 Neglecting every kind of diffusion process for the de-trapped carriers, the pre-exponential factor in the Poole-Frenkel formula is thus proportional to formula_30.This depiction would be suitable for the description of the conduction either in dielectrics or semiconductors.However, Poole-Frenkel effect is likely to be observed only in materials charcterized by low mobility values, for, in high mobility solids, the re-trapping of carriers would be gradually inhibited by carrier depletion.