Numerical analysis of packetlike charge behavior in low-density polyethylene by a Gunn effectlike model

Under some conditions, charges may transport like an isolated packet in polyethylene. It has been demonstrated that many factors, such as applied field strength, temperature, and material itself, influence on formation and migration of space charge packet, which cause many difficulties in understanding the general mechanism of the phenomenon. In this paper, based on the analysis about the influences of charge injection, carriers' migration, and the interaction between the free charge and trap in polyethylene on packetlike space charge behavior, a new physical model is established to give a physical description of packetlike charge behavior in low density polyethylene (LDPE). This model includes some interesting features: (1) it gives an exact calculation of charge changes in all positions of specimens; (2) the negative differential mobility mechanism of Gunn effect in semiconductor is introduced to explain the generating process of space charge packet; (3) field-induced charge detrapping model is utilized to simulate the diversity of packetlike charge packet behavior under different applied fields. By considering such a model, we simulate two kinds of positive packetlike charge behavior in LDPE from different research groups. The simulated results show well fitting with the experiment data. (C) 2011 American Institute of Physics. [doi:10.1063/1.3532052]