Transient and steady state currents in polyethylene, under low and high dc
voltages, are studied. In fact, a bipolar transport physical model is
developed in order to characterize the space charge dynamics within an
additive-free polyethylene film, under trapping and recombination
mechanisms. The numerical computational models, used for the bipolar
transport of carriers, are applied to the Poisson's, the continuity and the
transport equations with the appropriate physical conditions. The principal
and the new numerical results are calculated especially when high dc
voltages are applied. Indeed, the net charge density numerical profiles show
the appearance of the space charge packets that are revealed for the first
time in numerical modelling although they have long been reported in
experimental works. These space charge packets induce some new aspects on
the external transient current evolutions, produce the oscillations of the
conduction and the displacement current before the steady state, and
generate a conduction regime that is dominated by the interface
electrode-insulator. These numerical results are consistent with those
reported in some experimental works. However, under low dc voltage the space
charge packets disappear and the space charge limited current aspect appears
on the external current profile.