 Among the others, Simmons has proposed an alternative to the classical model with shallow neutral traps and deep donors, capable to exhibit a bulk-limited conduction with a Schottky electric field dependence, even in presence of a Poole-Frenkel conduction mechanism, thus explaining the "anomalous Poole-Frenkel effect" revealed by Ta205 and SiO films.Models there exist that consider the presence of both donor and acceptor trap sites, in a situation called "compensation of traps".The model of Yeargan and Taylor, for example, extends the classical Poole-Frenkel theory including diverse degrees of compensations