A Study of Monte Carlo Simulation for Negative Field Dependent Charge Mobility in Polymer Based on Disorder Model

Dynamics of packet-like space charges in low-density polyethylene under high electric fields can be reproduced by using a negative differential mobility. However, the mechanism of the negative differential mobility has not been clarified. In this study, to investigate the mechanism of the negative differential mobility, we perform Monte Carlo simulations of charge motion using the Miller-Abrahams equation in the Gaussian disorder model. The calculated mobility shows a positive electric field dependence in a low electric field region. This is because an increase in the electric field lowers the barrier and increases the hopping probability in the direction of the electric field. On the other hand, in a high electric field region, it shows a negative electric field dependence. Under the high electric field, the hopping probability does not increase and the velocity of the charge saturates because there is no barrier preventing hopping even when the electric field is increased.