilities of the extended two-state model by reproducing leakage current characteristics of two selected technologies. First, we identify the temperature-activated leakage mechanism in /stacks using a tens of nanometer thick thermally grown oxide as through defects. Interestingly, this effect can be reproduced with the same parameters in a /stack with deposited oxide. Our simulations demonstrate that these charge transition centers are distributed within only a few nanometers from the /interface. The low thermal activation of the leakage current is linked to the low relaxation energies of the involved traps compared with those typically involved in and . Second, a similar mechanism can explain characteristics and transient charge trapping currents in capacitors with a insulating layer. By comparison of our model parameters to theoretical calculations, we identify self-trapped electrons (polarons) as a likely cause for these effects, as they have the required low relaxation energies.