Insulating potential shape created by ultrathin silicon oxide layers

A previously developed method for reconstructing the insulating potential pattern created by an ultrathin silicon oxide layer from the field dependences of the tunneling current has been modernized. Trapezoidal model potential parameters, that provide the dependence of the current-to-voltage logarithm derivative as close as possible to the experimental one, have been calculated. The approach to starting successive iterations of the potential has been changed in such a way that the functions calculated using the model shape are used rather than zeroing the first turning point coordinates in zero-order approximation. The modernized algorithm has been applied to the experimental field current dependences in $n^+$-Si–SiO$_2$–$n$-Si structures with an oxide thickness of 3.7 nm, that have a pronounced asymmetry of the tunneling current-voltage characteristics with respect to the external voltage polarity. The effective potential barrier reconstructed from the experimental data is always significantly thinner than the insulating layer, with its maximum shifted towards the contact with the polycrystalline material, and the effective mass of the tunneling electron is several times greater than the typical for thick silicon oxide.